circuitpython/atmel-samd/README.md

# SAMD21x18

This port is intended to be a full featured MicroPython port for SAMD21x18 based
development boards including the Arduino Zero, Adafruit Feather M0 and Adafruit
M0 BLE.

## Building

The Makefile has the ability to build for a SAMD21x18, and by default
includes some start-up code and also enables a UART for communication.  To
build:

    make CROSS=1

It will build for the Arduino Zero by default. You may change it by setting
`BOARD`. For example:

    make CROSS=1 BOARD=feather_m0_ble

Board names are the directory names in the `boards` folder.

## Deploying

### Arduino Bootloader
If your board has an existing Arduino bootloader on it then you can use bossac
to flash MicroPython. First, activate the bootloader. On Adafruit Feathers you
can double click the reset button and the #13 will fade in and out. Finally,
run bossac:

    tools/bossac_osx -e -w -v -b -R build-feather_m0_ble/firmware.bin

### No Bootloader via GDB
This method works for loading MicroPython onto the Arduino Zero via the
programming port rather than the native USB port.

Note: These instructions are tested on Mac OSX and will vary for different
platforms.

    openocd -f ~/Library/Arduino15/packages/arduino/hardware/samd/1.6.6/variants/arduino_zero/openocd_scripts/arduino_zero.cfg

In another terminal from `micropython/atmel-samd`:

    arm-none-eabi-gdb build-arduino_zero/firmware.elf
    (gdb) tar ext :3333
    ...
    (gdb) load
    ...
    (gdb) monitor reset init
    ...
    (gdb) continue

## Connecting
All boards are currently configured to work over USB rather than UART. To
connect to it from OSX do something like this:

    screen /dev/tty.usbmodem142422 115200

You may not see a prompt immediately because it doesn't know you connected. To
get one either hit enter to get `>>>` or do CTRL-B to get the full header.