Purpose
===================================
This directory contains modifications required to build the
bootloader for the sinker-camera-controller (SCC) board that
is based on the Moteino M0.

The bootloader used on the SCC board is from Arduino Core for SAMD.
The source repo can found here: https://github.com/arduino/ArduinoCore-samd
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Modifications
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For the SCC it is necessary to specify that the board is 'crystalless'
when building the bootloader. The board does not use an external
crystal to drive the processor (an internal crystal is used).

To achieve this the header file
'ArduinoCore-samd-master/bootloaders/zero/board_definitions_arduino_zero.h'
contains a line to define the symbol 'CRYSTALLESS':

#define CRYSTALLESS  (1)
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Associated topics
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To take advantage of the CRYSTALLESS option in the bootloader, it is also
necessary to build the SCC application using the compliation flag:

-D CRYSTALLESS

In our case, this was accomplished by adding a new line to the
platformio.ini configuration file for this project:

build_flags = -D CRYSTALLESS
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