You would not use printf to just send data through the USART. You should use the interface defined by Harmony (Page 1295). If you are looking to send something akin to debug messages, there is a debugger console that is supported that uses the SYS_MESSAGE() function which might be similar enough. There is an example harmony project for using it

You would not use printf to just send data through the USART. You should use the interface defined by Harmony (Page 1295). If you are looking to send something akin to debug messages, there is a debugger console that is supported that uses the SYS_MESSAGE() function which might be similar enough. There is an example harmony project that demonstrates how to use it (located at microchip\harmony\v2_05\apps\examples\system\debug_uart\firmware\src)