circuitpython-flash-logger

Basic datalogging to SPI flash memory on Adafruit's CircuitPython Express boards. Currently, only a Feather M0 Express has been tested.

Thanks!

This code is based on super-helpful suggestions by tannewt2 of Adafruit -- thank you for all the help! The good ideas are theirs -- any implementation errors are my fault :)

Requirements

Hardware: This particular setup requires using a simple switch to toggle the state of an IO pin on the board. A through-hole 10K resistor can be used for this purpose.

Software: This firmware requires that a recent version of the circuitpython UF2 master branch, which allows for filesystem remount via storage.remount(), be installed. Instructions below for how to do this for the Feather M0 Express board.

Installation (Feather M0 Express)

(All code below comes from the "feather_m0_express" directory in this github repo.)

1. Connect the microcontroller to your laptop.

• Plug the Feather M0 Express into a USB port. A USB drive will appear as CIRCUITPY. Ignore this for now.

2. Install the UF2

• Double-press the reset button in order to enter into bootloader mode. A USB drive will appear on your desktop as "FEATHERBOOT".
• Copy the .uf2 file into FEATHERBOOT.

3. Install the firmware

• Now single-press the reset button. A USB drive will appear on your desktop as "CIRCUITPY".
• Copy "boot.py" and "code.py" into CIRCUITPY.

Usage (Feather M0 Express)

• Datalogging. Connect a 10K resistor between pin D6 and 3V (pulling D6 "high"), and single-press the RESET button in order to reset the board. The microcontroller will boot up in "datalogging mode", and write values to a file called "data.txt" on the on-board SPI flash chip at one second intervals, flashing the red on-board LED after each write. In this mode, write access to the SPI Flash via USB is disabled -- i.e., CIRCUITPY mounts in "read-only" mode.

• Reprogramming. When D6 is not pulled "high" (no connector / resistor between D6 and 3V), the microcontroller will simply flash the on-board LED at 0.2 second intervals, and CIRCUITPY mounts in "write-allowed" mode. This allows for new boot.py and code.py code to be uploaded to the board via drag-drop.