I'm getting an "undefined reference to `__putchar'" error message, what does this mean?
This error indicates that you are using a stdio output function such as printf and that you haven't implemented the __putchar function that is required to actually carry out the output.
As an example, the following code demonstrates an implementation of __putchar that outputs to a UART:
if (ch == '\n')
Note: If all want to do is make the stdio functions output to the debug terminal rather than hardware you should set the Library Options > I/O Library Name project property to debug or, alternatively, use the debug I/O functions directly (for example use debug_printf rather than printf).