VESC custom firmware custom UART message

Hello everyone, currently I'm trying to build a custom firmware that the goal is to achieve a custom UART message exchange function.

However, I am abit new to the ChibiOS and the VESC firmware, for now I tried few UART functions, e.g.:

sdPut(&SD2,'A');

sdWrite(&SD2, "hello", 8);

to send custom message from VESC to external devices, but no luck.  

The Eclipse compiler sometimes shows error:  note: in expansion of macro 'sdPut'

Any suggestions that how to properly initialize the RX TX port on the VESC ?

I have configured the baudrate and hookup the RXTX port to a external UART Assistant monitor hardware software.

Thanks!