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About Adafruit_Micropython_Blinka

This repository is structured around integration tests rooted at the test/src directory, intended to test the compatibility layer rooted in src.

The tests offer a procedural way to assert equivalence between 'native' CircuitPython behaviour and behaviour of the adafruit_blinka compatibility layer.

The structure of the testing modules permits test suites to be imported and configured selectively on different implementations, platforms and boards (see for definitions of these terms).

Automated introspection of the python runtime combines with interactive prompts to configure a scenario for testing (e.g. which platform, which board, what is wired to it) so the same routines can be carried out on Micropython boards, dual boards running either CircuitPython or Micropython, or dedicated CircuitPython boards.

Typically the tests have first run on a native CircuitPython platform, and are then used to prove equivalence on a Micropython platform running the adafruit_blinka compatibility layer.

Tests so far

Tests of compatible versions of digitalio, board and microcontroller have successfully demonstrated the same code running on either platform, setting and getting pin values and using pull.

Tests have also proven compatibility of the following unmodified CircuitPython libraries...

  • adafruit_bme280
  • adafruit_mma8451
  • adafruit_gps

...which proves the fundamentals of bitbangio.I2C, busio.I2C and busio.UART


To take a minimal example, the following should assert the default behaviour of the DigitalInOut constructor, checks the behaviour of switch_to_input/output(), configures a pin as a pull-up button, a pull-down button and an LED.

from testing import test_module_name

Or to take a more involved example of constructing a test suite requiring hardware, the following should verify I2C communication with a BME280 module.

import unittest
import testing.universal.i2c
suite = unittest.TestSuite()
runner = unittest.TestRunner()

To prove this on a newly-flashed Feather Huzzah running Micropython 1.9.3, it should be possible (on a posix-compliant platform with adafruit_ampy installed) to cd test/scripts then run ./ to synchronize relevant files to the filesystem of the huzzah, reset the huzzah then connect using screen /dev/ttyUSB0 115200 before running the above commands.

Micropython hosts require a micropython repository alongside the Adafruit_Micropython_Blinka repository. For circuitpython, the repository is expected to be called circuitpython_2.2.3. In each case, the matching version should have been checked out from github and make needs to have been run in the mpy-cross folder. This provides a tool to make bytecode-compiled .mpy versions of all .py files before upload so that tests can be achieved within the limited memory available on many target platforms.


There are reference routines in test/scripts like which execute a selective bytecode-compile to .mpy format and an ampy upload for CircuitPython/Micropython on esp8266, or which selectively bytecode-compiles and synchronizes files with cp to the CIRCUITPY or PYBFLASH disk mount for stm32 and samd21 platforms.