#ifndef __MODBUS_H
#define __MODBUS_H

#include <stdint.h>

// function codes
#define MODBUS_FC_READ_HOLDING_REGISTERS 0x03
#define MODBUS_FC_WRITE_SINGLE_REGISTER 0x06
#define MODBUS_FC_WRITE_MULTIPLE_REGISTERS 0x10

// errors
#define MODBUS_ERROR_NONE 0x00
#define MODBUS_ERROR_FUNCTION 0x01
#define MODBUS_ERROR_ADDRESS 0x02
#define MODBUS_ERROR_VALUE 0x03

uint8_t modbus_process_message(uint8_t *buf, uint16_t len, uint8_t slave_addr,
                               uint16_t *holding_registers,
                               uint16_t num_registers);
uint16_t modbus_create_response(uint8_t *response, uint8_t slave_addr,
                                uint8_t function, uint16_t address,
                                uint16_t value);
uint16_t modbus_create_error_response(uint8_t *response, uint8_t slave_addr,
                                      uint8_t function, uint8_t error_code);

#endif  // __MODBUS_H