S14_ Data Acquisition Using CAN Bus - Embedded Systems Learning Academy

8/10/2019 S14_ Data Acquisition Using CAN Bus - Embedded Systems Learning Academy

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S14: Data Acquisition using CAN bus

From Embedded Systems Learning Academy

Contents

1 Project Title2 Abstract3 Objectives & Introduction

3.1 Team Members & Responsibilities4 Schedule5 Parts List & Cost6 Design & Implementation

6.1 Hardware Design and Implementation6.2 Description of parts6.3 Hardware Implementation at each NODE6.4 Software Design and Implementation

7 Testing & Technical Challenges8 Conclusion

8.1 Project Video8.2 Project Source Code

9 References9.1 Acknowledgement9.2 References Used

Project Title

Data Acquisition using CANbus

AbstractOur project is to implement a high speed data acquisition system using CAN and perform tasks according to the data received.

Our system will collect data from sensors over multiple nodes and transmit the data over the CAN bus. The CAN packets are

received by a single node which will do the required functionality as desired by the application.The LEDs at the receiver node

simulate the functions which ca be done using the data acquired over the CAN bus.The purpose is to gather all the data

simultaneously over the CAN bus and implement hardware filtering to manage the data packets on the CAN bus

Figure 1 shows the system block diagram:


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Objectives & Introduction

The objective of this project to implement CAN bus and establish communication between devices.Our idea is to use use 6 degree

of freedom MPU-6050 sensor as motion/gesture, ultrasonic range finder HC-SR04 as obstacle detector for data harvesting andsending these data over the CAN bus. Specific movement/range will trigger predefined tasks and transmit the control to different

LEDs. According to the direction of the accelerometer and its tilt movement, as well as ultrasonic sensor distance, specific

application at the third node would be done.

Team Members & Responsibilities

Shweta BohareCan bus Interface

Mradula NayakCan bus Interface

Heng Zhang

6 DOF and Ultrasonic sensors

All TeamFreeRTOS Software Design3D on the computer

Schedule
http://www.socialledge.com/sjsu/index.php?title=File:244_DataAcquisitionusing_CAN_BlockDiag.jpg


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Week# Start Date End Date Task Actual

1 2/25 3/18 Order sensors

System design Completed.Other parts are ordered.

2 3/18 3/26 Self-Loop testing of CAN Bus Completed.

4 3/27 4/13 Write on microSD SPI microSD I/O Initial write on SD-card is done.

5 4/6 4/12 Interfacing ultrasonic sensor with the board. Done

6 4/13 4/27 Accelerometer data transmission between 2-Boards. Done

7 4/22 4/27 Communication between 3 CAN Nodes Done

8 4/28 5/5 Testing and remove bugs, further enhancements Done

9 5/22 5/22 Demo

Parts List & Cost

Parts Cost Comment

SJ One Board[1] (http://www.socialledge.com/sjsu/index.php?title=SJ_One_Board) $80.00

x3

Each

board uses

for

different

functions

GY 521 board(MPU-6050) $5.90

x1

6 DOF

motion

sensor

TJA1049TK[2]

(http://www.nxp.com/products/interface_and_connectivity/transceivers/can_transceivers/TJA1049TK.html)

$0.00

x4 free

samples

high-speed

CAN

transceiver

HC-SR04[3] (http://www.micropik.com/PDF/HCSR04.pdf)

$3.00

x1 free

samples

Ultrasonic

ranging

module

Total Cost $249.00Keep it

low

Design & Implementation

Hardware Design and Implementation

In our project we are using three nodes to communicate over a CAN bus. The CAN Controller is embedded on the SJ-ONE board

which transmits the microcontroller logic signals to CAN transceiver. The CAN transceiver is a voltage converter which transmits

the data on CAN bus by converting it into electrical signals required for CAN. The CAN tranceiver requires a 5V supply for its

working. Hence we have designed a Power Circuit to provide 5V dc to the CAN transceiver. In the project, data is acquired from

two sensors, each connected to separate nodes. We are using MPU-6050 which is interfaced with Node 1 via I2C protocol.

Ultrasonic sensor HC-SR04 is connected to Node 2 which detects the distance of an object from the sensor. The receiver nodegets the data from Node 1 and Node 2 and it simulates the data on the LEDs connected.

Description of parts
http://www.micropik.com/PDF/HCSR04.pdfhttp://www.socialledge.com/sjsu/index.php?title=SJ_One_Boardhttp://www.nxp.com/products/interface_and_connectivity/transceivers/can_transceivers/TJA1049TK.html


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Power supply Circuit

MCP2551

MPU6050

Power Supply: LM7805

An LM7805 linear regulator IC is used for this purpose. It converts a DC input

voltage of range 7-25 V to a stable +5 V. It requires just two external capacitors and is

very easy to useThe input DC voltage for LM7805 could be obtained from a 9V DC

wall adapter that can supply 1 Amp of load current.We need the 5 volt supply for all

the external ICs have been used in this project like MCP2551 and MPU6050.The

following schematic is generate the 5Volt regulated power.

CAN transceiver: MCP2551

The MCP2551 is a high-speed CAN, fault-tolerant device that serves as the interface between

a CAN protocol controller and the physical bus. The MCP2551 device provides differential

transmit and receive capability for the CAN protocol controller, and is fully compatible with

the ISO-11898 standard, including 24V requirements. It will operate at speeds of up to 1

Mb/s. It is used for following functions:

1. As a Transmitter: It operates in two states Dominant and Recessive. When differential

voltage between CANH and CANL is less than 102 V it operated in dominant mode, and

when the voltage difference is less than 1.2 volt it operates in Recessive mode. These both

modes are corresponds to the TXD pin.

2. Maximum nodes: allowing a maximum of 112 nodes to be connected.

3. Receiver Function: The RXD output pin reflects the differential bus voltage between CANH and CANL. The Low and Highstates of the RXD output pin correspond to the Dominant and Recessive states of the CAN bus, respectively.

4. Operations.High speed flow control and standby. High-Speed mode is selected by connecting the RS pin to VSS. In this mode,

the transmitter output drivers have fast output rise and fall times to support high-speed CAN bus rates. The slope, or slew rate

(SR), is controlled by connecting an external resistor (REXT) between RS and VOL (usually ground). The device may be placed

in Standby or SLEEP mode by applying a high-level to the RS pin.

MCP2551 (http://www.sparkfun.com/datasheets/DevTools/Arduino/MCP2551.pdf)

Motion Sensor: MPU-6050

The MPU-6050 is a motion sensor that combines two chips: the MPU-6050, which contains a 3-axis

gyroscope, 3-axis accelerometer and an onboard Digital Motion Processor. Although the built-in processor is

integrated with 6-axis MotionFusion algorithms, such as Kalmann filter, it is not open source. As a result, we

simply use MPU-6050 as a 6 DOF motion sensor and renders high resolution 6 DOF informations to the SJ-

One board for further usage. When developing the MPU driver, we refer to the sparkfun github site: (1.

https://github.com/sparkfun/MPU-6050_Breakout 2. http://www.botched.co.uk/pic-tutorials/mpu6050-setup-

data-aquisition/) as well as the given drivers in SJSU-Dev by Professor Preetpal Kang. It is communicate

with SJ-One board via I2C ports.

Ultrasonic Sensor: HC-SR04

The Ultrasonic Ranging Module HC-SR04 is a low power simple module, with 4 ports: VCC(5V), GND, Trig(input),

Echo(output). It is connected to the SJ-One board through GPIO pins, since it doesn't have protocols. Whenever we need to
http://www.socialledge.com/sjsu/index.php?title=File:CMPE244_S14_REGULATED_POWER.jpghttp://www.botched.co.uk/pic-tutorials/mpu6050-setup-data-aquisition/http://www.socialledge.com/sjsu/index.php?title=File:CMPE244_DA_CAN_MCP2551.jpghttps://github.com/sparkfun/MPU-6050_Breakouthttp://www.socialledge.com/sjsu/index.php?title=File:CMPE244_DA_CAN_MPU6050.jpghttp://www.sparkfun.com/datasheets/DevTools/Arduino/MCP2551.pdf


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HC-SR04

Pin interface on each Node

Node 1

Node 2

Node 3

measure the range, we supply a short 10 us Pulse to the trigger input to invoke this sensor then it will send out 8 cycle burst of

ultrasound at 40 kHz so as to receive its echo. The formula to calculate the distance is through the time intervals from trigger

signals and the echo signals by: us/58 = centimeters.

Hardware Implementation at each NODE

Node 1

On node 1, we haveconnected MPU-6050 on

I2C2 of SJONE-Board.

CAN transceiver is

connected on CAN1 of

SJONE- board. A

terminating resistor is also

connected to the CAN

transceiver of Node1.

Node 2

On node 2, we have

connected HC-SR04 on

GPIO pins P1.6 and P1.7.It transmits the distance of

the object over the CAN bus. CAN transceiver with

terminating resistor is also connected on this node.

Node 3

On node 3, we have connected the CAN transceiver on CAN1

of SJONE- board. We have connected 5 LEDs, one for

distance from ultrasonic sensor on Node 2 and other 4 LEDs

determine the tilt of the object on Node 1.
http://www.socialledge.com/sjsu/index.php?title=File:CMPE244_S14_DA_CAN_Interfacing.jpghttp://www.socialledge.com/sjsu/index.php?title=File:CMPE244_S14_NODE2.jpghttp://www.socialledge.com/sjsu/index.php?title=File:CMPE244_S14_DA_CAN_PinInterface.jpghttp://www.socialledge.com/sjsu/index.php?title=File:CMPE244_S14_NODE1.jpghttp://www.socialledge.com/sjsu/index.php?title=File:CMPE244_S14_NODE3.jpghttp://www.socialledge.com/sjsu/index.php?title=File:CMPE244_S14_HC-SR04.jpg


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Software Design and Implementation

In our project, every node has to compute the data and transmit it over the CAN bus. For proper synchronization of the

transmission, we have divided each function into tasks which communicate via Queues. We have utilized FreeRTOS API for

managing the tasks and queues.

Software implementation is done using:

1. CAN driver2. I2C driver for MPU-60503. Ultrasonic sensor trigerring

1.CAN driver

CAN is a high-speed data bus for deterministic communication.It transmits at 100k,250k, 500k and 1Mbit speeds.CAN nodes

communicate by transferring CAN frames and each node has a ID associated with it. The ID for each node is developed in the

program. CAN bus works in the following modes: 1. OFF MODE: It does not accept any message from any node. 2. BYPASS

MODE: It accepts all the messages that it receives. 3. Acceptance Filtering: It accepts only the specific messages of the id stored

in its RAM.

In our design, we have 2 transmitter nodes and one receiver node. Hence we have implemented Acceptance filtering at the

receiver node to acknowledge the messages of the transmitter nodes. The transmitting nodes are in OFF mode,as it need not

receive any messages from the other transmitter node.

FLOW DIAGRAMS EXPLAINING TRANSMITTER AND RECEIVER FLOW DIAGRAM

Can transmitter driver
http://www.socialledge.com/sjsu/index.php?title=File:CMPE244_DA_CAN_CANtx.jpg


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Can receiver driver

2. I2C driver for MPU-6050

At node 1, the I2C driver is written to interface with MPU-6050. The device address of MPU-6050 is 0x69. The I2C state machine

goes through different dtages to read from data from MPU-6050. The configuration resistors of MPU-6050 is first set. Since we

are only reading accelerometer values, we are only reading the 16-bit registers of X,Y, Z-axis.

The Tasks at Node 1 are performing the functions in the following manner:
http://www.socialledge.com/sjsu/index.php?title=File:CMPE244_DA_CAN_CANrx.jpg


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Node1

3. Ultrasonic sensor trigerring

At node 2, we are getting the distance of the object from the node using an ultrasonic sensor. An ultrasonic burst is triggered using

a Trigger pin on the sensor module. The receiver part of the sensor then listens for the echo return pulse. An Echo pin on the

sensor remains at HIGH voltage level during the time and the distance of the object can be calculated from this duration. Distance

of the object is calculated using the formula: Distance = ((Time taken) * 340m/s) /

The tasks at Node 2 are performed as follows:
http://www.socialledge.com/sjsu/index.php?title=File:CMPE244_DA_CAN_Node1SFFLOW.jpg


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Node2


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At node 3, there are LEDs which work according to the data sent over from the two nodes. The tasks are distributed as follows:

Node3

Testing & Technical Challenges

Hardware issues

1. During self loop, we recognized that there has to be a 1K resistor at the Rs pin of transceiver which has to be connected to

ground.

2. Designing of power supply took a lot of time. We designed a separate power supply to provide continuous 5V supply.3. Due to improper connections of transceiver and power supply, the CAN transceiver IC was burnt and we had to replace it many

times.

Software issues

1.The mode register of CAN was not getting written because of error in clock set. We set the clock source to 2 in sys_config.h.

2.The CMR register was not set during self loop, because of which the CAN transmission had not started.

3.The data sent from the sensors had to be sent to CAN controller and at the receiver node proper timing delay had to be put to

process the data from two nodes.

4.Hardware filtering didn't work for a lot of time due to a error in the CAN driver. We have written a separate piece of code to set

the hardware filtering.

5.Reading serial data from SJONE- board to plot on MATLAB or processing software was not successful since the board was

getting reset once the port was opened.

Conclusion


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Documents

S14_ Data Acquisition Using CAN Bus - Embedded Systems Learning Academy