File content as of revision 1:4e19f154ec21:

#include "SCT_PWM.h"

#define BIT_ON(A) (1<<A)

// http://www.lpcware.com/content/nxpfile/lpc80-sct-cookbook-and-tutorial-code-examples

SCT_PWM::SCT_PWM(int pin, int channel) : ch(channel)
{
    static bool insted = false;

    if (!insted) {
        inst();
        insted = true;
    }
    swm(pin);

    LPC_SCT->EVENT[ch + 1].STATE = LPC_SCT->EVENT[0].STATE;
    LPC_SCT->EVENT[ch + 1].CTRL = LPC_SCT->EVENT[0].CTRL | (ch+1)<<0; // match 1...5

    LPC_SCT->OUT[ch].SET = BIT_ON(0); // event 0
    LPC_SCT->OUT[ch].CLR = BIT_ON(ch+1); // event 1...5
}

void SCT_PWM::inst()
{
    LPC_SYSCON->SYSAHBCLKCTRL |= (1<<8); // enable SCT
    LPC_SYSCON->PRESETCTRL |= (1<<8); // reset SCT

    LPC_SCT->EVENT[0].STATE = BIT_ON(0); // state 0
    LPC_SCT->EVENT[0].CTRL = (1<<12) | (1<<14);

    LPC_SCT->LIMIT_L |= BIT_ON(0); // event 0

    LPC_SCT->CONFIG |= (1<<0) | (1<<17); // unify, auto limit
    LPC_SCT->CTRL_L |= (SystemCoreClock/1000000-1)<<5; // set prescaler, SCT clock = 1 MHz

    LPC_SCT->CTRL_L &= ~(1<<2); // unhalt it by clearing bit 2 of CTRL reg
}

void SCT_PWM::swm(int pin)
{
    switch(ch) {
        case 0: // CTOUT_0
            LPC_SWM->PINASSIGN6 = (LPC_SWM->PINASSIGN6 & 0x00ffffff) | pin<<24;
            break;
        case 1: // CTOUT_1
            LPC_SWM->PINASSIGN7 = (LPC_SWM->PINASSIGN7 & 0xffffff00) | pin<<0;
            break;
        case 2: // CTOUT_2
            LPC_SWM->PINASSIGN7 = (LPC_SWM->PINASSIGN7 & 0xffff00ff) | pin<<8;
            break;
        case 3: // CTOUT_3
            LPC_SWM->PINASSIGN7 = (LPC_SWM->PINASSIGN7 & 0xff00ffff) | pin<<16;
            break;
    }
}

void SCT_PWM::period(float seconds)
{
    period_us(seconds * 1000000);
}

void SCT_PWM::period_ms(int ms)
{
    period_us(ms * 1000);
}

void SCT_PWM::period_us(int us)
{
    LPC_SCT->MATCHREL[0].U = us - 1;
}

void SCT_PWM::pulsewidth(float seconds)
{
    pulsewidth_us(seconds * 1000000);
}

void SCT_PWM::pulsewidth_ms(int ms)
{
    pulsewidth_us(ms * 1000);
}

void SCT_PWM::pulsewidth_us(int us)
{
    LPC_SCT->MATCHREL[ch + 1].U = us;
}

void SCT_PWM::write(float value)
{
    LPC_SCT->MATCHREL[ch + 1].U = value * LPC_SCT->MATCHREL[0].U;
}

float SCT_PWM::read()
{
    if (LPC_SCT->MATCHREL[0].U == 0) {
        return 0.0;
    }
    return (float)LPC_SCT->MATCHREL[ch + 1].U / LPC_SCT->MATCHREL[0].U;
}