Configure the UART in MCC

Once you Geneate the MCC code it will have dealt with initialising the UART ready for you to use it.

In your code

#include <definitions.h>			//Include all the MCC generated files so their fucntions can be called

volatile uint8_t Uart3RxBuffer[1];


//IN YOUR INITIALSE CODE
	//----- SETUP USART 3 -----
	//Used for: 
	//Config done in MCC:
	//	Setup IO pin assignments:
	//		PPS Input Pin Configuration > Use PPS Input# > U3RX, > RPF0
	//		PPS Output Pin Configuration > Use PPS Output# > U3TX > RPF1
	//	Setup UART:
	//		Operating mode: None blocking mode
	//		115200-8-N-1
	//	Setup interrupts:
	//		Enable UART1 Fault Interrupt = Will already be set to Yes
	//		Enable UART1 Receive Done Interrupt = Will already be set to Yes
	//		Enable UART1 Transmit Done Interrupt = Will already be set to Yes
	//		Priority (set for all): 3	//<<<Set as required for your application
	//		Subpriority (set for all): 0	//<<<Set as required for your application

	//UART3_WriteCallbackRegister(UART3_MyTxEventHandler, (uintptr_t)NULL);		//Register our callback function to be called when TX is complete (optional)
	UART3_ReadCallbackRegister(UART3_MyRxEventHandler, (uintptr_t)NULL);		//Register our callback function to be called when data is received or a RX error occurs

	//Start receiving
	UART3_Read(&Uart3RxBuffer[0], 1);			//You can setup to receive multiple bytes, but we want an IRQ callback to us for every byte received

	//TX some bytes
	uint8_t TxBuffer[] = {0x30, 0x39};
	UART3_Write(&TxBuffer[0], sizeof(TxBuffer));

//YOUR FUNCTION TO BE CALLED WHEN TX IS COMPLETE (if wanted)
//*******************************************
//*******************************************
//********** UART3 TX COMPLETE IRQ **********
//*******************************************
//*******************************************
/*
void UART3_MyTxEventHandler(uintptr_t context)
{
	//TX HAS COMPLETED
	
}
*/

//YOUR FUNCTION TO BE CALLED WHEN RX IS COMPLETE
//**********************************
//**********************************
//********** UART3 RX IRQ **********
//**********************************
//**********************************
void UART3_MyRxEventHandler(uintptr_t context)
{
	uint8_t Data;
	
	Data = Uart3RxBuffer[0];
	
	if (UART3_ErrorGet() != UART_ERROR_NONE)
	{
		//A RX ERROR HAS OCCURED
		//(It has been cleared already)
		
		//UART_ERROR Values: UART_ERROR_NONE, UART_ERROR_OVERRUN, UART_ERROR_FRAMING, UART_ERROR_PARITY
		
		//Start receiving again ready for next byte
		UART3_Read(&Uart3RxBuffer[0], 1);
	}
	else
	{
		//WE HAVE A VALID RX 
		
		//Start receiving again ready for next byte
		UART3_Read(&Uart3RxBuffer[0], 1);
		
				
		//>>>>> Test code - return the byte + 1
		//U3TXREG = Data + 1;
		//<<<<<
		
	}
}

Other UART functions

MCC will have created a few useful functions you can call – see the file it generated in: /config/default/peripheral/uart/