qmk-firmware/quantum/split_common/split_util.h

#ifndef SPLIT_KEYBOARD_UTIL_H
#define SPLIT_KEYBOARD_UTIL_H

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include "eeconfig.h"

// backlight level store index in serial_master_buffer[] for slave to read
#define SERIAL_BACKLIT_START   0x00

#define SLAVE_I2C_ADDRESS           0x32

extern volatile bool isLeftHand;

// slave version of matix scan, defined in matrix.c
void matrix_slave_scan(void);

void split_keyboard_setup(void);
bool has_usb(void);
void keyboard_slave_loop(void);

void matrix_master_OLED_init (void);

#endif