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. After building run:

    tools/bossac_osx -e -w -v -b 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
The current Atmel SAMD implementation only works over 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.