qmk_firmware/keyboards/acr60/acr60.c

#include "acr60.h"
#include "led.h"

void matrix_init_kb(void) {
  // Keyboard start-up code goes here
  // Runs once when the firmware starts up
  matrix_init_user();
  led_init_ports();
};

void matrix_scan_kb(void) {
  // Looping keyboard code goes here
  // This runs every cycle (a lot)
  matrix_scan_user();
};

void led_init_ports(void) {
  // Set caps lock LED pin as output
  DDRB |= (1 << 2);
  // Default to off
  PORTB |= (1 << 2);
}

void led_set_kb(uint8_t usb_led) {
  // Code for caps lock LED as reported by the OS
  // Set this per keymap, instead of globally
  led_set_user(usb_led);
}