FOTB - Firmware Over The Bus

See: https://github.com/arduino/ArduinoCore-samd/pull/220

Steps:

Get SDUBoot.ino from https://github.com/arduino/ArduinoCore-samd/tree/master/libraries/SDU/extras/SDUBoot. Use this as starting point for an own version, let's say we name our version "MyBoot"

So we will have

MyBoot\
MyBoot\EFUBoot.ino

and we also need

MyBoot\boot
MyBoot\build.sh

build.sh should contain something like this:

#!/bin/sh -x

ARDUINO=$ARDUINO_HOME/arduino
SKETCH_NAME="MyBoot.ino"
SKETCH="$PWD/$SKETCH_NAME"
BUILD_PATH="$PWD/build"
OUTPUT_PATH="./boot"

if [[ "$OSTYPE" == "darwin"* ]]; then
	ARDUINO="/Applications/Arduino.app/Contents/MacOS/Arduino"
fi

buildSDUBootSketch() {
	BOARD=$1
	DESTINATION=$2

	$ARDUINO --verify --board $BOARD --preserve-temp-files --pref build.path="$BUILD_PATH" $SKETCH
	cat "$BUILD_PATH/$SKETCH_NAME.bin" | xxd -i > $DESTINATION
	rm -rf "$BUILD_PATH"
}

mkdir -p "$OUTPUT_PATH"

buildSDUBootSketch "arduino:samd:arduino_zero_edbg" "$OUTPUT_PATH/zero.h"

Make it executable with help of

chmod g+x build.sh

And finally run it with

./build.sh

After that, you have a .h file in your boot-folder.