In fact there is a simpler way to do that; all these functions are already implemented in the syscalls.c file provided in projects created by Ac6 System Workbench. The only think you need to provide are the blocking USART read/write routins that should be defined as:

int __io_putchar(int ch) {
    // Code to write character 'ch' on the UART
}

int __io_getchar(void) {
    // Code to read a character from the UART
}

The only thing that was not (yet) done by the provided code s to allow to open several “files” on various devices and write or read from them. For this to work you should just redefine _open, _read and _write, probably by modifying the syscalls.c file, and this will work seamlessly.

Furthermore, if you use some RTOS (like FreeRTOS) you can write your low-level I/O routines to sleep while waiting characters and send output using a buffer and interrupts; probably this would need modifying the _read and _write routines in a quite natural way.

Bernard