UART0 (ttyAMA0) Serial Port Configuration
ttyAMA0 is the main Raspberry Pi serial port for communication with peripherals, it is routed to both the HAT connector and the MyPi ASIO connector on the pins below.
The ASIO Connector brings both pins 14-17 and 30-33 out, the default UART0 configuration overlays work with pins 30-33
To enable the UART you need to compile/copy the device tree overlay files to the /boot/overlays folder
Next we need edit/add the below lines in /boot/config.txt to enable either just the basic RX/TX lines or the full set including flow control (RX/TX/RTS/CTS)
You can cross check these lines have been correctly configured by using raspi-gpio get