#include "LPC17xx.h"

// PWM variables
volatile unsigned long int duty_cycle = 10;  // Start at 10%
volatile unsigned long int pwm_counter = 0;

// Pin definitions
#define LED_SHIFT           4   // CNA: P0.4-P0.11
#define LED_MASK            (0xFF << LED_SHIFT)

// Keypad on CND - ROW-0
#define COL0                (1<<0)   // P2.0
#define COL1                (1<<1)   // P2.1
#define COL2                (1<<23)  // P0.23
#define COL3                (1<<24)  // P0.24
#define ROW0                (1<<25)  // P0.25

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

#define PWM_PERIOD          100      // 100 steps for percentage

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);
}

// HIGH-SPEED PWM Interrupt Handler
void PWM1_IRQHandler(void)
{
    if (LPC_PWM1->IR & (1 << 0))
    {
        // Fast software PWM for all 8 LEDs
        if(pwm_counter < duty_cycle)
            LPC_GPIO0->FIOSET = LED_MASK;  // All LEDs ON
        else
            LPC_GPIO0->FIOCLR = LED_MASK;  // All LEDs OFF

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

        LPC_PWM1->IR = (1 << 0);  // Clear interrupt flag
    }
}

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

    // === PIN CONFIGURATION ===
    LPC_PINCON->PINSEL0 &= ~(0xFFFF << 8);   // P0.4-P0.11 as GPIO
    LPC_PINCON->PINSEL1 &= ~(0xFFFF << 14);  // P0.23-P0.28 as GPIO
    LPC_PINCON->PINSEL4 &= ~(0xF << 0);      // P2.0-P2.1 as GPIO

    // === GPIO SETUP ===
    LPC_GPIO0->FIODIR |= LED_MASK;       // LEDs output
    LPC_GPIO0->FIODIR |= COL_MASK_P0;    // Columns output
    LPC_GPIO2->FIODIR |= COL_MASK_P2;    // Columns output
    LPC_GPIO0->FIODIR &= ~ROW0;          // Row input

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

    // === HIGH-SPEED PWM CONFIGURATION ===
    LPC_SC->PCONP |= (1 << 6);           // Power on PWM1

    LPC_PWM1->TCR = (1 << 1);            // Reset
    LPC_PWM1->CTCR = 0;                  // Timer mode
    LPC_PWM1->PR = 9;                    // Prescaler = 10
                                         // 100MHz / 10 = 10MHz timer clock

    LPC_PWM1->MR0 = 100;                 // Match every 100 ticks
                                         // Interrupt rate = 10MHz/100 = 100kHz
                                         // PWM frequency = 100kHz/100 = 1kHz
                                         // NO VISIBLE FLICKER!

    LPC_PWM1->MCR = (1 << 1) | (1 << 0); // Reset on MR0 + interrupt
    LPC_PWM1->LER = (1 << 0);            // Latch MR0

    NVIC_EnableIRQ(PWM1_IRQn);           // Enable interrupt
    NVIC_SetPriority(PWM1_IRQn, 0);      // Highest priority

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

    // === MAIN LOOP ===
    while(1)
    {
        read_key = 0xFF;

        // Scan ROW-0 only
        for(col_idx = 0; col_idx < 4; col_idx++)
        {
            set_column(col_idx);
            delay_ms(5);  // Short delay for stable reading

            if(is_row0_pressed()) {
                read_key = col_idx;  // Key 0, 1, 2, or 3

                // Wait for key release
                while(is_row0_pressed()) {
                    delay_ms(10);
                }
                break;
            }
        }

        // Restore columns
        LPC_GPIO2->FIOSET = COL_MASK_P2;
        LPC_GPIO0->FIOSET = COL_MASK_P0;

        // Update brightness immediately on key press
        if(read_key != 0xFF && read_key != last_key) {
            last_key = read_key;

            switch(read_key) {
                case 0: duty_cycle = 10;  break;  // 10%
                case 1: duty_cycle = 25;  break;  // 25%
                case 2: duty_cycle = 50;  break;  // 50%
                case 3: duty_cycle = 75;  break;  // 75%
            }
        }

        delay_ms(50);  // Main loop delay
    }
}