Sending data using serial task

Hello everybody,
I’m using FreeRTOS with IAR Workbench in a ARM7 device it’s a AT91SAM7S128 chip. I want to read the real time timer and I have to send the value of the timer using the serial function of freeRTOS. My problem is that the value of the real time timer it’s an unsigned int and the serial function allow me to send char value.
So How can I convert unsigned int into char. I’ve tried to use utoa() fonction but it’s not recognized by IAR.
Thank you for your help.

Sending data using serial task

sprintf(buf,”%u”,val);