#include "LPC17xx.h"

volatile unsigned long int duty_cycle = 300;
volatile unsigned long int pwm_counter = 0;

#define LED_MASK            (0xFF << 4)

#define COL0                (1<<0)
#define COL1                (1<<1)
#define COL2                (1<<23)
#define COL3                (1<<24)
#define ROW0                (1<<25)

#define COL_MASK_P0         (COL2 | COL3)
#define COL_MASK_P2         (COL0 | COL1)

static void delay_ms(unsigned int ms) {
    unsigned int i, j;
    for(i = 0; i < ms; i++)
        for(j = 0; j < 10000; j++);
}

static void set_column(unsigned int col)
{
    LPC_GPIO2->FIOSET = COL_MASK_P2;
    LPC_GPIO0->FIOSET = COL_MASK_P0;

    switch(col) {
        case 0: LPC_GPIO2->FIOCLR = COL0; break;
        case 1: LPC_GPIO2->FIOCLR = COL1; break;
        case 2: LPC_GPIO0->FIOCLR = COL2; break;
        case 3: LPC_GPIO0->FIOCLR = COL3; break;
    }
}

static unsigned int is_row0_pressed(void)
{
    return !(LPC_GPIO0->FIOPIN & ROW0);
}

void PWM1_IRQHandler(void)
{
    if (LPC_PWM1->IR & (1 << 0))
    {
        if(pwm_counter < duty_cycle)
            LPC_GPIO0->FIOSET = LED_MASK;
        else
            LPC_GPIO0->FIOCLR = LED_MASK;

        pwm_counter++;
        if(pwm_counter >= 3000)
            pwm_counter = 0;

        LPC_PWM1->IR = (1 << 0);
    }
}

int main(void)
{
    unsigned int col_idx;
    unsigned int read_key;
    unsigned int last_key = 0xFF;

    LPC_PINCON->PINSEL0 &= ~(0xFFFF << 8);
    LPC_PINCON->PINSEL1 &= ~(0xFFFF << 14);
    LPC_PINCON->PINSEL4 &= ~(0xF << 0);

    LPC_GPIO0->FIODIR |= LED_MASK;
    LPC_GPIO0->FIODIR |= COL_MASK_P0;
    LPC_GPIO2->FIODIR |= COL_MASK_P2;
    LPC_GPIO0->FIODIR &= ~ROW0;

    LPC_GPIO0->FIOCLR = LED_MASK;
    LPC_GPIO2->FIOSET = COL_MASK_P2;
    LPC_GPIO0->FIOSET = COL_MASK_P0;

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

    LPC_PWM1->MR0 = 3000;
    LPC_PWM1->MCR = (1 << 1) | (1 << 0);
    LPC_PWM1->LER = (1 << 0);

    NVIC_EnableIRQ(PWM1_IRQn);
    NVIC_SetPriority(PWM1_IRQn, 0);

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

    while(1)
    {
        read_key = 0xFF;

        for(col_idx = 0; col_idx < 4; col_idx++)
        {
            set_column(col_idx);
            delay_ms(5);

            if(is_row0_pressed()) {
                read_key = col_idx;

                while(is_row0_pressed()) {
                    delay_ms(10);
                }
                break;
            }
        }

        LPC_GPIO2->FIOSET = COL_MASK_P2;
        LPC_GPIO0->FIOSET = COL_MASK_P0;

        if(read_key != 0xFF && read_key != last_key) {
            last_key = read_key;

            switch(read_key) {
                case 0: duty_cycle = 300;   break;
                case 1: duty_cycle = 750;   break;
                case 2: duty_cycle = 1500;  break;
                case 3: duty_cycle = 2250;  break;
            }
        }

        delay_ms(50);
    }
}