Tiny async serial port C++ library for Arduino Due with 9th bit support

The library supports Arduino Due based on SAM3x8e. Also version for Arduino Mega is provided, but it can be outdated. Everything below are regarded to Arduino Due and applicable for Mega in most. Exceptions for Arduino Mega are noted explicilty.

Patch

Before start using it's necessary to apply patch to the arduino variant.h and variant.cpp files. Assume line below is executed within location of these files.

patch -p1 < variant.patch

For Arduino Mega patch is not provided. It's likely necessary to exclude HardwareSerial*.cpp from being compiled.

Preprocessor definitions

Port numbering complies to Arduino library. To make ports avaiable it's necessary to define these. By default 8 bit variant is provided.

TINY_HAS_HWSERIAL0 TINY_HAS_HWSERIAL1 TINY_HAS_HWSERIAL2 TINY_HAS_HWSERIAL3

It's recommeded to define them within compiler command line by using -D switch like -DTINY_HAS_HWSERIAL1. For 9nth bit support use this -DTINY_HAS_HWSERIAL1=9.

Also we provide "Serial 0" support for Arduino Due. Actually MCU port and Arduino port numbers don't match. Table below describes mappings between these.

Arduino	Tiny	SAM3x8e
Serial1	serial1	USART0
Serial2	serial2	USART1
Serail3	serial3	USART3
Not provided, pins TXD - 11, RXD - 52	serial0	USART2, pins: TXD - PB20, RXD - PB21

Before use serail0 it's necessary to explicilty call init_serial0(). It's made intentionally to avoid accidental configuration override of pins used by port.

To designate in/out buffer queue size to be used by ports define TINY_SERIAL_DEF_BUF_SIZE, defaulted to 32 for Due and 16 for Mega.

Usage

#include <tiny/serial/uart.hpp>

using tiny::io::serial1; 
using tiny::io::extended_port_traits;

...
serial1().open(19200, extended_port_traits::_9n1);

...
while (serial1().available())
{
  const auto octet = serial1().async_read();
  ...
}

9nth bit version operates with unsinged short int type.

Tests

cd tiny
mkdir test-build && cd test-build
cmake ../test 
make && ctest

Serial port mock is provided via #include <tiny/serial.hpp>.