main.c

/*******************************************************************************
 *
 *      Author:		Austin Schaller
 *	Module:		uart.c
 *	Description:	Library functions that permit utilization of LPC17xx
 *			UART0 peripheral.
 *	Documentation:	"UART - TLD"
 *
*******************************************************************************/

#ifdef __USE_CMSIS
#include "LPC17xx.h"
#endif

#include <cr_section_macros.h>
#include <NXP/crp.h>


/*
 * Variable to store CRP value in. Will be placed automatically
 * by the linker when "Enable Code Read Protect selected.
 * See crp.h header for more information.
 */
__CRP const unsigned int CRP_WORD = CRP_NO_CRP ;


#include <stdio.h>

#include "uart.h"
#include "timer.h"


int main(void)
{
	set_u0pclk(UART0_PCLK);		// UART_PCLK = 120 MHz
	init_uart0(BAUD_RATE);		// Baud Rate of 57600
	
	printf("Hello World!");
	
	return 0;
}

uart.c

/*******************************************************************************
 *
 *      Author:		Austin Schaller
 *	Module:		uart.c
 *	Description:	Library functions that permit utilization of LPC17xx
 *			UART0 peripheral.
 *	Documentation:	"UART - TLD"
 *
*******************************************************************************/

/** Include Files *************************************************************/
#include "LPC17xx.h"
#include "system_LPC17xx.h"

#include "uart.h"


/** Defines *******************************************************************/
#define IER_RBR		0x01
#define IER_THRE	0x02
#define IER_RLS		0x04

#define IIR_PEND	0x01
#define IIR_RLS		0x03
#define IIR_RDA		0x02
#define IIR_CTI		0x06
#define IIR_THRE	0x01

#define LSR_RDR		0x01
#define LSR_OE		0x02
#define LSR_PE		0x04
#define LSR_FE		0x08
#define LSR_BI		0x10
#define LSR_THRE	0x20
#define LSR_TEMT	0x40
#define LSR_RXFE	0x80


static uint32_t get_u0pclk(void)
{
    uint32_t u0pclk_div = (LPC_SC->PCLKSEL0 >> 8) & 0x03;

    switch(u0pclk_div)
    {
    	case 0x00:
    	    return SystemCoreClock/4.0;
    	case 0x01:
    	    return SystemCoreClock;
    	case 0x02:
    	    return SystemCoreClock/2.0;
    	case 0x03:
    	    return SystemCoreClock/8.0;

    }

    return (SystemCoreClock/u0pclk_div);
}


static void set_u0pclk(uint8_t bit_val)
{
    uint32_t regVal;

    regVal = LPC_SC->PCLKSEL0;
    regVal |= ((bit_val << 6) & 0xFF);       // UART0
}


void UART0_SendChar(char c)
{
    while((LPC_UART0->LSR & LSR_THRE) == 0);	// Wait until TX is empty
    LPC_UART0->THR = c;
}


char UART0_GetChar(void)
{
    char c;
    while((LPC_UART0->LSR & LSR_RDR) == 0);  // Nothing received so just block
    c = LPC_UART0->RBR; // Read Rx buffer register
    return c;
}

void UART0_print(char *p_string)
{
    int i = 0;
    while(p_string[i] != '\0')
    {
        UART0_SendChar(p_string[i]);
        i++;
    }
}


void init_uart0(uint32_t baud_rate)
{
    uint64_t Fdiv;

    LPC_SC->PCONP |=  (1 << 3);      // Power UART0

    set_u0pclk(UART0_PCLK);

    // Set PINSEL0 so that P0.2 = TXD0, P0.3 = RXD0
    LPC_PINCON->PINSEL0 &= ~0xF0;
    LPC_PINCON->PINSEL0 |= ((1 << 4) | (1 << 6));

    LPC_UART0->LCR = 0x83;		// 8 bits, no Parity, 1 Stop bit, DLAB=1

    Fdiv = (get_u0pclk()/16)/baud_rate;
    LPC_UART0->DLM = Fdiv / 256;
    LPC_UART0->DLL = Fdiv % 256;
    LPC_UART0->LCR = 0x03;		// 8 bits, no Parity, 1 Stop bit DLAB = 0
    LPC_UART0->FCR = 0x07;		// Enable and reset TX and RX FIFO
}

uart.h

/*******************************************************************************
 *
 *      Author:		Austin Schaller
 *	Module:		uart.h
 *	Description:	UART0 library for the LPC17xx ARM microprocessor.
 *	Documentation: 	"UART - TLD"
 *
*******************************************************************************/

#ifndef     UART_H
#define     UART_H

/** Defines *******************************************************************/
#define     UART0_PCLK      0x01        // Equal to CCLK
#define     BAUD_RATE       57600


/** Functions *****************************************************************/
static void set_u0pclk(uint8_t bit_val);
void UART0_SendChar(char c);
char UART0_GetChar(void);
void UART0_print(char *p_string);
void init_uart0(uint32_t baud_rate);


#endif // UART_H

uart_io.c

/*******************************************************************************
 *
 *      Author:		Austin Schaller
 *	Module:		uart_io.c
 *	Description:	Configures UART0 peripheral to utilize "printf".
 *	Documentation:	"UART - TLD"
 *
*******************************************************************************/


/** Include Files *************************************************************/
#include <stdio.h>
#include <stdint.h>

#include "uart.h"


#if (__REDLIB_INTERFACE_VERSION__ >= 20000)
    // We are using new Redlib_v2 semihosting interface
    #define WRITEFUNC       __sys_write
#else
    // We are using original Redlib semihosting interface
    #define WRITEFUNC       __write
#endif


int WRITEFUNC(int iFileHandle, char *p_string, int iLen)
{
    uint32_t i;
    for (i = 0; i < iLen; i++)
        UART0_SendChar(p_string[i]); // print each character
    return iLen;
}