Mini ARM Board-LPC2148

/*
*    PIN CONNECTION    :
*    LED            ->        0.0
*    BUTTON1    ->        0.1
*    BUTTON2    ->        0.2
*    BUTTON3    ->        0.3
*    BUTTON4    ->        0.4
*/
#include <lpc214x.h>

#define PLOCK 0x00000400
#define PWMPRESCALE 60   //60 PCLK cycles to increment TC by 1 i.e 1 Micro-second

void initPWM(void);

void initClocks(void);
void setupPLL0(void);
void feedSeq(void);
void connectPLL0(void);

int main(void)
{
    initClocks(); //Initialize CPU and Peripheral Clocks @ 60Mhz
    initPWM(); //Initialize PWM

  //IO0DIR = 0x1; This is not needed!
    //Also by default all pins are configured as Inputs after MCU Reset.
    IO0DIR = 0x01;
   
    while(1)
    {
        if( ((IO0PIN) & (1<<1)) ) // Check P0.1
        {
            PWMMR1 = 2500; //T-ON=25% , Hence 25% Bright
            PWMLER = (1<<1); //Update Latch Enable bit for PWMMR1
        }
        else if( ((IO0PIN) & (1<<2)) ) // Check P0.2
        {
            PWMMR1 = 5000; //50% Bright
            PWMLER = (1<<1);
        }
        else if( ((IO0PIN) & (1<<3)) ) // Check P0.3
        {
            PWMMR1 = 7500; //75% Bright
            PWMLER = (1<<1);
        }
        else if( ((IO0PIN) & (1<<4)) ) // Check P0.4
        {
            PWMMR1 = 10000; //100% Bright
            PWMLER = (1<<1);
        }
    }
    //return 0; //normally this wont execute ever
}

void initPWM(void)
{
    /*Assuming that PLL0 has been setup with CCLK = 60Mhz and PCLK also = 60Mhz.*/
    /*This is a per the Setup & Init Sequence given in the tutorial*/

    PINSEL0 = (1<<1); // Select PWM1 output for Pin0.0
    PWMPCR = 0x0; //Select Single Edge PWM - by default its single Edged so this line can be removed
    PWMPR = PWMPRESCALE-1; // 1 micro-second resolution
    PWMMR0 = 10000; // 10ms period duration
    PWMMR1 = 2500; // 2.5ms - pulse duration i.e width (Brigtness level)
    PWMMCR = (1<<1); // Reset PWMTC on PWMMR0 match
    PWMLER = (1<<1) | (1<<0); // update MR0 and MR1
    PWMPCR = (1<<9); // enable PWM output
    PWMTCR = (1<<1) ; //Reset PWM TC & PR

    //Now , the final moment - enable everything
    PWMTCR = (1<<0) | (1<<3); // enable counters and PWM Mode

    //PWM Generation goes active now - LED must be 25% Bright after boot!!
    //Now you can get the PWM output at Pin P0.0!
}


void initClocks(void)
{
    setupPLL0();
    feedSeq(); //sequence for locking PLL to desired freq.
    connectPLL0();
    feedSeq(); //sequence for connecting the PLL as system clock
   
    //SysClock is now ticking @ 60Mhz!
       
    VPBDIV = 0x01; // PCLK is same as CCLK i.e 60Mhz
   
    //Using PLL settings as shown in : http://www.ocfreaks.com/lpc214x-pll-tutorial-for-cpu-and-peripheral-clock/
    //PLL0 Now configured!
}


//---------PLL Related Functions :---------------

void setupPLL0(void)
{
    //Note : Assuming 12Mhz Xtal is connected to LPC2148.
   
    PLL0CON = 0x01; // PPLE=1 & PPLC=0 so it will be enabled
                    // but not connected after FEED sequence
    PLL0CFG = 0x24; // set the multipler to 5 (i.e actually 4)
                    // i.e 12x5 = 60 Mhz (M - 1 = 4)!!!
                    // Set P=2 since we want FCCO in range!!!
                    // So , Assign PSEL =01 in PLL0CFG as per the table.
}

void feedSeq(void)
{
    PLL0FEED = 0xAA;
    PLL0FEED = 0x55;
}

void connectPLL0(void)
{
    // check whether PLL has locked on to the  desired freq by reading the lock bit
    // in the PPL0STAT register

    while( !( PLL0STAT & PLOCK ));

    // now enable(again) and connect
    PLL0CON = 0x03;
}