This example describes how to make UART communication via UART0

Procedure for UART Interface with Cortex m4

1. Power: In the PCONP register, set bit PCUART0
2. Configure pins P0.2 and P0.3 as UART0 TX and RX using IOCON_P0_2 and IOCON_P0_3.
3. Select Clock source and frequency
4. Set no. of data bits, stop bit, parity and Give access to Baud rate register
5. Derive baud rate from the UART clock source
6. Check the Transmitter flag, If it is High Transmit a character
7. Check the Receiver flag for data ready. If the data is ready Read the character

UART Interface with Cortex m4 -C source code

#include "LPC407x_8x_177x_8x.h"

unsigned char recval=0, welstring[]="Hi: Press a Key\r\n";

unsigned char UART0_Receive(void);
void UART0_Txmt(unsigned char Chr);
void init_serial(void);
void UART0_puts(unsigned char *string);

int main(void)
{
		init_serial();		
		UART0_puts(welstring);
		while(1)
		{
			recval=UART0_Receive();
			UART0_Txmt(recval);
		}
}


void init_serial(void) 
{
		//1. set bit PCUART0 
		LPC_SC->PCONP |= (1 << 3); 										/* enable power to UART0*/

		//2. Configure pins P0.2 and P0.3 as UART0 TX and RX
		LPC_IOCON->P0_2 |=  1;        								/* Pin P0.2 used as TXD0 */
		LPC_IOCON->P0_3 |=  1;        								/* Pin P0.3 used as RXD0 */
		
		//3.Select Clock source and frequency=PCLK ie 30MHz
		/* 8 bits, no Parity, 1 Stop bit   */
		// Set DLAB=1 to access baud rate Register
		LPC_UART0->LCR    = 0x83;   
		
		//4. Derive baud rate from the UART clock source, 
		//DLM:DLL=PCLK/(16*baud)= 30Mhz/(16*9600)= 195	
		LPC_UART0->DLL    = 195;                      /* 9600 Baud Rate @ 30.0 MHZ PCLK*/
		LPC_UART0->DLM    = 0;                        /* MSB = 0 */	
		LPC_UART0->LCR    = 0x03;                     /* DLAB = 0*/
}

//Transmit a character 
void UART0_Txmt(unsigned char Chr)
{
	//6. Check the Transmitter flag
	//   If it is High Transmit a character
		while((LPC_UART0->LSR & 0x20)==0);
		LPC_UART0->THR = Chr; 
}

//Receive a character
unsigned char UART0_Receive(void)
{
		//7.Check the Receiver flag for data ready
		//  and Read the character
		while((LPC_UART0->LSR & 0x01)==0);
		return(LPC_UART0->RBR); 
}

//Transmit a string 
void UART0_puts(unsigned char *string)
{
		while(*string)
		UART0_Txmt(*string++);
}