Defining macro to change print function error due to argument difference - c

Question

I'm trying to use unity testing framework with an NRF51822 board, but in order to see the output from unity i need to reroute it / pipe so its visible on my coumputer. I am using SEGGER RTT to print in my porject and ideally id use the same for unity.c output.
According to unity
By default, Unity prints its results to stdout as it runs. This
works perfectly fine in most situations where you are using a native
compiler for testing. It works on some simulators as well so long as
they have stdout routed back to the command line. There are times,
however, where the simulator will lack support for dumping results or
you will want to route results elsewhere for other reasons. In these
cases, you should define the UNITY_OUTPUT_CHAR macro. This macro
accepts a single character at a time (as an int, since this is the
parameter type of the standard C putchar function most commonly
used). You may replace this with whatever function call you like.
* Output* - by default, Unity prints to standard out with putchar. define UNITY_OUTPUT_CHAR(a) with a different function if
desired
/*-------------------------------------------------------
* Output Method: stdout (DEFAULT)
*-------------------------------------------------------*/
#ifndef UNITY_OUTPUT_CHAR
/* Default to using putchar, which is defined in stdio.h */
#include <stdio.h>
#define UNITY_OUTPUT_CHAR(a) (void)putchar(a)
#else
/* If defined as something else, make sure we declare it here so it's ready for use */
#ifndef UNITY_OMIT_OUTPUT_CHAR_HEADER_DECLARATION
extern void UNITY_OUTPUT_CHAR(int);
#endif
#endif
I tried to define
#define UNITY_OUTPUT_CHAR(a) SEGGER_RTT_WriteString(0, a)
However i get the following
> $ make rm -rf _build echo Makefile Makefile mkdir _build Compiling
> file: system_nrf51.c Compiling file: main.c
> C:/NXTSNS/nRF5_SDK_11.0.0_89a8197/examples/peripheral/blinky/main.c:31:53:
> error: expected declaration specifiers or '...' before numeric
> constant
> #define UNITY_OUTPUT_CHAR(a) SEGGER_RTT_WriteString(0, a)
> ^ C:/NXTSNS/Unittesting/unity/src/unity_internals.h:250:13: note: in
> expansion of macro 'UNITY_OUTPUT_CHAR' extern void
> UNITY_OUTPUT_CHAR(int);
> ^ Makefile:150: recipe for target '_build/main.o' failed make: *** [_build/main.o] Error 1
I also tried this alternative of calling segger in a function and casting to char * as follows
void print_test(int a){
SEGGER_RTT_WriteString(0, (char *) a);
}
but unfortuneatly i dont see any output when i call print_test
How should i define the macro such that i can send the output to segger or if there is a more suitable alternative what is it?