qmk_firmware/keyboards/clueboard/66/rev3/rev3.c

#include "rev3.h"
#include "print.h"

void backlight_init_ports(void) {
    print("init_backlight_pin()\n");
    // Set our LED pins as output
    DDRD |= (1<<6); // Esc
    DDRB |= (1<<7); // Page Up
    DDRD |= (1<<4); // Arrows

    // Set our LED pins low
    PORTD &= ~(1<<6); // Esc
    PORTB &= ~(1<<7); // Page Up
    PORTD &= ~(1<<4); // Arrows
}

void backlight_set(uint8_t level) {
    if ( level == 0 ) {
        // Turn off light
        PORTD |= (1<<6); // Esc
        PORTB |= (1<<7); // Page Up
        PORTD |= (1<<4); // Arrows
    } else {
        // Turn on light
        PORTD &= ~(1<<6); // Esc
        PORTB &= ~(1<<7); // Page Up
        PORTD &= ~(1<<4); // Arrows
    }
}