Currently port usage is hard-coded to the default port layout, cli
commands are coming in a future commit.
This decouples all code from the global 'serialPorts' structure which
has been removed. Any code that needs to use a serial port can use
findOpenSerialPort() and openSerialPort() and maintain it's own
reference to the port.
Ports can switch between functions. e.g. by default
cli/msp/telemetry/gps
passthrough all use USART1. Each port maintains it's current function.
see begin/endSerialPortFunction.
There are only certain combinations of serial port functions that are
supported, these are listed in serialPortFunctionScenario_e.
This commit also adds a few 'static' keywords to variables that should
have been.
There a a few other minor fixes and tweaks to various bits of code that
this uncovered too.
Since it uses DMA to receive it means that serialRx is broken because
the RX callback function is only used when DMA is NOT used.
Currently only serialRx uses USART callbacks.
Attempting to disable RX DMA didn't work, the USART2 IRQ handler is
never called.
The STM32F3DISCOVERY board would crash when setting GPIOA Pin_13 or
Pin_14 to analog mode so they are excluded in the gpio initialisation.
The USART GPIO configuration did not work when using the F10x code. The
USART status and DMA registers are different too.
