micropython-samples

A place for assorted code ideas for MicroPython. Most are targeted at the Pyboard variants.

fastbuild - Pull and build Pyboard firmware under Linux

These scripts are intended to speed and simplify rebuilding firmware from source notably where pyboards of different types are in use, or when frozen bytecode necessitates repeated compilation and deployment. In particular buildpyb will detect the attached Pyboard type, build the appropriate firmware, put the board into DFU mode and deploy it, before launching rshell. The latter step may be removed if rshell is not in use.

The scripts should be run as your normal user and can proceed without user interaction.

Includes udev rules to avoid jumps from /dev/ttyACM0 to /dev/ttyACM1 and ensuring Pyboards of all types appear as /dev/pyboard. Rules are also offered for USB connected WiPy (V1.0) and FTDI USB/serial adaptors.

These scripts use Python scripts pyb_boot to put the Pyboard into DFU mode and pyb_check to determine the type of attached board. These use the pyboard.py module in the source tree to execute scripts on the attached board.

Optional Edits

In the buildpyb script you may wish to edit the -j 8 argument to make. This radically speeds build on a multi core PC. Empirically 8 gave the fastest build on my Core i7 4/8 core laptop: adjust to suit your PC. You may also want to remove the call to rshell if you don't plan on using it.

This script defaults to a frozen modules directory stmhal/modules. This may be overridden by creating an environment variable FROZEN_DIR: a recent update enabled the directory for frozen to be located anywhere in the filesystem, allowing project specific directories.

In buildnew you may wish to delete the unix make commands.

Dependencies and setup (on PC)

Python3
The following Bash code installs pyserial, copies 49-micropython.rules to (on most distros) /etc/udev/rules.d. It installs rshell if you plan to use it (recommended).

As root:

apt-get install python3-serial
pip install pyserial
cp 49-micropython.rules /etc/udev/rules.d
pip3 install rshell

Verify that pyboard.py works. To do this, close and restart the terminal session. Run Python3, paste the following and check that the red LED lights:

import os
mp = os.getenv('MPDIR')
sys.path.append(''.join((mp, '/tools')))
import pyboard
pyb = pyboard.Pyboard('/dev/pyboard')
pyb.enter_raw_repl()
pyb.exec('pyb.LED(1).on()')
pyb.exit_raw_repl()

The build scripts expect an environment variable MPDIR holding the path to the MicroPython source tree. To set this up, as normal user issue (edited for your path to the MicroPython source tree):

cd ~
echo export MPDIR='/mnt/qnap2/data/Projects/MicroPython/micropython' >> .bashrc
echo >> .bashrc

Close and restart the terminal session before running the scripts.

Build script: buildpyb

This checks the attached pyboard. If it's a V1.0, V1.1 or Lite it builds the correct firmware and deploys it. Otherwise it produces an error message.

Optional argument --clean - if supplied does a make clean to delete all files produced by the previous build before proceeding.

Update source: buildnew

Report state of master branch, update sources and issue make clean for Pyboard variants, and ESP8266. Builds cross compiler and unix port.

ESP8266 Build

buildesp A script to build and deploy ESP8266 firmware. Accepts optional --clean argument.

ssd1306

A means of rendering multiple larger fonts to the SSD1306 OLED display. See docs.

mutex

A class providing mutual exclusion enabling interrupt handlers and the main program to access shared data in a manner which ensures data integrity.

watchdog

Access the simpler of the Pyboard's watchdog timers.

reverse

Fast reverse a bytearray in Arm Thumb assembler.
Python code to bit-reverse (fast-ish) 8, 16 and 32 bit words.

ds3231_pb

Driver for the DS3231 low cost precison RTC, including a facility to calibrate the Pyboard's RTC from the DS3231. Calibration to high precision may be achieved in five minutes.

Buildcheck

Raise an exception if a firmware build is earlier than a given date.

timed_function

Time a function's execution using a decorator.

ESP8266

benchmark.py Tests the performance of MQTT by periodically publishing while subscribed to the same topic. Measures the round-trip delay. Adapt to suit your server address and desired QOS (quality of service, 0 and 1 are supported). After 100 messages reports maximum and minimum delays.

conn.py Connect in station mode using saved connection details where possible.

Rotary Incremental Encoder

Classes for handling incremental rotary position encoders. Note that the Pyboard timers can do this in hardware. These samples cater for cases where that solution can't be used. The encoder_timed.py sample provides rate information by timing successive edges. In practice this is likely to need filtering to reduce jitter caused by imperfections in the encoder geometry.

There are other algorithms but this is the simplest and fastest I've encountered.

These were written for encoders producing TTL outputs. For switches, adapt the pull definition to provide a pull up or pull down as required.

The encoder.portable.py version should work on all MicroPython platforms. Tested on ESP8266. Note that interrupt latency on the ESP8266 limits performance (ESP32 is probably similar).

A pseudo random number generator

On the Pyboard V1.1, true random numbers may be generated rapidly with pyb.rng() which uses a hardware random number generator on the microcontroller.

There are two use cases for the pseudo random number generator. Firstly on platforms lacking a hardware generator (e.g. the Pyboard Lite). And secondly where repeatable results are required, for example in testing. A pseudo random number generator is seeded with an arbitrary initial value. On each call to the function it will return a random number, but (given the same seed) the sequence of numbers following initialisation will always be the same.

See the code for usage and timing documentation.

A design for a hardware power meter

This uses a Pyboard to measure the power consumption of mains powered devices. Unlike simple commercial devices it performs a true vector (phasor) measurement enabling it to provide information on power factor and to work with devices which generate as well as consume power. It uses the official LCD160CR display as a touch GUI interface. It is documented here.

License

Any code placed here is released under the MIT License (MIT).
The MIT License (MIT)
Copyright (c) 2016 Peter Hinch
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.