circuitpython-adxl36x

CircuitPython driver for the Analog Devices ADXL366 and ADXL367 ultra-low-power 3-axis MEMS accelerometers.

ADXL367 implements the full shared register map and is the base class. ADXL366 subclasses it, adding the pedometer, Z-axis nonlinearity compensation, and activity/inactivity reference readback - the three features the ADXL367 silicon doesn't implement. Both support SPI and I2C.

Relationship to adafruit_adxl34x

This library's public API deliberately mirrors the shape of Adafruit's adafruit_adxl34x driver for the ADXL34x family (.acceleration, .events, enable_tap_detection(), enable_motion_detection(), data_rate) so that code written against a 34x-family chip needs minimal changes to run against a 366/367. The two chip families are not register-compatible — only the driver's Python API shape is shared. Notable differences:

• range is named g_range here instead — range shadows the Python builtin, and compatibility with the ADXL34x API takes a back seat to that on this one property.
• No enable_freefall_detection() — the 366/367 has no freefall-detection hardware.
• Range tops out at RANGE_8_G — the 366/367 doesn't support ±16g.
• DataRate only has 6 discrete rates (12.5 Hz-400 Hz) vs. the 34x's 16.
• .events includes many more keys (FIFO, pedometer, ADC/temperature thresholds) since the 366/367 exposes far more interrupt sources.

Supported features

✅ Supported    🚫 Not present on this chip    🚧 Not yet supported by this driver

Free fall isn't a separate feature/method - it's a documented usage pattern of absolute (non-referenced) inactivity detection (enable_inactivity_detection(referenced=False)), already fully supported.

The 🚧 rows are real hardware features (confirmed present on both chips, same register addresses, per each chip's own datasheet) that this driver doesn't expose yet - they need either extra wiring/signal sources not on the current breadboard (external ADC input, external clock, external trigger) or aren't yet confirmed as needed by any downstream project (noise modes). Contributions welcome.

Installation

On a CircuitPython board, copy src/adxl36x/ into CIRCUITPY/lib/adxl36x/. No other bundle libraries are required - this driver talks to busio.I2C/busio.SPI directly.

For boards tight on RAM/flash, or if raw source ever fails to compile on-device, each GitHub release also attaches a precompiled .mpy bundle (lib/adxl36x/__init__.mpy) - unzip it and copy lib/adxl36x/ into CIRCUITPY/lib/ instead. It's compatible with any CircuitPython release sharing the same .mpy bytecode version (stable across CircuitPython 9.0.0+ as of this writing) - not just the exact version it was built against.

For host-side development (type checking, tests) in another project:

uv add --editable ~/src/circuitpython-adxl36x

Hardware validation setup

The examples/hw_*.py scripts and examples/hw_checks.py exercise real silicon and are set up to run against a doit_esp32_devkit_v1 board wired to an EVAL-ADXL366Z breakout, over either I2C or SPI:

I2C (hw_sanity_check.py / hw_interactive_check.py - edit their board.I2C() call to busio.I2C(board.D26, board.D33) to match these pins):

The EVAL-ADXL366Z has no onboard I2C pull-ups - add external 4.7kOhm pull-ups from SDA and SCL to 3.3V.

SPI (hw_spi_sanity_check.py / hw_spi_interactive_check.py):

INT1/INT2 are only needed for the interactive checks (motion/inactivity/tap interrupts, autosleep wake cycle, orientation, pedometer) - the non-interactive sanity checks only need the data bus.

Development

uv sync
uv run ruff check --fix
uv run ruff format
uv run ty check
uv run pytest