lpc1768_uartExample1.c

#include <lpc17xx.h>
#include "stdutils.h"

#define SBIT_WordLenght    0x00u
#define SBIT_DLAB          0x07u
#define SBIT_FIFO          0x00u
#define SBIT_RxFIFO        0x01u
#define SBIT_TxFIFO        0x02u

#define SBIT_RDR           0x00u
#define SBIT_THRE          0x05u



/* Function to initialize the UART0 at specifief baud rate */
void uart_init(uint32_t baudrate)
{
    uint32_t var_UartPclk_u32,var_Pclk_u32,var_RegValue_u32;

    LPC_PINCON->PINSEL0 &= ~0x000000F0;
    LPC_PINCON->PINSEL0 |= 0x00000050;            // Enable TxD0 P0.2 and p0.3 

    LPC_UART0->FCR = (1<<SBIT_FIFO) | (1<<SBIT_RxFIFO) | (1<<SBIT_TxFIFO); // Enable FIFO and reset Rx/Tx FIFO buffers    
    LPC_UART0->LCR = (0x03<<SBIT_WordLenght) | (1<<SBIT_DLAB);             // 8bit data, 1Stop bit, No parity


    /** Baud Rate Calculation :
       PCLKSELx registers contains the PCLK info for all the clock dependent peripherals.
       Bit6,Bit7 contains the Uart Clock(ie.UART_PCLK) information.
       The UART_PCLK and the actual Peripheral Clock(PCLK) is calculated as below.
       (Refer data sheet for more info)

       UART_PCLK    PCLK
         0x00       SystemFreq/4        
         0x01       SystemFreq
         0x02       SystemFreq/2
         0x03       SystemFreq/8   
     **/

    var_UartPclk_u32 = (LPC_SC->PCLKSEL0 >> 6) & 0x03;

    switch( var_UartPclk_u32 )
    {
    case 0x00:
        var_Pclk_u32 = SystemCoreClock/4;
        break;
    case 0x01:
        var_Pclk_u32 = SystemCoreClock;
        break; 
    case 0x02:
        var_Pclk_u32 = SystemCoreClock/2;
        break; 
    case 0x03:
        var_Pclk_u32 = SystemCoreClock/8;
        break;
    }


    var_RegValue_u32 = ( var_Pclk_u32 / (16 * baudrate )); 
    LPC_UART0->DLL =  var_RegValue_u32 & 0xFF;
    LPC_UART0->DLM = (var_RegValue_u32 >> 0x08) & 0xFF;

    util_BitClear(LPC_UART0->LCR,(SBIT_DLAB));  // Clear DLAB after setting DLL,DLM
}


/* Function to transmit a char */
void uart_TxChar(char ch)
{
    while(util_IsBitCleared(LPC_UART0->LSR,SBIT_THRE)); // Wait for Previous transmission
    LPC_UART0->THR=ch;                                  // Load the data to be transmitted
}


/* Function to Receive a char */
char uart_RxChar()
{
    char ch; 
    while(util_IsBitCleared(LPC_UART0->LSR,SBIT_RDR));  // Wait till the data is received
    ch = LPC_UART0->RBR;                                // Read received data    
    return ch;
}



int main()
{
    char ch,a[]="\n\rExploreEmbedded";
    int i;

    SystemInit();
    uart_init(9600);  // Initialize the UART0 for 9600 baud rate

    uart_TxChar('h'); //Transmit "hello" char by char
    uart_TxChar('e');
    uart_TxChar('l');
    uart_TxChar('l');
    uart_TxChar('o');


    for(i=0;a[i];i++)  //transmit a predefined string
        uart_TxChar(a[i]);


    while(1)
    {
        //Finally receive a char and transmit it infinitely
        ch = uart_RxChar(); 
        uart_TxChar(ch);
    }       
}