Institut fürTechnische Informatik undKommunikationsnetze

3G Datalink for Wireless GPSSensorsSemester Thesis

Schnetzler Christoph

cschnetz@ethz.ch

Computer Engineering and Networks Laboratory

Department of Information Technology and Electrical Engineering

ETH Zurich

Supervisors:

Dr. Jan BeutelTonio Gsell

Prof. Dr. Lothar Thiele

June 11, 2018

Acknowledgements

I thank Jan Beutel, Tonio Gsell and Akos Pasztor for their support and theirhelpful inputs. I thank Thomas Kleier helping me vapor phase soldering theu-blox SARA-U270 modules.

i

Abstract

This semester thesis aims to extend the existing wireless GPS rev2 sensor sys-tem with a software interface for the cellular module. The goal is to exchangedata directly and reliably between the sensor system and the PermaSense databackend system. The result is a working, well-documented parser which handlesthe communication between the cellular module and the GPS sensor system. Itis able to establish an internet connection and can send and receive data over it.It is though not yet integrated in the existing wireless GPS sensor code.

ii

Contents

Acknowledgements i

Abstract ii

1 Introduction 1

2 Objectives 2

3 Overview 3

3.1 PermaSense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3.2 Wireless GPS rev2 sensor system . . . . . . . . . . . . . . . . . . 4

3.2.1 System overview . . . . . . . . . . . . . . . . . . . . . . . 4

3.2.2 Operating modes . . . . . . . . . . . . . . . . . . . . . . . 5

3.2.3 FreeRTOS . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4 Cellular module 7

4.1 Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4.2 AT commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.2.1 Operating modes . . . . . . . . . . . . . . . . . . . . . . . 8

4.2.2 Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.2.3 Response time . . . . . . . . . . . . . . . . . . . . . . . . 11

4.3 URC - Unsolicited Result Code . . . . . . . . . . . . . . . . . . . 11

4.4 Boot phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5 Code implementation 13

5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.2 Development environment . . . . . . . . . . . . . . . . . . . . . . 13

5.3 FreeRTOS primitives . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.3.1 Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

iii

Contents iv

5.3.2 Software timer . . . . . . . . . . . . . . . . . . . . . . . . 14

5.3.3 Event groups . . . . . . . . . . . . . . . . . . . . . . . . . 15

5.4 Cellular module software interface . . . . . . . . . . . . . . . . . 15

5.4.1 The AtCommand struct and the GSM struct . . . . . . . 15

5.4.2 UART and pin initialization . . . . . . . . . . . . . . . . . 16

5.4.3 AT command parser . . . . . . . . . . . . . . . . . . . . . 17

5.4.4 GSM task . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

5.5 Datalink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5.5.1 GPRS system architecture overview . . . . . . . . . . . . 25

5.5.2 Cellular network registration . . . . . . . . . . . . . . . . 25

5.5.3 Internal PDP context activation . . . . . . . . . . . . . . 27

5.5.4 Data connection . . . . . . . . . . . . . . . . . . . . . . . 27

6 Further work 29

6.1 Achieved goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6.2 Follow-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

7 Conclusion 31

Bibliography 32

List of figures 33

A WGPS Schematics 1

Chapter 1

Introduction

Avalanches, rockfalls and receding permafrost boundaries are just a few examplesof what is going on in the mountains. This leads us to the question if these eventsare predictable at all.

The PermaSense project has been working for years to record data suchas temperature, humidity, brightness, rock movements, etc., to create a betterunderstanding of the processes in the high alpine locations and to react early topossible natural hazards.

In order to collect data, sensors have been installed at some chosen locationsin the Alps which take measurements at regular intervals.

One of these sensors is the wireless GPS rev2 sensor. It collects groundmotion data and stores it either locally or sends it via a cellular module to thePermaSense data backend system. Up to now, these sensors can only store theirdata locally as the software interface for the cellular module is not implemented.

Therefore, the goal of this work is to implement an interface which is ableto establish a direct 3G datalink between sensor and PermaSense data backendsystem to exchange data.

1

Chapter 2

Objectives

• Extend the wireless GPS rev2 sensor system with a dedicated 3G datalink.

• Design an integration concept which guarantees

– efficient operation and monitoring of the system.

– reliable data transfer into the PermaSense data backend system.

• Implement and evaluate a prototype system based on the ARM/FreeRTOSsoftware framework of the wireless GPS rev2 sensor system.

• Document the work in a manner that follow-up projects can be built upon.

2

Chapter 3

Overview

3.1 PermaSense

The PermaSense project aims to observe and to understand the phenomena inhigh-alpine environments better. This can be, for instance, rockfalls, recedingpermafrost boundaries or slope instabilities. For a reliable observation of thephenomena, a sensing network has been developed. This network consists ofultra-low power wireless sensor nodes which are sensing a diverse range of pa-rameters, such as temperature, humidity, light, ground motion, etc. The nodesallow long term autonomous operations in range of multiple years. Therefore,the devices are strictly duty cycled and gather data in low rate (e.g. 1/120sec).Figure 3.1 shows the basic system architecture consisting of a Wireless SensorNetwork, Core Stations and the Data Backend.

Figure 3.1: PermaSense System Architecture [19]

3

3. Overview 4

3.2 Wireless GPS rev2 sensor system

The wireless GPS rev2 sensor system (WGPS) has been developed to measureground motion in high-alpine regions. Tracking ground motion helps to observerockfall and debris flow critical regions as well as the movement of boulders atsteep mountainsides. Having long time data over critical regions allows to detectsuspicious behaviors, such as accelerating motion or sudden movements. Forinstance, with such information, mountain villages located in danger zones canbe warned or evacuated at an early stage.

3.2.1 System overview

The WGPS device is driven by an ultra-low power STM32L496VG microcon-troller [2], based on an FPU ARM Cortex-M4 MCU. Its equipped with GPS,GSM, Radio (TinyNode), an electronic compass, a tilt, a temperature and ahumidity sensor (figure 3.2). The cellular module (called GSM) and the TinyN-ode are connected over a plug connection. Therefore, they can be plugged in ifneeded. It’s powered over a solar panel and needs between 11 and 20 voltageinput. The WGPS device is able to track ground motion with high precision inrange of millimeters. This precision is achieved by using a reference GPS sensormounted as closly as possible to the other sensors but at a position which isknown to be static (e.g. solid rock). If the other ones move, we can calculatethe relative movement which is much more precise than just the GPS data itself.The GPS data is recorded in raw format and no data processing is performedon the WGPS devices itself. The postprocessing is done in the PermaSense databackend system.

GPSCompass GSM

TiltSensor

HumiditySensor

Temp.Sensor

Buzzer Reed USB

Sense

DC/DC

Flash

TinyNode

MCU

Sense & Process Communication

Interfaces

Power Storage

Figure 3.2: WGPS System overview [14]

3. Overview 5

3.2.2 Operating modes

Compared to the basic system architecture (figure 3.1), the WGPS devices donot need any core stations, they directly connect to the PermaSense data back-end. This allows a simpler installation in the mountains. The WGPS has threedifferent operating modes.

StandaloneLogger

StandaloneCellular

GSM

Radio

Radio

GSM

NetworkMode

Radio

Radio

Figure 3.3: WGPS operating modes [14]

Standalone Logger Mode

In this operating mode, the WGPS device has no GSM and Radio module at-tached. Therefore, the device is not able to communicate with the PermaSensebackend system. It stores the measurements on its internal storage. The datahas to be extracted during on-site maintenance. This configuration is for areaswhich do not have cellular coverage or which are not intended to be observedonline.

Standalone Cellular Mode

The WGPS device is equipped with a cellular module but has no radio moduleattached. With the cellular module, the device is capable of communicatingwith the backend system. It can send the recorded measurements and receivecommands from the backend system.

Wireless Network Mode

This is the full configuration which uses radio and GSM. With the radio thedevice is able to communicate between multiple WGPS devices. One deviceacts as sink and collects all the date. This device is equipped with GSM andcan therefore forward all data to the backend system. The sink can also receivecommands from the backend which are forwarded over radio to the other devices.

3. Overview 6

Priorityx6

Priorityx5

Priorityx4

Priorityx3

Priorityx1

Priorityx2

Priorityx7

Priorityx0

InterruptsxrunningxatxthesexprioritiesxwillxneverxbexdelayedxfromxexecutingxbecausxofxanythingxthexFreeRTOSxkernelxisxdoing.

ISRsxthatxcallxAPIxfunctionsxendingxinxFFromISRFxcanxusexthesexinterruptxpriorities,xandxwillxnest.

Interruptsxthatxdoxnotx

callxanyxFreeRTOSx

APIxfunctionsxcanxusexallx

interruptxpriorities,x

andxwillxnest.

Figure 3.4: Example interrupt priority configuration [16]

3.2.3 FreeRTOS

The WGPS device needs to take measurements in periodic time steps. But notall measurements have to be done in the same periodic interval. Sometimes, ameasurement takes some time and we would like to do other work until it hasfinished and we can continue. We also want to be able to shut off the peripheralsindependently to save energy. We need something which organizes this largeamount of work for us. Therefore, the WGPS system uses FreeRTOS.

FreeRTOS is a real time operating system which is small enough to run onmicrocontrollers. It provides real time scheduling functionality, inter-task com-munication, timing and synchronization primitives. It allows us to write codein a set of independent tasks. Tasks reduce the dependencies between softwaremodules and increase the code maintainability. Each task and interrupt is as-signed to a priority which allows the scheduler to decide which task or interruptneeds to be executed first. As interrupts need to response very fast to events,they have always the higher priority than tasks. Means, the lowest interruptpriority is still higher than the highest task priority. Figure 3.4 shows a possibleinterrupt priority configuration where the maximal system call interrupt priorityis set to four and the kernel interrupt priority is set to zero. FreeRTOS has spe-cial API functions for interrupts, ending with ”FromISR”. These functions arelocated in the interrupt code, but not executed inside an ISR because FreeRTOSclaims to be deterministic and therefore doesn’t allow to call functions whichcould cause non-deterministic behavior.

The FreeRTOS primitives used in this project are introduced in section 5.3.

Chapter 4

Cellular module

The used cellular module is the SARA-U270 from u-blox [4].

Memory

V_BCKPl2RTC-

V_INTl2IxO-

RFtransceiver

PowerManagement

CellularBaseBandProcessor

ANT

VCCl2Supply-

USB

DDCl2IkC-

SIMlcardldetection

SIM

UART

PowerHOn

Reset

Digitallaudiol2IkS-

GPIO

Antennaldetection

3GlPA

k6lMHz

Duplexer

Filter

Switch

kGlPA

LNA

3klkHz

Figure 4.1: SARA-U270 block diagram [7]

4.1 Interface

The used serial communication interface is UART. The module features the com-plete functionality conforming to the ITU-T V.24 recommendation [5]. In theproject, only the data lines (Rx, Tx) and the hardware control lines (CTS, RTS)are used. The modem status and control lines (DTR, DSR, DCD, RI) are pro-vided but unused. By default, the HW flow control is enabled, the DSR line isset to ON in data mode and OFF in command mode and the module enters theonline command mode after an ON-to-OFF transition of the DTR line, issuingan ”OK” result code. Result codes are discussed in chapter 4.2.

The used frame format is 8N1 (8 data bits, no parity, 1 stop bit). 8N1 is alreadythe default frame configuration and doesn’t need to be changed.

7

4. Cellular module 8

4.2 AT commands

This section gives a short overview about AT commands. All information aboutu-blox AT commands can be found in the document “u-blox Cellular Modules -AT Commands Manual” [6].

4.2.1 Operating modes

The SARA-U270 module has three different operating modes:

• Command mode

• Data mode

• Online command mode

Command mode

In the command mode, the module interprets every received character as a com-mand to execute. Any communication in the command mode is terminated withthe command line termination character <s3 character>. By default, this is thecarriage return ’\r’ character. Every command has the following generic syntax:

"AT"<command_name><string><s3_character>

For instance,

"AT+IPR=9600\r"

but <string>can also be empty,

"AT+CGMM\r"

The AT command response comprises of an echo, an optional informationtext response string (ITR) and a final result code (FRC).

4. Cellular module 9

AT command

Echo

Information Text Response

Final Result Code

wait > 20 ms

next AT command

MCU Cellular Module

Figure 4.2: AT command response flow chart [17]

The echo is an exact copy of the command which has been sent. The ITRcontains intermediate outputs as well as descriptive outputs. This can be themanufacturer’s name, the firmware version, stored settings, etc. An ITR disposesof the following syntax:

<text><s3_character><s4_character>

The <s4 character>is by default the linefeed character ’\n’.

The FRC completes the response and informs about the result of the command.It has the following syntax:

<numerical_code><s3_character>

The most common FRC’s are “OK” and “ERROR”. All allowed result codesare listed in table 4.1. A possible response is, for instance:

AT+URAT?\r +URAT: 1,2\r\n 0\r

The module supports verbose or numeric responses. By default, the verboseresponse mode is enabled, but parsing text instead of numbers is inefficient.Therefore, we use the numeric response mode. After reception of the FRC oneshould wait for at least 20ms before issuing a new AT command. This allowsthe module to transmit buffered URC’s, otherwise collisions between URC’s andAT commands are possible. URC’s are introduced in section 4.3.

4. Cellular module 10

Verbose Numeric Description

OK 0 Command executed correctlyCONNECT 1 Data connection establishedRING 2 Incoming call signal from the networkNO CARRIER 3 Connection terminated from the remote

part or attempt to establish a connectionfailed

ERROR 4 General failureNO DIALTONE 5 No dialtone detectedBUSY 6 Called number is busyNO ANSWER 7 No hang up detected after a fixed network

timeoutCommand aborted 18 Command execution aborted

Table 4.1: Allowed result codes

Data mode

The Data mode is entered as soon as a connection to a remote host is establishedor the result code ”CONNECT” has been received, respectively. In this mode,the module doesn’t interpret characters to be commands. Instead, every charac-ter received from the serial interface is being forwarded to the remote host. Everycharacter received from the remote host is being forwarded to the serial interface.To exit the data mode, one needs to send +++. This triggers the module tosend ”OK”. Only after this message, the data mode is left successfully.

Online command mode

The online command mode is if the module is in data mode but can read andprocess AT commands. This mode can be entered over a ON-to-OFF transitionon the DTR line. An ”OK” result code indicates that the online command modehas been entered.

4.2.2 Errors

Every AT command has an error response type. The most common error typeis the ”+CME ERROR”. This error occurs if the issued command couldn’t beprocessed successfully by the cellular module. If an error occurs, the modulesends the echo followed by the FRC. By default, the FRC ”ERROR” is dis-played without information about what caused the failure exactly. The numericresponse for an error is 4. To enable the entire error message, one needs to sendthe AT command ”+CMEE” after the module has booted.

4. Cellular module 11

Next there is an example of an error response with +CMEE disabled,

AT+CPIN?\r ERROR\r

and with +CMEE enabled,

AT+CPIN?\r +CME ERROR: SIM NOT INSERTED\r

For a better understanding the example shows the verbose and not the numericresponse. In the numeric response ”ERROR” would be replaced with 4 and”SIM NOT INSERTED” with 10. All possible errors can be found in the ”ATCommands Manual, Appendix A” [6].

4.2.3 Response time

The cellular module usually replies immediately to an AT command. This meansthat in average it takes 10ms and in any case less than one second to respond.However, there are commands which will need more time to answer. For instance,the network registration can take up to three minutes until a response is issued.

4.3 URC - Unsolicited Result Code

Beside the normal response message, the module can as well send unsolicitedresult codes - URC’s (figure 4.3). URC’s are string messages which are completelyuncorrelated to an AT command execution. The module uses URC’s to informif a status changes or a specific event has occurred. This happens when, forinstance, the module has lost its network coverage and needs some time to registeragain to the network. URC’s can occur at any time except if the module is indata mode or if the module is already executing an AT command. URC’s needto be enabled with AT commands. Most of the URC’s have the same name asthe command that enables it. For instance,

AT+CREG=1

enables the network registration URC with the following appearance,

+CREG: 1

The One is just one possible value of CREG and indicates that the module isnow registered to the home network.

4. Cellular module 12

Unsolicited Result Code 1

Unsolicited Result Code 2

Unsolicited Result Code N

next AT command

Final Result Code

MCU Cellular Module

Figure 4.3: URC flow chart [17]

4.4 Boot phase

The boot phase of the module can take several seconds. In order to signal thesuccessful end of the boot phase, the module sends a greeting text. The modulewill not response to any AT commands before the greeting text has been sent.By default, the empty string is sent. The greeting text can be set to any stringwith a maximal length of 49 characters.If the greeting text is used, one needs to consider that the module has an au-tobauding feature which is enabled by default and allows the module to detectthe baudrate automatically as soon as the first characters have been received.Therefore, as long as the module hasn’t received anything, it won’t send any-thing. This means that if the greeting text is used to detect the end of thebooting phase, one needs to set a fix baudrate. Otherwise both sides wait for anevent that will never happen.In this project, the greeting text has been changed to “ready\r”.

Chapter 5

Code implementation

5.1 Overview

If the wireless GPS sensor system is not exactly operating in datalogger mode,it needs the cellular module to transfer the data to the PermaSense data back-end system. Up to now, the entire hardware is provided and also the softwareis complete except for the software interface between the cellular module andthe WGPS device. This means that actually the WGPS device if fully workingbut only in data logger mode. In this project we aim to close this gap and toimplement the interface. As mentioned in the objectives, the interface shouldallow efficient operation and give the opportunity to monitor the system.This chapter is split up in three major parts. In the first one, the developmentenvironment and the FreeRTOS primitives used in the implementation are in-troduced. In the second part, the interface will be explained more explicitly.And finally, in the third part, we consider how to establish a reliable connectionbetween cellular module and the PermaSense backend data system.

5.2 Development environment

The used development and debugging IDE is the Atollic R© TrueSTUDIO R© [1]for STM32 microcontrollers, based on Eclipse, CDT, GCC and GDB. It supportsversion control such as Git and the SEGGER J-Link [3] which has been used asdebugger. The entire project is version controlled using Git and the repositoryis stored on GitLab.

5.3 FreeRTOS primitives

As the rest of the already existing software relies on FreeRTOS, we need to imple-ment our interface within this framework. Our implementation uses FreeRTOS

13

5. Code implementation 14

tasks, software timers and event groups which are now introduced briefly. Moredetails can be found in the FreeRTOS reference manual [12].

5.3.1 Tasks

Tasks are the basic elements, handled by the scheduler. Each task can be in oneof four states (running, ready, blocked or suspend) as shown in figure 5.1. If atask is in blocking state, then he is not ready to run and waits for an event tohappen. If the event happens, the task is put in ready state by the scheduler. Ifit is the only task in ready state and no task is in running state, then the taskis immediately put in running state. Only in the running state, CPU time isconsumed. If more than one task is in ready state, the priority decides whichtask is put in running state first. If a task is suspended, it cannot resume byitself, instead, another task needs to do that. In our implementation we neveruse suspend as we always wait for some events to happen and therefore wait inblocked state.

vTaskSuspend()called

Ready

Event

Running

Blocked

Blocking APIfunction called

SuspendvTaskResume()

called

vTaskSuspend()called

vTaskSuspend()called

Figure 5.1: Valid task state transitions [15]

5.3.2 Software timer

FreeRTOS software timers are used to trigger an event in a certain time in thefuture. If one creates a timer, then one also needs to create a callback function.The callback function is called after the timer has fired and the code within thisfunction is executed. Timers can be used for various occasions. For instance, ifone starts to execute a measurement, but one does not know if the execution isdeterministic. A timer can be started before starting the execution and specifythe maximum allowed time the task has. If the task exceeds the specified time,the timer fires and can abort the execution.

5. Code implementation 15

5.3.3 Event groups

Event groups belong to the synchronization primitives and are used to commu-nicate events to tasks. They allow a task to stay in the blocked state until acombination of events has occurred. For instance, if we send an AT command,we need to wait for a response. This can be either the event “OK” or the event“ERROR”. Event groups allow us now to block the task until one of them oc-curs. In order to indicate if a certain event has occurred, event ‘flags’ are used.A set of events ‘flags’ is called event ‘group’. Setting an event flag or a certaincombination of them, unblocks the task.

5.4 Cellular module software interface

In the second step, we will now step through our implementation. First, weexplain two important control structures which are used in the entire code. Sec-ondly, we show how we initialized the serial interface between cellular module andMCU. Thirdly, we consider the command parser and explain how it is thoughtto be used. Finally, we introduce our task.

5.4.1 The AtCommand struct and the GSM struct

AtCommand struct

AT commands have different error types, response types, response times, sizesand names. This means that we need to handle the AT commands differentlyaccordingly to the given parameters. For instance, some take longer to respondthan others, some have only a FRC as response, some have an ITR followed bya FRC and there are also special cases where only an ITR is sent. In order tokeep track of all of these different characteristics, we created the AtCommandstruct. This struct stores the error type, the response type, the response time,the name and its size. Before sending an AT command, this struct has to befilled such that the parser (see section 5.4.3) is aware of what to expect and toreact accordingly.

GSM struct

This struct is the heart of our implementation. It contains the PARSER REGvariable. This variable is used as a register as every bit indicates a different parserstate. Table 5.1 lists all used flags. This register keeps track of the actual systemstate. At the very beginning, no bit is set. If we start to listen on the serialinterface, we activate the interrupt and then the first bit GSM IT ENABLED isset. Next, if we power on the cellular module, the second bit GSM RUNNING

5. Code implementation 16

Bit Name Description

0 GSM IT ENABLED Set if parser is started, interrupts enabled1 GSM RUNNING Set if module is activated2 GSM GREETING Set if greeting text has been received3 GSM COMMAND Set if response of a command is expected4 GSM URC Set if a URC is being received5 GSM ECHO OK Set if command echo from GSM Module is ok6 GSM FIRST AFTER ECHO Cleared if first character after echo is received7 GSM ERROR Set if error in the parser pipeline occurred

Table 5.1: PARSER Register

is set to indicate that from now on characters can be received. As we use thegreeting text to indicate a successful startup, we first need to wait for it to bereceived. The third bit GSM GREETING is set if we have received it. If thefirst three bits are set, we are ready to start sending AT commands.

During transmission and reception of an AT command, several errors canoccur. For instance, there can be an UART error, an error in the parser oran error response from the cellular module. Therefore, we store the error typeand its corresponding error code in the GSM struct. If an error is present, theGSM ERROR bit in the PARSER REG is set, also. This bit is set as long asthe error is not handled, and an error handling is pending.

The AT command responses and URC’s need to be stored somewhere. This isalso done in the GSM struct by using two pointers. One points to the beginningof the ITR string and the other one to the beginning of the URC string. Theyboth have stored their string size, too. The URC and the ITR pointer are usedin the URC Handler and in the Command Handler.

5.4.2 UART and pin initialization

All information about the STM32L496VG relies upon the information providedby the STM32L496 datasheet [8], the STM32L496 Reference Manual [9] and theSTM32 HAL driver [10] .

According to the wireless GPS rev2 sensor schematics, see Appendix, the cellu-lar module is connected over USART2. Therefore, Tx and Rx are on pin PA2and PA3 respectively. To initialize these pins, we use the UART HandleTypeDefstruct from the STM32 HAL driver. Because USART2 belongs to the alternatefunctions of a pin, we need to change its mode to AF7. In the next step, we needto initialize the UART itself. As mentioned in chapter 4.1, the cellular moduleuses the 8N1 frame format and therefore we set it accordingly to this. Table 5.2shows the entire setup. The baudrate has been set to 9600 bps but 115200 bps

5. Code implementation 17

UartHandle->Instance = USART2;UartHandle->Init.BaudRate = 9600;UartHandle->Init.WordLength = UART WORDLENGTH 8B;UartHandle->Init.StopBits = UART STOPBITS 1;UartHandle->Init.Parity = UART PARITY NONE;UartHandle->Init.HwFlowCtl = UART HWCONTROL RTS CTS;UartHandle->Init.Mode = UART MODE TX RX;UartHandle->Init.OverSampling = UART OVERSAMPLING 16;

Table 5.2: UART initialization

works as well.

Further, we need to select the clock source and enable the peripheral clockfor the USART2. Four different clocks can be used for USART2, PCLK, HSI16,LSE or the system clock SYSCLK. The clock source is set in the “Peripheralsindependent clock configuration register (RCC CCIPR)” and enabled with the“APB1 peripheral clock enable register (RCC APB1ENR1)”. In fact, one doesnot have to deal with these registers directly. The clock can be enabled with theHAL macro, HAL RCC USART2 CLK ENABLE() and the clock source canbe selected with the RCC PeriphCLKInitTypeDef struct. In the last step weset the interrupt priority of the USART2. This priority has to be chosen verycarefully to ensure that the entire system still works. The interrupt priority isset with HAL NVIC SetPriority() and enabled with HAL NVIC EnableIRQ().

5.4.3 AT command parser

The AT command parser (from now on called parser) is actually only an interrupthandler. Every time the USART2 interrupt is triggered, the parser is called.Figure 5.2 shows the entire structure. It can be split up in four parts as coloredin the figure. Every part will be explained briefly starting with the white section.

Entering interrupt handler

If the interrupt is triggered, we check if an UART error has occurred. If an erroris detected, we check if the cellular module (in figure 5.2 referred as GSM) isalready running. The GSM RUNNING flag indicates if the module is running.The flag is set as soon as the SW GSM pin (PE10) is set HIGH. This enables thevoltage supply for the cellular module. If the module is not running, this errorcan be ignored. If it is running, we call the UART error callback function. Theway how this error is handled needs to be adapted to the already existing code ofthe wireless GPS sensor system. For now, the callback function just restarts themodule. Without an UART error, we check if the cellular module is running andif there are unhandled errors from the parser or from the cellular module itself.

5. Code implementation 18

Interrupt Handler

UART Error?

GSM Running andno Unhandled Errors?

GSM Running?

Rx interrupt flags set?

UART Error Callback function

Error No Clear interrupt flag

YesNo Error

Yes

No

Read char from Register

Greeting message from GSMmodule received?

AT command response expected and no URC ongoing?

Echo ok?

Yes

Yes

No

Yes

No

Already charactersreceived?

NoNoStart timer, set URC flag

URC buffer full?

Command buffer full?

Yes

No

Clearbuffer

URC messagecomplete?

Yes

Match

No match

Yes

No

No match

Greeting text ok,Unblock GSM task

compare char with greeting text

compare char with echo

Parser Error,Unblock GSM task

echo ok,Unblock GSM taskMatch

Not finished

Not finishedYes

Not finished

URC complete,Unblock GSM task

Switch state

Wait for s3_character Info text response Final result code

Check if error has been received

Error,Unblock GSM task

Yes

No

No

Command ok,Unblock GSM task

Change state to ITR

No

s4_character received?

No

change state to FRC

No

length of FRC correct?

Yes

Yes

No

Is command type == FRC?

s3_character received?

Command ok,Unblock GSM task

Parser Error,Unblock GSM task

store char in buffer

Store char in buffer

No

Yes

Is command type== CONNECT?

Yes

s3_character received?

No

Yes

Yes

change state to ITR

Yes

Exit ISR

Stop timer, clear URC flag

URC

Command

GreetingText

Figure 5.2: AT command parser

5. Code implementation 19

Unhandled errors are indicated by the GSM ERROR flag. We only proceed ifthe module is running and no errors are pending. In the next step we check theRx interrupt flag to be sure that a new character has been received. If the flagis set, we read the character from the RDR register.

Now we have to decide where we need to compare this char. If the greetingtext of the cellular module hasn’t been received, then we enter the greeting textsection. If we have sent an AT command, then we expect the cellular moduleto response to it and the command section is entered. If no command responseis expected, we have an unsolicited result code (URC) from the module and theURC section is entered.

Greeting text

We use the greeting text to signal a successful boot (see chapter 4.4). It is sentas soon as the module is ready to receive AT commands. Why do we not handleit in the URC section as the greeting text is an URC? The reason why, is thatthe greeting text is the very first string we receive and therefore we check it atthe very beginning. This avoids sending AT commands before the greeting texthas been received.

In this part, we compare the received character with the corresponding char-acter from the greeting text. That means, if we receive, for instance, the 5thcharacter, then we compare it with the 5th character of our greeting text string.If it is correct and we are not at the end of our string, we leave and wait forthe next character to be received. If it doesn’t match, we set the GSM ERRORevent flag to unblock our GSM task. We also set the GSM ERROR flag in ourPARSER register to signal an unhandled error. If the last character of the greet-ing text has been received successfully, we set the GSM GREETING event flagto unblock the GSM task as well as the GSM GREETING flag in our PARSERregister. This flag is set as long as the module is not powered off or reset. If oneof these events take place, this flag needs to be cleared.

URC

URC’s have been explained in chapter 4.3. If no command response is expected,we enter this part of the implementation. First, we check if this is the firstcharacter we have received for the coming message. If this is true, we start aFree RTOS software timer and set the GSM URC flag in our PARSER registerto indicate that an URC is ongoing. The timer is set to ensure that the URCwill finish after some time and not hang up the parser. If the flag is already set,we don’t need to do it again and can continue. Before we store the character inour buffer, we check if it’s full or not. If so, we just clear the buffer and continue.Why are we doing this? URC’s are short messages with a length of about 7 to

5. Code implementation 20

15 characters and therefore predictable and an overflow should never happen.If it happens, then an overflow is avoided. Every URC message ends with the<s3 character>and until we haven’t received this we leave the ISR. After wereceived it we stop the timer, clear the GSM URC flag and unblock the GSMtask by setting the GSM URC event flag.

Important note: If the cellular module is in data mode, all sent charactersfrom the remote host are directly forwarded to the serial interface. This means,these characters are considered to belong to an URC and need to be handled inthe URC handler of the GSM task. The maximal length of data which can bereceived, depends on the buffer size. If this limit is exceeded, then the buffer issilently cleared, as mentioned above. Every message sent from a remote host tothe cellular module, needs to end with the <s3 character>, otherwise the parserwon’t be able to recognize a finished message.

Command

Every issued AT command has by default an echo which is sent first, followed bythe optional ITR and ends with the FRC. Therefore, we compare the receivedcharacter with our corresponding command character. It’s the same procedureas with the greeting text. If one character doesn’t match, we raise an error andunblock the GSM task. If it’s not finished, we wait for the next character. If it fin-ishes successfully, we set the GSM ECHO flag and the GSM FIRST AFTER ECHOflag in the PARSER register. The GSM FIRST AFTER ECHO flag is used toset the switch statement to its initial state. After the echo we check if the bufferis full or not. If it’s full, we set the error and unblock the GSM task with theGSM ERROR flag. To avoid such an overflow, one needs to adjust the buffersize to the largest possible output of the used AT commands. But for the sakeof completeness, the overflow is handled. In the normal case, when it is not fullwe store the character in the buffer.

The next state is more complicated as the possible answers of the cellularmodule are quite different. Normally, the response is composed of an ITR fol-lowed by a FRC or the response contains only a FRC. But if the cellular moduleresponses an error then the ITR and FRC are dropped and only the error issent. There is also a special case where only an ITR is sent without any FRC’s.This happens when the module changes from command mode to data mode byissuing a ”CONNECT”. This would not be a problem but ”CONNECT” is sendin verbose format and therefore with full header and footer:

<s3_character><s4_character> CONNECT <s3_character><s4_character>.

Finally, there are also responses which have more than one ITR line. Means, the<s3 character>is sent multiple times inside the ITR instead of only one time atthe end.

5. Code implementation 21

All these cases need to be handled correctly and in order to this a switchstatement is used. The first state which is entered is always the “wait fors3 character”. As long as this character hasn’t been received, we leave the ISR.After reception, we know that one part is fully received. This can either be aFRC, an error, an entire ITR or one part of a multiline ITR. If the receivedresponse matches one of the possible errors, then we raise an error and unblockthe GSM task by setting the GSM ERROR flag. If the expected response sim-ply consists of an FRC, we read out the value and unblock the GSM task bysetting the GSM COMMAND event flag. To signal that the AT command isfinished and URC’s are accepted again we clear the GSM COMMAND flag inthe PARSER register. The FRC value is stored in the GSM struct in the ”fi-nal result” parameter. If we expect an ITR, we change the state to ITR. Asmentioned in chapter 4.2 the ITR ends with <s3 character><s4 character>,therefore we need to wait for the s4 character to be received. This should be theconsecutive character of the s3 character. If the expected response is the specialcase ”CONNECT”, as mentioned above, we simply stay in the ITR state andwait for the next s4 character to be received. If it is not a special case, then wechange the state to FRC. Here we wait again until the s3 character is receivedas the FRC ends with this character. After reception, we check how long theresponse is. The maximal length of an FRC is three. If it’s longer than three,we have an ITR with multiple lines and therefore we change the state back toITR. If the length is within the accepted boundaries, we read out the value,unblock the GSM task by setting the GSM COMMAND event flag and clear theGSM COMMAND PARSER register flag.

5.4.4 GSM task

In this chapter, we consider the used FreeRTOS task called GSM task. Thegoal of this task is to establish an TCP/IP connection to the PermaSense databackend system, sending all pending data, listen if someone is sending anythinghe has to react to, tear down the connection and shut down the cellular module.

This task is thought to be used in the following manner: After a certain timeperiod, another task calls GSM powerOn(), leading the GSM task to enter theready state. The GSM task then performs all the steps mentioned in the goal ofthis task. After he has done everything, he enters the blocking state and waitsuntil he is set in ready state again.

Figure 5.3 shows the GSM task flow graph. If the cellular module (called GSM)is not running, the task enters the block state and waits to be unblocked by theevent flag GSM RUNNING. If it’s running, then we check if the greeting text hasalready been received or not. If not, we block and wait for the GSM GREETINGevent flag to be received. If the flag hasn’t been received within a certain time,the task is unblocked due to a timeout and we enter the error handler which

5. Code implementation 22

RTOS GSM-Task

GSM Running?

Greeting text already received?

Enter block state untill GSM is running

Enter block state until greeting text is

received or timeout

Enter block state until URC, ERROR or

TIMEOUT occurs

URC Handler Command Handler

ERROR Handler

No

Yes

Yes

No

Timeout

URC

Error

Timeout

Figure 5.3: GSM task

then needs to take a decision what to do. For now, we restart the module. Ifthe task is unblocked by the GSM GREETING event flag, we continue. Accord-ing to the AT command manual, one should wait at least 20ms before issuinga new AT command. Therefore, we enter the blocking state for at least 20msand wait if an URC or an error is responded by the parser. If the GSM ERRORevent flag unblocks the task we enter the error handler. If we are unblocked bya GSM URC event flag, we enter the URC handler instead. If a timeout occurs,then nothing is pending, and we can continue sending AT commands.

In the following the three used handlers will be introduced:

Error handler

All errors are stored in the GSM struct. The variable Error type holds the in-formation about the kind of error (UART error, Parser error or GSM error)which has occurred and the variable Error code contains more precise informa-tion about it. All errors need to be handled and this is thought to be done inthe error handler. For instance, one can log the error and then continue or resetthe parser and restart or one can just ignore the error. What is done is stronglydepending on the already existing error handling in the WGPS device code.

5. Code implementation 23

URC handler

If an URC has been received, this handler is entered. The URC message is storedin the aRxURCBuffer. The GSM struct contains a pointer on this buffer andstores its length. A possible URC is for instance

+CREG: 1

First, one needs to decide which URC’s has been received. The URC handlerchecks the length of the URC to already exclude URC’s with the wrong length.Then, we compare all possible URC’s with the received one and if we find theright one, we read out the value and decide what action needs to be done.

The URC handler is also entered if the cellular module is in data mode and theserver sends data to the module. This can be a command or similar. Note thateverything sent to the module needs to end with the <s3 character>, otherwisethe parser will fail to detect the end of the message.

Command handler

Switch stateEnter

GSM_SendAtCommand()function

Fill AtCommand struct with command name,

size, type, error type and response time

Error

Command Handler

Set GSM_COMMAND flag

Transmit AT command to cellular module

Enter blocked state until GSM_COMMAND,

GSM_ERROR event flags or timeout

GSM_COMMAND

Increment switch statestate += 1

ERROR Handler

Exit Command Handler

Timeout

Figure 5.4: Command handler flow graph

In the GSM CommandHandler() all AT commands are send and handled. To beable to leave the function after a finished command and to guarantee that URC’sare handled in time we use a struct statement. This allows us to jump to thecommand we want to send. Up to now the switch is split into six sections (Ini-tialization, Cellular network registration, Internal PDP context activation, Dataconnection, Data mode, Close data connection and End). The initialization isused to enable the numeric error response such that more precise error responsesare send by the module. The cellular network registration, the internal PDPcontext activation and the data connection are explained in a separate section,see chapter 5.5. In the data mode we send our data to the remote host we haveestablished a connection with. If we have send and received everything we needto enter the close data connection part, where we exit the direct link mode and

5. Code implementation 24

close the used socket. Entering the ”End” state turns off the cellular moduleand the UART interface.

To send an AT command we use the GSM SendAtCommand() function whichtakes the command name, it’s size, type, error type and maximal response time asinput. These parameters can differ between AT commands. In the function thesevalues are stored in the AtCommand struct and we set the GSM COMMANDflag to indicate that a response is expected. Next, we use the HAL driver functionHAL UART Transmit() to send the command to the cellular module. If this wassuccessful we enter the block state and wait to be unblocked. This can be throughthe GSM ERROR event flag, the GSM COMMAND event flag or by a timeout.If we get a timeout or an error, we enter the error handler, else we increment theswitch state and leave the function. The switch state can be set or read with theGSM CommandHandlerState() function.

5.5 Datalink

In this part, we derive a solution how we can establish a reliable datalink betweencellular module and a remote host. To test the datalink, YAT has been used asdummy remote host. YAT is a terminal which can listen and send data to adefined port and therefore acts as a simple server.

There are two possible ways how the cellular module could be used on thewireless GPS rev2 sensor system. Either it’s always on or its duty cycled. Ob-viously, duty cycling will be much more energy efficient. The problem is thereachability. The server won’t be able to send commands to the wireless GPSsensor system if the cellular module is in sleep mode or turned off. How doesthe server know when to send commands if needed? One possible solution isthat after the cellular module established a connection it sends all data and thensends a special preamble to indicate that it now waits a certain time to receivecommands from the server. The server can now send any commands it wantsto. After a certain command or time, the cellular module disconnects and turnsoff. This way it’s like a receiver indicated communication between server andcellular module.

What can be done if its’ kept always on? The nice way would be if the servercould establish a TCP/IP connection with the cellular module. The problemis that normally the network operator allows connectivity only in one direction.Means, only the module can establish a TCP/IP connection not the other wayaround. If there are special contracts or the possibility at all providing bothdirection hasn’t been investigated due to lack of time. A possible solution is thatthe module uses its keep alive mode which keeps the TCP connection open suchthat both can send any time they want. Disadvantage is that the server hasoccupied sockets and the module wastes lot of energy to keep it open. Another

5. Code implementation 25

way could be to call the module or send a SMS to it to inform that it shouldestablish a connection to the server.

5.5.1 GPRS system architecture overview

Before we talk about establishing a TCP/IP connection we first need to under-stand how the mobile network works and what is different to the normal IP basedinternet. Figure 5.5 gives an overview of the mobile network which is interposedbetween the cellular module and the IP based internet network.

Cellular module

BTS

MSC/VLR

BSC

SMS-MSC

HLR/AuC

EIR

BG

GGSN

GPRS NETWORK

FW

GPRSbackbone

SGSN

Other GPRSoperators

PLMN

ISDN

PSTN

SS7network

Data NetworkInternet

Data NetworkX.25

FW

FW

Figure 5.5: GSM and GPRS system architecture [18]

The cellular module needs to connect to a Base Transceiver Station (BTS).The BTS forwards the received signals to the Base Station Controller (BSC).Depending if the received signal is circuit switched traffic or packet switcheddata the BSC forwards it to the Mobile Switching Center (MSC) respectivelythe Serving GPRS Support Node (SGSN). The BSC is responsible for setting upand disconnecting Circuit Switched (CS) and Packet Switched (PS) connectionsto MSC respectively SGSN. The SGSN handles the packet data protocol (PDP)contexts. The GPRS backbone is now connected to other GPRS operators orvia a Gateway GPRS Support Node (GGSN) to an external data network. Forinstance, the IP based internet data network. The GGSN assigns IP addressesto mobile devices as the cellular module. This allows now to communicate overthe internet and to establish a TCP/IP connection.

5.5.2 Cellular network registration

This section provides an overview about the GSM/UMTS network registrationon the cellular module. First, we need to decide which Radio Access technology(RAT) we want to use. This can either be GSM, UMTS or GSM/UMTS in

5. Code implementation 26

dual mode. By default, it’s in dual mode and we let it like this as it switchesautomatically between the best available. Next, we can choose which operatingbands we want to use (800, 900, 1900, 2100 MHz etc.). The cellular modulecan store the network settings in its non-volatile memory (NVM) and thereforeonly needs to be changed once. The module is able to perform the networkregistration automatically based on the stored settings. Automatic registrationis enabled if the command “AT+COPS=0” is send. The automatic registrationis stored in the NVM. If the module is registered in GSM either GPRS or EDGEis available depending on the signal quality. If in UMTS then WCDMA, HSDPA,HSUPA or HSDPA/HSUPA can be available.

In our implementation we have the automatic registration enabled. There-fore, if the module is switched on it tries to establish a network registrationeither in GSM or in UMTS mode. If both are available, UMTS is preferred. Weenable the “+CREG” URC which informs us if the registration was successful.If we have received the corresponding URC, we continue with the Internal PDPcontext activation. Figure 5.6 shows how the network registration should beperformed and how the +CREG URC’s need to be handled.

Module.power.on

AT)CREG=g

AT)COPS?

Is.COPS≠h

NOYES

AT)COPS=Kor

AT)COPS=gyccc

Wait.for.URC)CREG

Read.)CREG

Is.)CREG=K DTE.is.requested.tointervene

YES

qgv.Everytime.a.URC)CREG.is.receivedytake.a.decision

Is.)CREG=gOKymodule.is.registered

for.CS.on.the.HPLMN

YES

NO

Is.)CREG=h Waity.module.issearching.for.a.network

YES

Is.)CREG=H

Registration.deniedc

Intervention.may.be

required

YES

NO

Is.)CREG=L WaitYES

Is.)CREG=3OKymodule.is.registred

for.CS.on.a.VPLMN

YES

NO

qgv

NO

NO

Figure 5.6: CS and PS network registration flow chart [17]

5. Code implementation 27

5.5.3 Internal PDP context activation

Before we can use TCP/IP we need to create a packet switched data (PSD)profile. This profile is used to set PDP context parameters for an internal context.This is, the protocol type (IPv4, IPv6), the APN together with username andpassword, the DNS address, the authentication, the IP address (dynamic, static)and the Quality of Service parameters (precedence, delay, reliability, peak rate,mean rate, delivery order, etc.). The profile can be stored in the NVM. Onceconfigured one can activate the PDP context with the specified profile.

In our implementation we first register the cellular module to the generalpacket radio service (GPRS). GPRS allows 2G and 3G networks to transmit IPpackets to networks such as the internet. Next, we load our PSD profile andactivate the PDP context. After the activation we have an IP address assignedto our module.

5.5.4 Data connection

In order to transfer data reliable, we use TCP/IP. Therefore, we create a socketon the cellular module. For the next step we need the IP address and the portfrom the remote host we want to connect to. We can do that with a DNSlookup or we hardcode the IP address and the port. As we used YAT as dummyserver to test the connection we hardcoded the IP and the port and establishedthe connection. If the connection is successful we get an OK as response. Inthe next step we enter the direct link mode. This pushes the module in datamode (see chapter 4.2.1). After “CONNECT” is received everything send to themodule is forwarded to the server. If we want to close the connection, we send+++ to exit the data mode and then we close the socket. Figure 5.7 shows howthe cellular module boots and establishes a TCP/IP connection with YAT.

5. Code implementation 28

============= START ============= Cellular Module Running - AT command: AT+CGMM Response: SARA-U270 0 - - AT command: AT+CGMI Response: u-blox 0 - - AT command: AT+CMEE=1 Response: 0 - - AT command: AT+CREG=1 Response: 0 - - AT command: AT+CREG? Response: +CREG: 1,0 0 - URC: +CREG: 1 - AT command: AT+CREG? Response: +CREG: 1,1 0 - - AT command: AT+COPS? Response: +COPS: 0,0,"Swisscom",0 0 -

- AT command: AT+UREG? Response: +UREG: 0,2 0 - - AT command: AT+URAT? Response: +URAT: 1,2 0 - - AT command: AT+CGATT? Response: +CGATT: 1 0 - - AT command: AT+UPSND=0,8 Response: +UPSND: 0,8,0 0 - - AT command: AT+UPSDA=0,2 Response: 0 - - AT command: AT+UPSDA=0,3 Response: 0 - - AT command: AT+UPSND=0,8 Response: +UPSND: 0,8,1 0 - - AT command: AT+UPSND=0,0 Response: +UPSND: 0,0,"10.185.2.127" 0 -

- AT command: AT+USOCR=6 Response: +USOCR: 0 0 - - AT command: AT+USOCO=0,"82.130.102.220",10000 Response: 0 - - AT command: AT+USODL=0 Response: CONNECT - URC: COMMAND FROM REMOTE HOST - AT command: +++ Response: - URC: 0 - AT command: AT+USOCL=0 Response: 0 - --------------------- Cellular Module OFF ---------------------

Figure 5.7: Boot, network registration, PDP context activation, socket creationand connection

Chapter 6

Further work

In this chapter we will briefly summarize what has been done and what hasn’t,as well as hints how to proceed with this work.

6.1 Achieved goals

The software interface between cellular module and MCU has been implemented.The interface is able to transmit all kind of AT commands and to react to thenecessary requirements. It is able to detect URC’s and provides an interfacewhich allows an easy handling of them. The interface is also able to detect datatransmitted by the remote host. Up to now there are no action taken if suchdata is received. The interface just outputs the received message and continues.All kind of errors are caught and are forwarded to an error handler. This errorhandler takes decisions how to handle the specific error.

As the goal was to implement and to include the interface in the already ex-isting WGPS software we only managed to implement the interface. It’s notincluded yet although everything is prepared such that the integration is thenext logical step.

6.2 Follow-up

According to the objectives, this work is designed in a way that follow-up projectscan be built upon. Therefore, special care has been taken such that everythingis implemented in a structured and generic way so that modification can be doneas simply as possible.

29

6. Further work 30

Defines

The code uses no hard-coded values for AT command settings which can bechanged. All of these values are mapped with defines. Therefore, if one changesfor instance, the s3 character, the only thing needed to adapt to is the corre-sponding define. All defines are located in the header file “gsm.h”.

TODO’s

If one wants to integrate the provided code into the wireless GPS sensor systemcode, there are several places where one needs to adapt the code. For sake ofsimplicity, the TODO’s mark these places. Every TODO contains also a shorttext which explains what is thought to be adapted.

README’s

The repository on Gitlab contains README’s which explains what needs to bedone in more details.

Code comments

The code contains comments everywhere where it could cause understandingproblems.

Inclusion into the wireless GPS rev2 sensor system code

This part will give a short summary of what needs to be done in order to integratethe code into the GPS sensor system code. The code is already implementedwith FreeRTOS. The most difficult part will be to adjust the interrupt and taskpriority so that it harmonizes with the other interrupts and tasks. Then, oneneeds to select the appropriate clock source for the USART2.

As the wireless GPS sensor system can enter the sleep mode, one needs toconsider that some variables may need to be volatile such that the value is storedbefore entering sleep mode. Next, one needs to define how the data is providedto the task and how it needs to be sent such that the PermaSense data backendsystem is able to process the data.

Chapter 7

Conclusion

In this work we proposed an integration concept which allows efficient commu-nication with the cellular module. Also, we proposed an efficient monitoringbased on the FreeRTOS task which allows us to monitor unsolicited result codes(URC’s), all kind of errors and the result of sent AT commands. Although nevertested with the PermaSense data backend system itself, we were able to establisha reliable TCP/IP connection with a dummy server, hosted on a computer andto exchange data in both directions. As this work is thought to be continued, theentire code is designed in a manner that follow-up projects can be easily buildupon. Comments and TODO’s help to understand what needs to be done andhow the code should be understood. No hard-coded values are used for valueswhich can be changed on the cellular module. Defines are used instead, to applythe changes globally.

The proposed code is completely embedded in the ARM/FreeRTOS softwareframework and has been developed and tested on the wireless GPS rev2 sensorsystem. Therefore, the integration in the already existing wireless GPS rev2sensor system code is straight forward.

31

Bibliography

[1] Atollic TrueStudio, http://www.st.com/en/development-tools/

truestudio.html

[2] STM32L496VG microcontroller, http://www.st.com/en/

microcontrollers/stm32l496vg.html

[3] SEGGER J-Link EDU, https://www.segger.com/products/

debug-probes/j-link/models/j-link-edu/

[4] U-blox SARA-U270 GSM Module,https://www.u-blox.com/de/product/sara-u2-series

[5] ITU-T Recommendation V24, 02-2000. List of definitions for interchangecircuits between Data Terminal Equipment (DTE) and Data ConnectionEquipment (DCE)

[6] u-blox Cellular Modules, Data and Voice Modules, AT Commands Manual,Document number: UBX-13002752, Revision R56, 22-Nov-2017

[7] SARA-U2 series, HSPA modules with 2G fallback, Data Sheet. Documentnumber: UBX-13005287, Revision R19, 26-Feb-2018

[8] STM32L496xx Datasheet. Document number: DS11585, Revision 8, May2018

[9] STM32L496 Refrence Manual. Document number: RM0351, Revision 6,April 2018

[10] Description of STM32L4/L4+ HAL and low-layer drivers. User manual.Document number: UM1884, Revision 7, September 2017

[11] Mastering the FreeRTOS Real Time Kernel, A Hands-On Tutorial Guide.Richard Barry, 2016

[12] The FreeRTOS Refrence Manual, API Functions and Configuration Op-tions. Version 10. Amazon Web Services, 2017

[13] Shockfish SA. Tinynode 184. http://www.tinynode.com/?q=product/tinynode184/tn-184-868

[14] Functional Specification of the next-gen WGPS device, wgps rev2 fs.pdf.Akos Pasztor, ETH Zurich TIK, 2016

32

Bibliography 33

[15] https://www.freertos.org/RTOS-task-states.html, online, 08.06.2018

[16] https://www.freertos.org/a00110.html, online, 08.06.2018

[17] AT Commands Examples, Examples for u-blox cellular modules, Applica-tion Note. Document number: UBX-13001820, Revision R11, 22-Sep-2016

[18] http://www.telecom.tuc.gr/~perak/speech/DSR-issues/

report-html/, online, 10.06.2018

[19] PermaSense Data Management: System documentation and tutorial for on-line data access. Samuel Weber, Jan Beutel, Christoph Walser, 2014

List of Figures

3.1 PermaSense System Architecture [19] . . . . . . . . . . . . . . . . 3

3.2 WGPS System overview [14] . . . . . . . . . . . . . . . . . . . . . 4

3.3 WGPS operating modes [14] . . . . . . . . . . . . . . . . . . . . . 5

3.4 Example interrupt priority configuration [16] . . . . . . . . . . . 6

4.1 SARA-U270 block diagram [7] . . . . . . . . . . . . . . . . . . . . 7

4.2 AT command response flow chart [17] . . . . . . . . . . . . . . . 9

4.3 URC flow chart [17] . . . . . . . . . . . . . . . . . . . . . . . . . 12

5.1 Valid task state transitions [15] . . . . . . . . . . . . . . . . . . . 14

5.2 AT command parser . . . . . . . . . . . . . . . . . . . . . . . . . 18

5.3 GSM task . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5.4 Command handler flow graph . . . . . . . . . . . . . . . . . . . . 23

5.5 GSM and GPRS system architecture [18] . . . . . . . . . . . . . 25

5.6 CS and PS network registration flow chart [17] . . . . . . . . . . 26

5.7 Boot, network registration, PDP context activation, socket cre-ation and connection . . . . . . . . . . . . . . . . . . . . . . . . . 28

34

Appendix A

WGPS Schematics

1

Proj

ect:

Perm

asen

se W

irele

ss G

PS 2

.0

File

:

Dat

e:

Dra

win

g nu

mbe

r:W

GPS

-REV

2

13.1

0.20

17

C:\U

sers

\ako

s\D

ocum

ents

\Per

mas

ense

\eng

inee

ring\

pcb\

proj

ects

\001

7_w

irele

ss_g

ps_r

ev2\

SCH

-Con

nect

ivity

.Sch

Doc

15:1

7:37

Form

at:

A4 Q

1.05

Rev

:

Dra

wn

by:

Labo

rato

ry:

ETH

TIK

Page

of1

7

Shee

t:

Akos

Pas

ztor

SCH

-Con

nect

ivity

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Doc

12

34

12

34

A B C D

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0 PIS409

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PIS1

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5 PIS

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7 PIS

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PIS1

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PIS1

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06

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PIS208

PIS209

PIS2

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PIS2

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PIS2

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PIS2

014

PIS2

015

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6 PI

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8 PI

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PIS2

020

PIS2

021

PIS2

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PIS3

03

PIS3

04

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PIS3

06

PIS3

07

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08

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03

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04

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PIS4

06

PIS4

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PIS4

08

PIS5

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01

PIS3

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PIS1

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PIS201

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02

PIS203

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04

Proj

ect:

Perm

asen

se W

irele

ss G

PS 2

.0

File

:

Dat

e:

Dra

win

g nu

mbe

r:W

GPS

-REV

2

13.1

0.20

17

C:\U

sers

\ako

s\D

ocum

ents

\Per

mas

ense

\eng

inee

ring\

pcb\

proj

ects

\001

7_w

irele

ss_g

ps_r

ev2\

SCH

-MC

U.S

chD

oc

15:1

7:37

Form

at:

A4 Q

1.05

Rev

:

Dra

wn

by:

Labo

rato

ry:

ETH

TIK

Page

of2

7

Shee

t:

Akos

Pas

ztor

SCH

-MC

U.S

chD

oc

12

34

12

34

A B C D

A B C D

P3V

GPS

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GPS

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PS_T

puls

e

The

GSM

mod

ule

has d

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inou

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UA

RT.

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d u-

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PA3

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PA4

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PA5

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PA6

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PA7

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PA8

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PA9

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PB10

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PB11

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PB12

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PB13

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PB14

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PB15

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PB2

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PB5

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PB6

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PB7

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PB8

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PC12

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PC3

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PC4

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PC5

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PC6

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PC7

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PC8

65

PC9

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PD0

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PD1

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PD10

57

PD11

58

PD12

59

PD13

60

PD14

61

PD15

62

PD2

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PD3

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PD4

85

PD5

86

PD6

87

PD7

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PD8

55

PD9

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PE0

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PE1

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PE10

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PE11

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PE12

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PE13

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PE14

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PE15

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PE2

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PIC301

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PI

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COC4

PIC501

PIC502

COC5

PIC601 PIC602 COC

6 PIC701 PIC702

COC7

PIC801 PIC802 COC

8 PIC901 PIC902

COC9

PIC1001 PIC1002 CO

C10

PIC1101 PIC1102 COC

11

PIC1301 PIC1302 COC

13

PIC1401 PIC1402 CO

C14

PIC1601 PIC1602 CO

C16

PIC7

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PIC7

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PIC7601 PIC7602 CO

C76

PID1

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PID1

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COD1

PID2

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PID2

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COD2

PID3

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PID3

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COD3

PIJ401

PIJ402

PIJ403

PIJ404

PIJ405

PIJ406

PIJ407

PIJ408

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PIQ102 PIQ103 COQ

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PIQ401

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PIR201 PIR202 COR2

PIR301 PIR302 COR3

PIR4

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PIR2401 PIR2402 COR24

PIR2501 PIR2502 COR25 PIR2601 PIR2602 CO

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27 PIR2801 PIR2802 COR28

PIRA

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PIRA

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PIRA

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PIRA

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PIS701

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PIS7

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PIU1057

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PIU1061

PIU1062

PIU1063

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PIU1

041

POSW0GSM

PIU1042

PODetect0GSM

PIU1043

PIU1044

POTN0EVREF

PIU1

045

POTN

0GPI

O PI

U104

6 POTN0BOLT0IND

PIU1

047

PIU1048

PIU1051 POTN0BOLT0REQ

PIU1052 POTN0SPI0SCK

PIU1

053 POTN0SPI0MISO

PIU1

054 POTN0SPI0MOSI

PIU1055

PIU1056 PO

Comp

ass0

XL0I

RQ

PIU1057 PO

Comp

ass0

MAG0

IRQ

PIU1060

PIU1062 POPWR0STAT

PIU1063

PIU1

064

PIU1067

PIU1

069

PIU1

077

PIU1082

PIU1084 POTN0BOLT0MODE

PIU1085 POTN0BOLT0ACK

PIU1086

PIU1087

PIU1

088

PIU1090 PO\SW0GPS

PIU1

091 POGPS0Tpulse

PIU1092 POGPS0Rx

PIU1093 PO

GPS0

Tx

PIU1098

PIU2

03

PIU304

PIC2

02

PIU108

PIY201 NL

OSC3

20IN

PIC4

02

PIU109

PIY202 NLOSC320OUT

PIC602 PIC702

PIC802 PIC902

PIC1002 PIC1102

PIC1402

PIC1602

PIQ404

PIR102 PIR202

PIR4

01

PIS7

04

PIU106

PIU1011

PIU1021

PIU1022

PIU1

028

PIU1

050

PIU1073

PIU1075

PIU1

0100

PIU205

PIU2

06

PIU4

01

PIC1302 PIJ404

PIQ401

PIQ402

PIQ405

PIQ406

PIR2402 PIR2502

PIR2602 PIR2702

PIR2802

NLP3

V0US

D

PIC102

PIU1

068

PIU305

NLP5V0USB

PIJ405

PIU1

080

NLSD

0CLK

PIJ403

PIR2401

PIU1

083

NLSD

0CMD

PIJ407

PIR2501

PIU1065

NLSD0D0

PIJ408

PIR2601

PIU1066

NLSD0D1

PIJ401

PIR2701

PIU1078

NLSD0D2

PIJ402

PIR2801

PIU1079

NLSD0D3

PIJ409

PIU1061

NLSD0Detect

PIC7

402

PIQ403 PIR402

PIU1081 NL

SW0U

SD

PIS701

PIU1

076

NLSW

CLK

PIS706

PIU1072

NLSWDIO

PIS7

02

PIU1089 NL

SWO

PIU1070

PIU302

NLUS

B0DM

POUSB0DM

PIU1071

PIU301 NL

USB0

DP

POUS

B0DP

PO\RESET

PO\SW0GPS

PO\S

W0Ti

lt

POCo

mpas

s0MA

G0CS

POCo

mpas

s0MA

G0IR

Q

POCo

mpas

s0XL

0CS

POCo

mpas

s0XL

0IRQ

PODetect0GSM

POGPS0Rx

POGPS0Tpulse

POGP

S0Tx

POGSM0CTS

POGSM0DCD

POGSM0DSR

POGSM0DTR

POGSM0RTS

POGSM0Rx

POGSM0Tx

POPWR0STAT

POSENSE03V

POSENSE0I

POSENSE0VBAT

POSW0GSM

POTilt0CS0X

POTi

lt0C

S0Y

POTilt0MISO

POTi

lt0M

OSI

POTilt0SCK

POTN0BOLT0ACK

POTN0BOLT0IND

POTN0BOLT0MODE

POTN0BOLT0REQ

POTN0EVREF

POTN

0GPI

O

POTN0SPI0MISO

POTN0SPI0MOSI

POTN0SPI0SCK

POUSB0DM

POUS

B0DP

Proj

ect:

Perm

asen

se W

irele

ss G

PS 2

.0

File

:

Dat

e:

Dra

win

g nu

mbe

r:W

GPS

-REV

2

13.1

0.20

17

C:\U

sers

\ako

s\D

ocum

ents

\Per

mas

ense

\eng

inee

ring\

pcb\

proj

ects

\001

7_w

irele

ss_g

ps_r

ev2\

SCH

-PW

R.S

chD

oc

15:1

7:37

Form

at:

A4 Q

1.05

Rev

:

Dra

wn

by:

Labo

rato

ry:

ETH

TIK

Page

of3

7

Shee

t:

Akos

Pas

ztor

SCH

-PW

R.S

chD

oc

12

34

12

34

A B C D

A B C D

P5V

_USB

STAT

1

D0

2

D1

3IL

IM4

GN

D

5

IN2

6O

UT

7IN

18

U7

TPS2

115A

PWPW

R_S

TAT

P3V

OU

T1

NR

/FB

3

GN

D

4

EN5

IN8

U9

TPS7

3530

QD

RB

220u

F6.

3V

C28

PV_I

N

PV_B

AT

PV_I

N

SEN

SE_I

SEN

SE_V

BA

T

Pow

er S

uppl

y

Cur

rent

Mea

sure

men

t of S

yste

m V

olta

geB

atte

ry In

put:

11V

- 20

V

Prot

ecte

d In

put f

rom

Bat

tery

USB

5V

Inpu

t

Inpu

t Sou

rce

Pow

er M

ultip

lexe

r

Vol

tage

Mea

sure

men

t of B

atte

ry

P3V

SEN

SE_3

V

Syst

em V

olta

ge M

easu

rem

ent

D4

SMC

J26A

D6

SMC

J12A

D5

SS24

F1 1.1A

F2 500m

A

GND 1

GND 2

OUT 3

RS-4 RS+5

U8

MA

X96

10H

EXK

+T

220u

F6.

3V

C61

35 V

C20

4.7u

F

50 V

C27

100n

FC

2910

nF

C17

10nF

1 %

R9

33K

2

1 %

R10

12K

1 %

R11

430R

1 %

R6

1M 1 %

R7

140K

R5

47k

L110

0uH

C68

6.8n

F

R20

287K

R23

40K

2

C70

11pF

C71

15nF

50 V

C67

100n

F

6.3

V

C69

47uF

10V

C26

220u

F

6.3V

C22

330u

F

6.3V

C21

330u

FC

2310

0nF

C24

100n

FC

2510

0nF

C18

1uF

25V

100u

F

C19

BOO

T1

VIN

2

EN3

SS/T

R4

RT/

CLK

5PW

RG

D6

VSEN

SE7

CO

MP

8G

ND

9

PH10

PP11

U6

TPS5

4040

DG

Q

0.25

W1%R

80.

15R

R15

100k

PIC1701 PIC1702 CO

C17

PIC1801 PIC1802 COC

18

PIC1901 PIC1902 CO

C19

PIC2001 PIC2002 COC

20

PIC2101 PIC2102

COC21

PIC2201 PIC2202

COC22

PIC2301 PIC2302 COC

23 PIC2401 PIC2402

COC24

PIC2501 PIC2502 COC

25

PIC2601 PIC2602

COC2

6

PIC2701 PIC2702 CO

C27

PIC280N PIC280P COC

28

PIC2901 PIC2902 COC

29

PIC610N PIC610P COC

61

PIC6

701

PIC6

702

COC67

PIC6

801

PIC6

802

COC68

PIC6901 PIC6902 COC

69

PIC7001 PIC7002 COC

70 PIC7101 PIC7102

COC71

PID401 PID402 COD

4

PID501 PID502 COD

5

PID601 PID602 COD

6

PIF1

01

PIF1

02

COF1

PIF201

PIF202

COF2

PIL1

01

PIL1

02

COL1

PIR501 PIR502 COR5

PIR601 PIR602 COR6

PIR701 PIR702 COR7

PIR8

01

PIR8

02

COR8

PIR901

PIR902 COR

9

PIR1001 PIR1002 COR10

PIR1101 PIR1102 COR11

PIR1

501

PIR1

502

COR15

PIR2

001

PIR2

002

COR20

PIR230

1 PIR

2302

COR23

PIU601

PIU602

PIU603

PIU604

PIU605

PIU606

PIU607

PIU608

PIU609

PIU6010

PIU6

011

COU6

PIU7

01

PIU702

PIU7

03

PIU704

PIU705

PIU7

06

PIU7

07

PIU7

08 COU

7

PIU801 PIU802

PIU803 PIU804 PIU805 COU

8

PIU901

PIU9

03

PIU904

PIU9

05

PIU908 COU

9

PIC1701 PIC1801

PIC1902 PIC2001

PIC2102

PIC2202

PIC2301 PIC2401

PIC2501

PIC2602 PIC2701

PIC280N PIC2901

PIC610N

PIC6

802

PIC6901

PIC7001 PIC7101

PID401

PID501

PID601

PIR701

PIR1001 PIR1101

PIR2

002

PIU609

PIU6

011

PIU702

PIU705

PIU801 PIU802

PIU904 PIU909

PIC1702 PIR601 PIR702

POSENSE0VBAT

PIC1802 PIR501 POSENSE03V

PIC2101 PIC2502

PIR8

01

PIU7

07

PIU805

PIC2201

PIC2402

PIC6902

PIL1

02

PIR901

PIU7

03

PIU7

08

PIC2302

PIC280P

PIU7

06

PIU901

PIC2601 PIC2702

PID602 PIF202

PIU9

05

PIU908

PIC2902 PI

U903

PIC6

701

PID502

PIL1

01

PIU6010 PI

C670

2 PIU601

PIC6

801

PIU604

PIC7002 PIR230

2

PIC7102 PIR

2301

PIU608

PIR902

PIR1002

PIU607

PIR1102 PIU704

PIR1

501

PIU603

PIR2

001

PIU605

PIU606

PIU7

01 POPWR0STAT

PIU803 PO

SENS

E0I

PIC610P

PIR502 PI

R802

PIU804

PIF201

PIF1

01

PIC1901 PIC2002

PID402

PIF1

02

PIR602 PIR1

502

PIU602

POPWR0STAT

POSENSE03V

POSE

NSE0

I

POSENSE0VBAT

Proj

ect:

Perm

asen

se W

irele

ss G

PS 2

.0

File

:

Dat

e:

Dra

win

g nu

mbe

r:W

GPS

-REV

2

13.1

0.20

17

C:\U

sers

\ako

s\D

ocum

ents

\Per

mas

ense

\eng

inee

ring\

pcb\

proj

ects

\001

7_w

irele

ss_g

ps_r

ev2\

SCH

-GPS

.Sch

Doc

15:1

7:37

Form

at:

A4 Q

1.05

Rev

:

Dra

wn

by:

Labo

rato

ry:

ETH

TIK

Page

of4

7

Shee

t:

Akos

Pas

ztor

SCH

-GPS

.Sch

Doc

12

34

12

34

A B C D

A B C D

NC

1

NC

2

TxD

3

RxD

4

D_S

EL5

VCC

6 7

VCC

_OU

T8

NC

9

RES

ET10

V_BC

KP

11

Tim

epul

se2

12

13GN

D1415

RF_

IN16

17

VCC

_RF

18

V_AN

T19

ExtIn

t1/A

ADET

20

NC

21

NC

22

NC

23

VDD

_USB

24

USB

_DM

25

USB

_DP

26

ExtIn

t027

Tim

epul

se1

28

U10

LEA

-M8T

P3V

1 %

R13

10R

GPS

_Tpu

lse

GPS

_Rx

GPS

_Tx

SW_G

PS

GPS

Mod

ule

S1

S8 SMA

GPS

& C

ompa

ss

P3V

E-C

ompa

ss 3

D a

ccel

erom

eter

& 3

D m

agne

tom

eter

Tilt_

MO

SI

Tilt_

SCK

Com

pass

_XL_

CS

Com

pass

_XL_

IRQ

GPS

VC

C:

Low

indu

ctan

ce &

resi

stan

ce,

accu

rate

, te

mpe

ratu

re-c

ompe

nsat

ing

caps

,1u

+ 1

00n

+ 1n

+ 1

0p

R12

100k

C34

10uF

C30

10pF

C0G

C31

1nF

C0G

C32

100n

F

Q2

FDC

638P

P3V

_GSM

_SW

Switc

habl

e 3V

Sup

ply

for G

PS

Supp

ly fo

r Ultr

a-Lo

w P

ower

E-C

ompa

ss is

not

nee

ded

to b

e sw

itcha

ble;

alw

ays O

N

iG

PS A

nten

na

SMA

Con

nect

or P

CB

Des

ign:

- stra

ight

rout

ing

- cop

per p

our c

lear

ance

: >16

mil

- wire

wid

th: >

30m

il- n

o po

ur o

n ro

utin

g la

yer u

nder

SM

A

SPL/

SPC

1

CS_

XL2

CS_

MAG

3

SDA/

SDI/S

DO

4C

15

GN

D

6

INT_

MAG

7

GN

D

8

VDD

9

VDD

_IO

10

DR

DY_

MAG

11

INT_

XL12

U11

LSM

303C

TR

Com

pass

_MA

G_I

RQ

Com

pass

_MA

G_C

S

220u

F6.

3V

C37

C35

100n

F

C36

100n

F

C33

1uF

P3V

C57

10nF

C65

100n

F

R30

0R

R31

0R

Not

fitte

d

PIC3001 PIC3002 CO

C30

PIC3101 PIC3102 COC

31

PIC3201 PIC3202 COC

32

PIC3301 PIC3302 CO

C33

PIC3401 PIC3402 COC

34 PIC3501 PIC3502

COC35

PIC3601 PIC3602 COC

36

PIC370N PIC370P CO

C37

PIC5701 PIC5702 CO

C57

PIC650

1 PIC

6502

COC65

PIQ201 PIQ202 PIQ203

PIQ204 PIQ205 PIQ206 COQ

2 PIR1201 PIR1202 COR

12

PIR1301 PIR1302

COR13

PIR3001 PIR3002

COR30

PIR3

101

PIR3

102 COR

31

PIS801

PIS802 PIS803 PIS804 PIS805 COS8

PIU1

001

PIU1

002

PIU1

003

PIU1

004

PIU1

005

PIU1006 PIU1007

PIU1

008

PIU100

9

PIU1

0010

PIU10011

PIU1

0012

PIU10013 PIU10014

PIU10015

PIU1

0016

PIU10017

PIU1

0018

PIU1

0019

PIU100

20 PIU

10021

PIU1

0022

PIU1

0023

PIU1

0024

PIU100

25 PI

U100

26

PIU1

0027

PIU1

0028

COU10

PIU1101

PIU1

102

PIU1103

PIU1104

PIU1105

PIU1106

PIU1107

PIU1108

PIU1109 PIU11010

PIU1

1011

PIU1

1012

COU11

PIC3001 PIC3101

PIC3201 PIC3301

PIC3401 PIC3501 PIC3601

PIC370N PIC5701

PIC650

1

PIS802 PIS803 PIS804 PIS805

PIU1007 PIU10013

PIU10014 PIU10015

PIU10017

PIU1

0024

PIU1106 PIU1108

PIC3602

PIU1105

PIC5702

PIQ203

PIR1201 PO\SW0GPS

PIC650

2

PIR3002

PIR3

101 PIU10011

PIR1301 PI

U100

18

PIR1302 PI

U100

19

PIS801

PIU1

0016

PIU1

001

PIU1

002

PIU1

003

POGPS0Tx

PIU1

004

POGPS0Rx

PIU1

005

PIU1

008

PIU100

9

PIU1

0010

PIU1

0012

PIU100

20 PIU

10021

PIU1

0022

PIU1

0023

PIU100

25 PI

U100

26

PIU1

0027

PIU1

0028

POGPS0Tpulse

PIU1101 POTilt0SCK

PIU1

102

POCompass0XL0CS

PIU1103 PO

Comp

ass0

MAG0

CS

PIU1104 POTilt0MOSI

PIU1107

POCompass0MAG0IRQ

PIU1

1011

PIU1

1012

PO

Comp

ass0

XL0I

RQ

PIC3402 PIC3502

PIC370P

PIQ204 PIR1202

PIR3001

PIU1109 PIU11010

PIC3002 PIC3102

PIC3202 PIC3302

PIQ201 PIQ202 PIQ205 PIQ206 PI

R310

2

PIU1006

NLP3V0

GSM0SW

PO\SW0GPS

POCo

mpas

s0MA

G0CS

POCompass0MAG0IRQ

POCompass0XL0CS

POCo

mpas

s0XL

0IRQ

POGPS0Rx

POGPS0Tpulse

POGPS0Tx

POTilt0MOSI

POTilt0SCK

Proj

ect:

Perm

asen

se W

irele

ss G

PS 2

.0

File

:

Dat

e:

Dra

win

g nu

mbe

r:W

GPS

-REV

2

13.1

0.20

17

C:\U

sers

\ako

s\D

ocum

ents

\Per

mas

ense

\eng

inee

ring\

pcb\

proj

ects

\001

7_w

irele

ss_g

ps_r

ev2\

SCH

-Tilt

.Sch

Doc

15:1

7:37

Form

at:

A4 Q

1.05

Rev

:

Dra

wn

by:

Labo

rato

ry:

ETH

TIK

Page

of5

7

Shee

t:

Akos

Pas

ztor

SCH

-Tilt.

SchD

oc

12

34

12

34

A B C D

A B C D

Tilt

Sen

sors

Tilt_

MIS

OTi

lt_M

OSI

Tilt_

CS_

XTi

lt_C

S_Y

Tilt_

SCK

P3V

_TIL

T

SW_T

ilt

FB1

BLM

18H

G10

2SN

1D

Rsv

d.1

Rsv

d.2

AVSS 3

AVD

D

4

CS

5

MIS

O6

SCK

7

MO

SI8

PWM

9D

VDD

10

DVS

S

11EGN

D12

U12

SCA

830

P3V

_TIL

T_SW

P3V

_TIL

T_SW

Rsv

d.1

Rsv

d.2

AVSS 3

AVD

D

4

CS

5

MIS

O6

SCK

7

MO

SI8

PWM

9D

VDD

10

DVS

S

11EGN

D12

U13

SCA

830

P3V

_TIL

T_SW

Plac

e Ti

lt Se

nsor

s with

90°

diff

eren

t alig

nmen

t

Tilt_

SCK

Tilt_

MIS

OTi

lt_M

OSI

Tilt_

CS_

X

Tilt_

SCK

Tilt_

MIS

OTi

lt_M

OSI

Tilt_

CS_

Y

Tilt_

SCK

Tilt_

MIS

OTi

lt_M

OSI

Tilt_

CS_

XTi

lt_C

S_Y

Tilt

Sen

sors

R14

100k

Q3

FDC

638P

Switc

habl

e 3V

Sup

ply

Vol

tage

for T

ilt S

enso

rs

3V re

ceiv

ed fr

om m

ain

PCB

via

con

nect

or

C39

100n

FC

4010

0nF

C41

100n

FC

4210

0nF

6.3

V

C72

47uF

P3V

Plac

e C

AP

near

con

nect

or

100u

C38

PIC3801 PIC3802 COC

38 PIC3901 PIC3902

COC39

PIC4001 PIC4002 COC

40 PIC4101 PIC4102

COC41

PIC4201 PIC4202 CO

C42

PIC7201 PIC7202 COC

72

PIFB10

1 PIF

B102

COFB1

PIQ301 PIQ302 PIQ303

PIQ304 PIQ305 PIQ306 COQ

3 PIR1401 PIR1402

COR1

4

PIU1

201

PIU120

2

PIU1203 PIU1204

PIU1

205

PIU1

206

PIU1

207

PIU120

8

PIU1

209

PIU12010 PIU12011

PIU1

2012

COU1

2

PIU1

301

PIU130

2

PIU1303 PIU1304

PIU1

305

PIU1

306

PIU1

307

PIU130

8

PIU1

309

PIU13010 PIU13011

PIU1

3012

COU1

3

PIC3801 PIC3901

PIC4001 PIC4101

PIC4201 PIC7201

PIU1

201

PIU120

2

PIU1203 PIU12011

PIU1

2012

PIU1

301

PIU130

2

PIU1303 PIU13011

PIU1

3012

PIFB10

1

PIQ301 PIQ302 PIQ305 PIQ306 PIQ303

PIR1401 PO

\SW0

Tilt

PIU1

209

PIU1

309

PIC7202

PIQ304 PIR1402

PIC3802 PIC3902

PIC4002 PIC4102

PIC4202

PIFB10

2

PIU1204 PIU12010

PIU1304 PIU13010

PIU1

205

NLTilt0CS0X

POTilt0CS0X

PIU1

305

NLTilt0CS0Y

POTilt0CS0Y

PIU1

206

PIU1

306

NLTilt0MISO

POTilt0MISO

PIU120

8 PIU

1308

NLTilt0MOSI

POTilt0MOSI

PIU1

207

PIU1

307

NLTi

lt0S

CK

POTi

lt0S

CK

PO\S

W0Ti

lt

POTilt0CS0X

POTilt0CS0Y

POTilt0MISO

POTilt0MOSI

POTi

lt0S

CK

Proj

ect:

Perm

asen

se W

irele

ss G

PS 2

.0

File

:

Dat

e:

Dra

win

g nu

mbe

r:W

GPS

-REV

2

13.1

0.20

17

C:\U

sers

\ako

s\D

ocum

ents

\Per

mas

ense

\eng

inee

ring\

pcb\

proj

ects

\001

7_w

irele

ss_g

ps_r

ev2\

SCH

-GSM

.Sch

Doc

15:1

7:37

Form

at:

A4 Q

1.05

Rev

:

Dra

wn

by:

Labo

rato

ry:

ETH

TIK

Page

of6

7

Shee

t:

Akos

Pas

ztor

SCH

-GSM

.Sch

Doc

12

34

12

34

A B C D

A B C D

DSR

6

RI

7

DC

D8

DTR

9

RTS

10

CTS

11

TXD

12

RXD

13

PWR

_ON

15

GPI

O1

16

VUSB

_DET

17

RES

ET_N

18

CO

DEC

_CLK

19

GPI

O2

23

GPI

O3

24

GPI

O4

25

SDA

26SC

L27

USB

_D-

28

USB

_D+

29

I2S_

WA

34

I2S_

TXD

35

I2S_

CLK

36I2

S_R

XD37

SIM

_CLK

38SI

M_I

O39

SIM

_RST

40

VSIM

41SI

M_D

ET42

ANT

56

ANT_

DET

62

U15

A

SAR

A-U

270-

00S

GN

D1

GN

D3

GN

D5

GN

D14

GN

D20

GN

D21

GN

D22

GN

D30

GN

D32

GN

D43

GN

D50

GN

D54

GN

D55

GN

D57

GN

D58

GN

D59

GN

D60

GN

D61

GN

D63

GN

D64

GN

D65

GN

D66

GN

D67

GN

D68

GN

D69

GN

D70

GN

D71

GN

D72

GN

D73

GN

D74

GN

D75

GN

D76

GN

D77

GN

D78

GN

D79

GN

D80

GN

D81

GN

D82

GN

D83

GN

D84

GN

D85

GN

D86

GN

D87

GN

D88

GN

D89

GN

D90

GN

D91

GN

D92

GN

D93

GN

D94

GN

D95

GN

D96

V_BC

KP2

V_IN

T4

RSV

D31

RSV

D33

RSV

D44

RSV

D45

RSV

D46

RSV

D47

RSV

D48

RSV

D49

VCC

51

VCC

52

VCC

53

U15

B

SAR

A-U

270-

00S

GSM

_Rx

GSM

_Tx

GSM

_RTS

GSM

_CTS

GSM

_DSR

GSM

_DTR

GSM

_DC

D

Leve

l-mat

chin

g: 3

V to

1V

8

P3V

8

BOO

ST1

VIN

2

VSW

3

4

SHD

N5

FB6

VC7

SYN

C8

GN

D

U14

LT17

65ES

8#PB

F

D7

SD10

3CW

S-7-

FP3

V8

PV_I

N_G

SM

SW_G

SM

GSM

Pow

er S

uppl

y

P1V

8

P1V

8

P1V

8

P3V

_GSM

P3V

_GSM

1%

RA

2

3k9

1%RA

35k

6

Leve

l-mat

chin

g: 1

V8

to 3

V

S1

S10

SMA

Cel

lula

r

Det

ect_

GSM

GSM

PC

B d

etec

tion

D8

SS24

L23.

3uH

Nea

r-C

hip

Cap

acito

rs

P3V

_GSM

P1V

8

R19

100k

C55

47pF

C58

47pF

C59

47pF

C47

56pF

C0G

C46

10nF

1 %

R16

33k

1 %

R18

15k

50 V

C43

180n

F

C50

2.2n

F

Shie

ld

VCC

C1

RST

C2

CLK

C3

GN

DC

5

VPP

C6

I/OC

7

Nano_SIM

J3 Nan

oSIM

-hol

der

Supp

ly V

olta

ge fr

om B

atte

ry re

ceiv

ed fr

om m

ain

PCB

via

con

nect

or

1V8

Vol

tage

is p

rodu

ced

by G

SM M

odul

e

SMA

Con

nect

or P

CB

Des

ign:

- stra

ight

rout

ing

- cop

per p

our c

lear

ance

: >16

mil

- wire

wid

th: >

30m

il- n

o po

ur o

n ro

utin

g la

yer u

nder

SM

A

iG

SM A

nten

na

GN

D4

B26

B17

DIR

5

A12

A23

VCC

A1

VCC

B8

U17

SN74

LVC

2T45

DC

UR

GN

D4

B26

B17

DIR

5

A12

A23

VCC

A1

VCC

B8

U16

SN74

LVC

2T45

DC

UR

6.3V

C44

470u

F6.

3V

C63

470u

FC

4810

pFC

0G

C45

100n

FC

5110

0nF

C52

100n

FC

5310

0nF

C54

100n

F

C60

100n

F

25V

100u

F

C49

25V

100u

F

C62

IN1

OU

T5

EN3

2

4

GN

D

U5

TPS7

8230

DD

CR

P3V

_GSM C

1210

uF

R17 4k

7

R32

100k

PIC1201 PIC1202 COC

12

PIC4301 PIC4302 CO

C43

PIC4401 PIC4402

COC4

4

PIC4501 PIC4502 COC

45 PIC4601 PIC4602

COC46

PIC4701 PIC4702 CO

C47

PIC4801 PIC4802 CO

C48

PIC4901 PIC4902 COC

49

PIC5001 PIC5002 CO

C50

PIC5101 PIC5102 COC

51 PIC5201 PIC5202

COC52

PIC5301 PIC5302 COC

53 PIC5401 PIC5402

COC54

PIC5501 PIC5502 COC

55 PIC5801 PIC5802

COC58

PIC5901 PIC5902 COC

59 PIC6001 PIC6002

COC60

PIC6201 PIC6202 COC

62 PIC6301 PIC6302

COC63

PID701

PID702 COD7

PID801 PID802 COD

8

PIJ30C1

PIJ3

0C2

PIJ30C3

PIJ3

0C5

PIJ3

0C6

PIJ30C7

PIJ3

0Shi

eld COJ

3

PIL201

PIL202

COL2

PIR1

601

PIR1

602

COR16

PIR1701 PIR1702 COR1

7

PIR1801 PIR1802 COR18

PIR1901 PIR1902 COR1

9

PIR3201 PIR3202 COR3

2

PIRA20

1 PIR

A202

PIRA

203

PIRA

204

PIRA

205

PIRA

206

PIRA

207

PIRA

208

CORA

2

PIRA301 PIRA302

PIRA303 PIRA304

PIRA305 PIRA306

PIRA307 PIRA308 CO

RA3

PIS1001

PIS1002 PIS1003 PIS1004 PIS1005

COS10

PIU501

PIU502 PIU503

PIU504

PIU505

COU5

PIU1401

PIU1402

PIU1

403

PIU1404

PIU1

405

PIU1406

PIU1407

PIU1408 COU1

4

PIU1506

PIU1507

PIU1

508

PIU1509

PIU1

5010

PI

U150

11

PIU1

5012

PIU1

5013

PIU1

5015

PIU1

5016

PIU1

5017

PIU1

5018

PIU1

5019

PIU1

5023

PI

U150

24

PIU1

5025

PIU1

5026

PIU1

5027

PIU1

5028

PIU1

5029

PIU1

5034

PIU1

5035

PIU1

5036

PIU1

5037

PIU1

5038

PIU1

5039

PIU1

5040

PIU1

5041

PIU1

5042

PIU1

5056

PIU1

5062

COU15A

PIU1501

PIU1

502

PIU1503

PIU1504

PIU1505

PIU1

5014

PI

U150

20

PIU1

5021

PIU1

5022

PIU1

5030

PIU1

5031

PIU1

5032

PIU1

5033

PIU1

5043

PIU1

5044

PIU1

5045

PIU1

5046

PIU1

5047

PIU1

5048

PI

U150

49

PIU1

5050

PIU1

5051

PIU1

5052

PIU1

5053

PIU1

5054

PIU1

5055

PIU1

5057

PI

U150

58

PIU1

5059

PIU1

5060

PIU1

5061

PIU1

5063

PI

U150

64

PIU1

5065

PIU1

5066

PIU1

5067

PI

U150

68

PIU1

5069

PIU1

5070

PIU1

5071

PIU1

5072

PIU1

5073

PI

U150

74

PIU1

5075

PIU1

5076

PIU1

5077

PIU1

5078

PI

U150

79

PIU1

5080

PIU1

5081

PIU1

5082

PIU1

5083

PI

U150

84

PIU1

5085

PIU1

5086

PIU1

5087

PIU1

5088

PI

U150

89

PIU1

5090

PIU1

5091

PIU1

5092

PI

U150

93

PIU1

5094

PIU1

5095

PIU1

5096

COU15B

PIU1

601

PIU1602

PIU1603

PIU1

604

PIU1605

PIU1606

PIU1607

PIU1

608 CO

U16

PIU1701

PIU1

702

PIU1

703

PIU1704

PIU1705

PIU1

706

PIU1

707

PIU1708 COU1

7

PIC1201 PIC4402

PIC4501 PIC4601

PIC4701 PIC4801

PIC4902 PIC5001

PIC5101 PIC5201

PIC5301 PIC5401

PIC5501 PIC5801

PIC5901 PIC6001

PIC6202 PIC6302

PID801

PIJ3

0C5

PIJ3

0Shi

eld

PIR1701

PIR1801 PIR3201

PIRA301 PIRA303

PIRA305

PIS1002 PIS1003 PIS1004 PIS1005

PIU502 PIU504

PIU1404

PIU1408

PIU1501

PIU1503

PIU1505

PIU1

5014

PI

U150

20

PIU1

5021

PIU1

5022

PIU1

5030

PIU1

5032

PIU1

5033

PIU1

5043

PI

U150

50

PIU1

5054

PIU1

5055

PIU1

5057

PI

U150

58

PIU1

5059

PIU1

5060

PIU1

5061

PIU1

5063

PI

U150

64

PIU1

5065

PIU1

5066

PIU1

5067

PI

U150

68

PIU1

5069

PIU1

5070

PIU1

5071

PIU1

5072

PIU1

5073

PI

U150

74

PIU1

5075

PIU1

5076

PIU1

5077

PIU1

5078

PI

U150

79

PIU1

5080

PIU1

5081

PIU1

5082

PIU1

5083

PI

U150

84

PIU1

5085

PIU1

5086

PIU1

5087

PIU1

5088

PI

U150

89

PIU1

5090

PIU1

5091

PIU1

5092

PI

U150

93

PIU1

5094

PIU1

5095

PIU1

5096

PIU1

604

PIU1605

PIU1704

PIU1705 PIC4301 PID802

PIL201

PIU1

403

PIC4302 PID702

PIU1401

PIC5002 PIU1407

PIC5502

PIJ3

0C2

PIU1

5040

PIC5802

PIJ30C3

PIU1

5038

PIC5902

PIJ30C7

PIU1

5039

PIC6002

PIJ30C1

PIU1

5041

PIJ3

0C6

PIR1

601

PIR1802 PIU1406

PIR1702 PODetect0GSM

PIR1901 PI

U150

15

PIR1902 PI

U150

2

PIR3202

PIU1

405

POSW0GSM

PIRA20

1 POGSM0Tx

PIRA20

2

PIRA306 PI

U150

12

PIRA

203

POGSM0RTS

PIRA

204

PIRA304 PI

U150

10

PIRA

205

POGS

M0DT

R PI

RA20

6

PIRA302

PIU1509

PIRA

207

PIRA

208

PIRA307 PIRA308

PIS1001

PIU1

5056

PIU1506

PIU1

707

PIU1507

PIU1

508

PIU1

706

PIU1

5011

PIU1606

PIU1

5013

PIU1607

PIU1

5016

PIU1

5017

PIU1

5018

PIU1

5019

PIU1

5023

PI

U150

24

PIU1

5025

PIU1

5026

PIU1

5027

PIU1

5028

PIU1

5029

PIU1

5031

PIU1

5034

PIU1

5035

PIU1

5036

PIU1

5037

PIU1

5042

PIU1

5044

PIU1

5045

PIU1

5046

PIU1

5047

PIU1

5048

PI

U150

49

PIU1

5062

PIU1602

POGSM0Rx

PIU1603

POGSM0CTS

PIU1

702

POGSM0DSR

PIU1

703

POGSM0DCD

PIC5302 PIC5402

PIU1504

PIU1

608

PIU1708

PIC4401 PIC4502

PIC4602 PIC4702

PIC4802 PIC6301

PID701

PIL202

PIR1

602

PIU501

PIU503

PIU1

5051

PIU1

5052

PIU1

5053

PIC1202 PIC5102

PIC5202

PIU505

PIU1

601

PIU1701

PIC4901 PIC6201

PIU1402

PODetect0GSM

POGSM0CTS

POGSM0DCD

POGSM0DSR

POGS

M0DT

R POGSM0RTS

POGSM0Rx

POGSM0Tx

POSW0GSM

Proj

ect:

Perm

asen

se W

irele

ss G

PS 2

.0

File

:

Dat

e:

Dra

win

g nu

mbe

r:W

GPS

-REV

2

13.1

0.20

17

C:\U

sers

\ako

s\D

ocum

ents

\Per

mas

ense

\eng

inee

ring\

pcb\

proj

ects

\001

7_w

irele

ss_g

ps_r

ev2\

SCH

-Tin

yNod

e.Sc

hDoc

15:1

7:37

Form

at:

A4 Q

1.05

Rev

:

Dra

wn

by:

Labo

rato

ry:

ETH

TIK

Page

of7

7

Shee

t:

Akos

Pas

ztor

SCH

-Tin

yNod

e.Sc

hDoc

12

34

12

34

A B C D

A B C D

1 2 3

S11

SIP-

3

Har

ting

0918

-514

-632

4

1 2 3 4 5 6 7 8 9 10 11 12 13 14

S13

SIP-

7x2

TDO

1VC

C2

TDI

3VR

eg4

TMS

5G

ND

6

TCK

7nR

ST8

UR

XD1

9nR

EGE

10

UTX

D11

P5.0

/STE

112

P1.2

/TA1

13P5

.1/S

IMO

114

P1.3

/TA2

15P5

.2/S

OM

I116

E_EV

REF

17P5

.3/U

CLK

118

P6.7

/AD

C7/

DAC

119

P1.6

/TA1

20

P6.6

/AD

C6/

DAC

021

P2.3

/CA0

/TA1

22

P6.5

/AD

C5

23P2

.4/C

A1/T

A224

P6.4

/AD

C4

25P4

.0/T

B026

P6.3

/AD

C3

27T4

.1/T

B128

P6.2

/AD

C2

29E_

IVR

EF30

Scre

w

J2Ti

nyN

ode1

84TN

_TD

O

TN_T

DI

TN_T

MS

TG_P

RO

G

P3V

VC

C_T

AR

GET

VC

C_T

OO

L

TG_R

ESET

TG_R

ESET

P3V

Nea

r-ch

ip c

apac

itors

for T

N &

per

iphe

ry

GN

D1

DQ

2

NC

3N

C5

NC

6N

C4

U18

DS2

401P

P3V

_TN

_PER

IPH

TN_S

PI_M

OSI

TN_S

PI_M

ISO

TN_S

PI_S

CK

TN_S

PI_M

OSI

TN_S

PI_M

ISO

TN_S

PI_S

CK

P3V

TN_S

PI_C

S_SD

TN_S

PI_C

S_SD

TN_B

OLT

_IN

DTN

_GPI

O

TG_R

ESET

RST

1

VDD

2

VSS

3

U19

MC

P130

T-27

0I/T

T

P3V

TN_E

VR

EF

SW5

AD

TSM

62R

VTR

Tin

yNod

e

GPS

_Tpu

lse

P3V

TG_R

ESET

TG_P

RO

G

TG_U

AR

T_TX

DTG

_UA

RT_

RX

D

TN_S

PI_S

CK

TN_S

PI_M

OSI

TN_S

PI_M

ISO

TN_S

PI_S

CK

TN_S

PI_M

ISO

TN_S

PI_M

OSI

TN_B

OLT

_REQ

Har

ting

0918

-510

-632

4

1 2 3 4 5 6 7 8 9 10

S14

SIP-

5x2

R21 4k

7TN

_BO

LT_A

CK

TN_B

OLT

_MO

DE

100u

C66

C56

100n

FC

6410

0nF

R29

100k

P3V

C73

10uF

P3V

SD_D

21

SD_D

3/C

S2

SD_C

MD

/MO

SI3

VDD

4

CLK

/SC

LK5

VSS

6

SD_D

0/M

ISO

7

SD_D

18

CD

9

CD

_VSS

10

Shie

ld

J5M

icro

SD h

olde

r

C15

10nF

R22

100k

Q5

FDC

638P

P3V

_TN

_PER

IPH

SW_T

N_P

ERIP

H

SW_T

N_P

ERIP

H

C75

10nF

Not

fitte

d

Not

fitte

d

Not

fitte

d

PIC1501 PIC1502 CO

C15

PIC5601 PIC5602 CO

C56

PIC6401 PIC6402 CO

C64

PIC6601 PIC6602 CO

C66

PIC7301 PIC7302 CO

C73

PIC7

501

PIC7

502

COC75

PIJ2

01

PIJ202

PIJ2

03

PIJ204

PIJ2

05

PIJ206

PIJ207

PIJ208

PIJ209

PIJ2

010

PIJ2

011

PIJ2

012

PIJ2

013

PIJ2

014

PIJ2

015

PIJ2

016

PIJ201

7 PI

J201

8 PI

J201

9 PI

J202

0

PIJ2

021

PIJ2

022

PIJ2

023

PIJ2

024

PIJ2

025

PIJ2

026

PIJ202

7 PI

J202

8 PI

J202

9 PI

J203

0

PIJ20Screw

COJ2

PIJ501

PIJ502

PIJ503

PIJ504

PIJ505

PIJ506

PIJ507

PIJ508

PIJ509

PIJ5010

PIJ50Shield

COJ5

PIQ501

PIQ502

PIQ503 PIQ504

PIQ505

PIQ506

COQ5

PIR2101 PIR2102 COR21

PIR220

1 PIR

2202

COR22

PIR2901 PIR2902 COR2

9

PIS1

101

PIS1

102

PIS110

3

COS11

PIS1

301

PIS1

302

PIS1

303

PIS130

4 PIS

1305

PIS1

306

PIS1

307

PIS1

308

PIS130

9 PI

S130

10

PIS1

3011

PIS1

3012

PIS1

3013

PIS130

14

COS13

PIS1

401

PIS1

402

PIS140

3 PIS

1404

PIS1

405

PIS1

406

PIS1

407

PIS140

8 PI

S140

9

PIS1

4010

COS14

PISW501 PISW503 COSW

5

PIU1801

PIU1802

PIU1

803

PIU1804

PIU1

805

PIU1806 COU1

8

PIU1

901

PIU1902

PIU1903 COU1

9

PIC1501

PIC5601 PIC6401

PIC6601

PIC7301

PIC7

502

PIJ206

PIJ20Screw

PIJ506

PIJ50Shield

PIS130

9

PIS1

4010

PISW501

PIU1801

PIU1903

PIJ204

PIJ2

010

PIJ2

012

PIJ2

013

POGP

S0Tp

ulse

PI

J201

5

PIJ201

7 PI

J201

9 PI

J202

0

PIR2101 PIU1802

PIJ2

022

POTN

0BOL

T0IN

D PI

J202

3

POTN0BOLT0REQ

PIJ2

024

POTN0GPIO

PIJ2

026

PIJ202

7 POTN0BOLT0ACK

PIJ2

028

PIJ2

029

POTN0BOLT0MODE

PIJ2

030

POTN0EVREF

PIJ501

PIJ508

PIJ509

PIJ5010

PIS1

306

PIS1

308

PIS1

3010

PIS1

3012

PIS1

3013

PIS130

14

PIS1

406

PIS1

407

PIS140

8 PI

S140

9

PIU1

803

PIU1804

PIU1

805

PIU1806

PIC5602 PIC6402

PIC6602

PIC7302

PIJ202

PIQ504

PIR220

2

PIR2902

PIS1

102

PIS1

401

PIU1902

PIC1502 PIJ504

PIQ501

PIQ502

PIQ505

PIQ506

PIR2102

NLP3V0TN0PERIPH

PIC7

501

PIJ2

021

PIQ503 PIR

2201

NLSW0TN0PERIPH

PIJ207

PIS1

307

PIS1

405

NLTG

0PRO

G

PIJ208

PIS1

3011

PIS140

4

PISW503 PI

U190

1

NLTG

0RES

ET

POTG

0RES

ET

PIJ2

011

PIS140

3 NLTG0UART0RXD

PIJ209

PIS1

402

NLTG

0UAR

T0TX

D

PIJ2

025

PIJ502

NLTN0SPI0CS0SD

PIJ2

016

PIJ507

PIR2901

NLTN0SPI0MISO

POTN0SPI0MISO

PIJ2

014

PIJ503

NLTN0SPI0MOSI

POTN0SPI0MOSI

PIJ2

018

PIJ505

NLTN

0SPI

0SCK

POTN0SPI0SCK

PIJ2

03

PIS1

303

NLTN

0TDI

PIJ2

01

PIS1

301

NLTN

0TDO

PIJ2

05

PIS130

5 NL

TN0T

MS

PIS1

101

PIS130

4 NLVCC0TARGET

PIS110

3

PIS1

302

NLVC

C0TO

OL

POGP

S0Tp

ulse

POTG

0RES

ET

POTN0BOLT0ACK

POTN

0BOL

T0IN

D

POTN0BOLT0MODE

POTN0BOLT0REQ

POTN0EVREF

POTN0GPIO

POTN0SPI0MISO

POTN0SPI0MOSI

POTN0SPI0SCK