Using ARM Dev.Board in physical experimental

instruments IoT 2015 Bar Montenegro

Andrey Novikov, msc-cg

mass spectrometry

Sector MS (1936)Time of Flight MS (1948)

Quadrupole (1970)

deflection

Sector Mass-Spectrometer

ToF MS

Quadrupole

What we had before• static voltages on lenses

• FTDI USB-I2C bus

• 2-20ms per command

• 1-2% of lost commands

• update frequency 5-10Hz

Requested Specification • Change Voltage 2-4 channels every 10-20us (precision

16bit 0.1mV/10V)

• Measure 1 Voltage (16-24bit) channel on each step.

• measured data samples without time gaps for 1s (100000 samples on that frequency)

• transfer all acquired data less then 10ms to the PC.

• be ready for new cycle.

• should be easily scalable

Interfacesmicrocontroller layer digital Interfaces

• GPIO - General Purpose Input Output

• SPI - Serial Peripheral Interface

• I2C(TWI) - two ware interface

PC layer connection data transfer interface

• Ethernet 10/100Mb

• RS-232

• RS-485

Development Boards• Raspberry Pi

• Arduino

• ST32F

• STM discovery dev board

• Mountaineer

• OLIMEX

Raspberry Pi-2A 900MHz quad-core ARM Cortex-A7 1GB RAM 4 USB ports 40 GPIO pins Full HDMI port Ethernet port 10/100 Combined 3.5mm audio jack and composite video Camera interface (CSI) Display interface (DSI) Micro SD card slot VideoCore IV 3D graphics core

Linux Distros: • Rasbian (Debian) • Pidora(Fedora) • Arch Linux (Pi build) • Ubuntu 14 (for Pi2)

Raspberry Pi code example#Python import RPi.GPIO as GPIO import time def main(): # Main program block GPIO.setmode(GPIO.BCM) # GPIO.setup(LCD_E, GPIO.OUT) # E GPIO.setup(LCD_RS, GPIO.OUT) # RS GPIO.setup(LCD_D4, GPIO.OUT) # DB4 GPIO.setup(LCD_D5, GPIO.OUT) # DB5 GPIO.setup(LCD_D6, GPIO.OUT) # DB6 GPIO.setup(LCD_D7, GPIO.OUT) # DB7 #etc…

def lcd_byte(bits, mode): # Send byte to data pins # bits = data # mode = True for character # False for command GPIO.output(LCD_RS, mode) # RS # High bits GPIO.output(LCD_D4, False) GPIO.output(LCD_D5, False) GPIO.output(LCD_D6, False) GPIO.output(LCD_D7, False) #etc…

//C int mcp3008Spi::spiOpen(std::string devspi){ int statusVal = -1; this->spifd = open(devspi.c_str(), O_RDWR); if(this->spifd < 0){ perror("could not open SPI device"); exit(1); } statusVal = ioctl (this->spifd, SPI_IOC_WR_MODE, &(this->mode)); if(statusVal < 0){ perror("Could not set SPIMode (WR)...ioctl fail"); exit(1); } //etc…

// Transfer data with SPI: one spi transfer for each byte for (i = 0 ; i < length ; i++){ spi[i].tx_buf = (unsigned long)(data + i); // transmit from "data" spi[i].rx_buf = (unsigned long)(data + i) ; // receive into "data" spi[i].len = sizeof(*(data + i)) ; spi[i].delay_usecs = 0 ; spi[i].speed_hz = this->speed ; spi[i].bits_per_word = this->bitsPerWord ; spi[i].cs_change = 0; } retVal = ioctl (this->spifd, SPI_IOC_MESSAGE(length), &spi) ;

using RPi?

Linux Data Server/Desktop

• Pros

• low power consumption

• small size

• full functional Linux

• Cons

• SD rewrite limit

Linux Dev.Board

• Pros

• self-sufficiency

• scalable

• SPI & I2C present on board

• Cons

• few digital interface ports

• on linux kernel delay 100us

ChibiOs or RTOS Dev.Board

Arduino Arduino UnoMicrocontroller

ATmega328 8-bit AVR RISC-based 20MHz I2C x1SPI x2 UART x1 ADC: 8ch 10bit 15kbps Arduino Uno with Eth shield

ST Microelectronics

STM32F407

STM407 Discovery Board with Extension Board

ST-Link

Mountaineer NETMF

.NET BootLoaderOLIMEX

STM32-E407 USB-DFU

Bootloader

IDE• Keil http://www.keil.com

• CooCox CoIDE http://www.coocox.org

• .NET MicroFramework http://www.netmf.com

• Arduino IDE https://www.arduino.cc/en/Main/Software

• GNU C Compiler

STM SDKOpen Source SDK includes:

• Easy to use and well documented periphery functions. GPIO, I2C, SPI

• Very difficult to use(based on callbacks) LwIP library - so sth-stack in STM is a pain

• RTOS library:

• have tcp-ip socket

• but task scheduler some times freezes all tasks up to 10ms

• it’s “ortodox” Ansi C 99

STM32F4CubeResolving Pin Conflict Generating Pin Report Template Projects: • EWARM • MDK-ARM V4 • MDK-ARM V5 • TrueStudio • SW4STM32

Prototype 1based on stm32f407 discovery DAC: AD5544 4ch 16bit ADC: TLC4541 1ch 16bit ETH+Disp: Discovery Ext.Board IDE: Keil v4.74

time spent: programmer:

4 weeks electronics engineer:

2 weeks

time spent: programmer:

4 weeks electronics engineer:

2 weeks

time spent: programmer:

4 weeks electronics engineer:

2 weeks

Prototype 2 (failed)DAC: AD5668 8ch 16bit ADC: AD7606 8ch 16bit ETH: LAN8720 acid etched PCB

didn’t worked correctly because of huge amount of breakthroughs, but SW algorithms worked through

time spent: programmer:

4-6 weeks electronics engineer:

2-3 weeks

Pre-Release

• 8x Paired ADC-DAC • 5us update time • 1ms command

response time • approved 100MB

transfer speed • ETH-I2C bus

translator

DAC: AD5668 8ch 16bit ADC: ADAS3023 8ch 16bit ETH: LAN8720 two side factory printed PCB

PC-end software

In Plans• using individual 18-24bit ADC for signal registration

• adding eth-events handler to sync state between stm units

• combine Real-Time STM units and RaspberryPi2 as a central control node under Linux

• DDA - Data Dependent Acquisition

• finish “home dark-server” based on RPi-2

ConclusionsModern Microelectronics is:

• Easy to understand (entrance threshold is very low)

• Easy scale (a lot of standard interfaces that you can just use)

• easy to buy (cheap and wide choice)

• really fun and interesting