Raspberry pi offers two UARTS:
- PL011 UART: offers the 5bits mode required 
- Mini UART:  do not offer that mode

So, PL011 UART SHOULD BE USED and CONFIGURED in order to run the software.

By default, on most RaspPIs, PL011 is selected and connected on GP14 and GP15
The related driver '/dev/ttyAMAP0' is also linked to the driver '/dev/serial0'

However, RaspPIs offering a BT module make use of the PL011 for thise device.
So, in order to work, these modules do have to be disabled and an external USB
BT module has to be used for BT communications...

This UART dont support the 1.5 stop bits mode so the 1 stop mode has to be
configured. BUT it may support 45.5, 50 and 75 bauds rates !

From the BCM2835 ARM peripheral datasheet
- Fully-programmable serial interface characteristics: 
- data can be 5, 6, 7, or 8 bits 
- even, odd, stick, or no-parity bit generation and detection 
- 1 or 2 stop bit generation 
- baud rate generation, dc up to UARTCLK/16 

