This document discusses using ARM development boards for physical experimental instruments. It provides examples of the Raspberry Pi and STM32 microcontrollers, comparing their interfaces, development environments, and use in prototypes that require high-speed digital-to-analog and analog-to-digital conversion with Ethernet connectivity. Prototypes achieved update times of 5us or less while maintaining real-time data transfer capabilities. Future plans include higher resolution converters and combining STM and Raspberry Pi units for scalable real-time control.

1. Using ARM Dev.Board
in physical experimental
instruments
IoT 2015 Bar Montenegro
Andrey Novikov, msc-cg

2. mass spectrometry
Sector MS (1936)
Time of Flight MS (1948)
Quadrupole (1970)
deflection

3. Sector Mass-Spectrometer

4. ToF MS

5. Quadrupole

6. 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

7. 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

8. Interfaces
microcontroller 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

9. Development Boards
• Raspberry Pi
• Arduino
• ST32F
• STM discovery dev board
• Mountaineer
• OLIMEX

10. Raspberry Pi-2
A 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)

11. 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) ;

12. 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

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

14. ST Microelectronics

15. STM32F407
STM407 Discovery Board
with Extension Board
ST-Link
Mountaineer
NETMF
.NET BootLoader
OLIMEX
STM32-E407
USB-DFU
Bootloader

16. 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

17. STM SDK
Open 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

18. STM32F4Cube
Resolving Pin Conflict
Generating Pin Report
Template Projects:
• EWARM
• MDK-ARM V4
• MDK-ARM V5
• TrueStudio
• SW4STM32

19. Prototype 1
based 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

20. 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

21. 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

22. PC-end software

23. 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

24. Conclusions
Modern 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