MAPIC Summer Project 2019

Summary

A software package for wireless control and DAQ from the MAPIC using a Pyboard D SF3W. Current features and perforamance include:

• Wifi communication using python socket network module/UDP. Maximum data transfer rate determined to be > 95Mb/s.
• Read and write to two I2C potentiometers at addresses 0x2C and 0x2D. Also scan for I2C addresses.
• Python level interrupt measurements with ADC, in addition to high performance DMA interrupt peakfinding code integrated into Micropython.
• Histogram generation and display in real time.
• Python Tkinter GUI for control and readout.
• Config file to edit default settings and save setup for repeat measurments.

Python Setup

First install python version 3.7.4 In order to install dependencies, first ensure that python 3 is installed (with pip) and added to PATH. Then open command prompt inside the folder containing requirements.txt and parse the command:

$ pip install -r requirements.txt

In linux or the event that you have both python 2 and 3 installed, you may find that you will need to specify pip3 explicitly:

$ pip3 install -r requirements.txt

This installs the following packages for python 3:

• numpy
• pyserial
• matplotlib
• scipy
• pyusb -> used for flashing firmware to the board

If this doesn't work, one can install each individually with the command:

$ pip install <module>

Flashing Micropython Firmware

This repo relies on a customised fork of the micropython Github found here, specifically the mpdma branch . In order to flash new firmware to the Pyboard D SF3W board, you need to have an ARM compiler installed, the recommended package is arm-none-eabi-gcc. This can be installed through the command,

$ sudo apt-get install arm-none-eabi-gcc

There is also a windows/linux compiler available for download at https://launchpad.net/gcc-arm-embedded or using linux command line with https://launchpad.net/~team-gcc-arm-embedded/+archive/ubuntu/ppa

Once installed, navigate to the root folder and then execute the following command to build the micropython cross-compiler.

$ make -C mpy-cross

Then, edit the first line in the Makefile in the ~/ports/stm32 directory so that it reads,

BOARD ?= PYBD_SF3

Finally, navigate to the ~/micropython directory and parse the following to compile the build,

$ git submodule update --init
$ cd ports/stm32
$ make
$ sudo make deploy

Note that steps other than the final two only need to be carried out once to set up the library.

Custom Micropython Code

Added a new custom functions to adc.c. There have also been some changes to ADC class in order to facilitate changing the ADC mode. To set up our ADC object we use the code:

# Necessary imports
from pyb import ADC
from machine import Pin

adcpin = Pin("X12")             # set up ADC pin object on pin PIN
adc = ADC(adcpin, mode)         # create ADC object with the ADC pin, triple mode false

# mode can be "SingleDMA", "TripleDMA", "Single".
# "Single" -> Can use adc.read_timed 
# "SingleDMA" -> Can use adc.read_dma
# "TripleDMA" -> Can use adc.read_interleaved

Two more sampling modes have been added in the custom firmware, called read_dma and read_interleaved.

adc = ADC(adcpin, "TripleDMA")      # create ADC object with the ADC pin, triple mode
adc.read_interleaved(num_samples,ipv4)
# adc.read_interleaved(num_samples,ipv4)
# num_samples : integer number of peaks to sample, ideally multiple of 360
# ipv4 : IPV4 address tuple e.g. ("192.168.1.1",5000) 
# returns nothing

adc = ADC(adcpin, "SingleDMA")      # create ADC object with the ADC pin, triple mode
adc.read_dma(num_samples,ipv4)
# adc.read_interleaved(num_samples,ipv4)
# num_samples : integer number of peaks to sample, ideally multiple of 360
# ipv4 : IPV4 address tuple e.g. ("192.168.1.1",5000) 
# returns nothing

adc.deinit_setup()            # deinit the adc peripheral, clear configuration
adc = ADC(adcpin, mode)       # reinitialise the adc object with desired mode

Operation

• Connect to the Wi-Fi access point "PYBD" on the readout system.
• Launch the MAPIC.bat file to start the GUI from which one can control the MAPIC and take measurements

Useful Links

Python Links

This application requires knowledge and use of the following python libraries/implementations in addition to those installed through pip:

• Tkinter used for the Python GUI.
• Python Socket API for data transfer with the board.
• Micropython Language Docs for python development on the board.
• Micropython for the Pyboard D Pyboard D specific features.

C Links

Links to specific C apis used in the development of this project, as well as some more detailed instructions on micropython development.

• STMCUBE32F7 HAL libraries used for coding micropython/board control.
• lwIP UDP API lightweight C socket API, used with python sockets for data streaming.
• Micropython C modules more detailed explanations/examples on how to develop micropython functions.

Hardware Links

Relevant data sheets and technical documentation for the Pyboard D SF3 chip.

• STM32F72(3)xxx Reference Manual
• STM32F723IEK Datasheet