#include "LPC17xx.h"

unsigned long int duty_cycle = 0;
int direction = 1;
int step = 50;

void PWM1_IRQHandler(void)
{
    if (LPC_PWM1->IR & (1 << 0))
    {
        if (direction == 1)
        {
            duty_cycle += step;
            if (duty_cycle >= 3000)
            {
                duty_cycle = 3000;
                direction = 0;
            }
        }
        else
        {
            duty_cycle -= step;
            if (duty_cycle <= 0)
            {
                duty_cycle = 0;
                direction = 1;
            }
        }

        LPC_PWM1->MR4 = duty_cycle;
        LPC_PWM1->LER = (1 << 4);
        LPC_PWM1->IR = (1 << 0);
    }
}

int main(void)
{
    LPC_PINCON->PINSEL3 |= (2 << 14);

    LPC_PWM1->TCR = (1 << 1);
    LPC_PWM1->CTCR = 0;
    LPC_PWM1->PR = 0;

    LPC_PWM1->MR0 = 3000;
    LPC_PWM1->MR4 = duty_cycle;

    LPC_PWM1->MCR = (1 << 1) | (1 << 0);
    LPC_PWM1->PCR = (1 << 12);

    LPC_PWM1->LER = (1 << 0) | (1 << 4);

    NVIC_EnableIRQ(PWM1_IRQn);

    LPC_PWM1->TCR = (1 << 0) | (1 << 3);

    while (1);
}