写一段modbus/modbus.h的头文件

以下是一个简单的 modbus/modbus.h 头文件示例：

#ifndef __MODBUS_H__
#define __MODBUS_H__

#include <stdint.h>
#include <stdbool.h>

/* Modbus function codes */
#define MODBUS_FC_READ_COILS         0x01
#define MODBUS_FC_READ_DISCRETE_INPUTS 0x02
#define MODBUS_FC_READ_HOLDING_REGISTERS 0x03
#define MODBUS_FC_READ_INPUT_REGISTERS 0x04
#define MODBUS_FC_WRITE_SINGLE_COIL  0x05
#define MODBUS_FC_WRITE_SINGLE_REGISTER 0x06
#define MODBUS_FC_WRITE_MULTIPLE_COILS 0x0F
#define MODBUS_FC_WRITE_MULTIPLE_REGISTERS 0x10

/* Modbus error codes */
#define MODBUS_EXCEPTION_ILLEGAL_FUNCTION 0x01
#define MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS 0x02
#define MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE 0x03
#define MODBUS_EXCEPTION_SLAVE_DEVICE_FAILURE 0x04
#define MODBUS_EXCEPTION_ACKNOWLEDGE 0x05
#define MODBUS_EXCEPTION_SLAVE_DEVICE_BUSY 0x06
#define MODBUS_EXCEPTION_MEMORY_PARITY_ERROR 0x08
#define MODBUS_EXCEPTION_GATEWAY_PATH_UNAVAILABLE 0x0A
#define MODBUS_EXCEPTION_GATEWAY_TARGET_DEVICE_FAILED_TO_RESPOND 0x0B

/* Modbus data types */
typedef uint8_t modbus_byte_t;
typedef uint16_t modbus_word_t;

/* Modbus register struct */
typedef struct {
    modbus_word_t address;
    modbus_word_t value;
} modbus_register_t;

/* Modbus context */
typedef struct {
    int socket;
    uint8_t *request;
    uint8_t *response;
    int request_length;
    int response_length;
    bool debug;
} modbus_t;

/* Modbus function prototypes */
int modbus_read_coils(modbus_t *ctx, int address, int num_coils, uint8_t *coil_status);
int modbus_read_discrete_inputs(modbus_t *ctx, int address, int num_inputs, uint8_t *input_status);
int modbus_read_holding_registers(modbus_t *ctx, int address, int num_registers, modbus_register_t *registers);
int modbus_read_input_registers(modbus_t *ctx, int address, int num_registers, modbus_register_t *registers);
int modbus_write_single_coil(modbus_t *ctx, int address, int coil_status);
int modbus_write_single_register(modbus_t *ctx, int address, int register_value);
int modbus_write_multiple_coils(modbus_t *ctx, int address, int num_coils, uint8_t *coil_status);
int modbus_write_multiple_registers(modbus_t *ctx, int address, int num_registers, modbus_register_t *registers);

#endif /* __MODBUS_H__ */

该头文件定义了 Modbus 协议的相关常量、数据类型和函数声明。其中包括了 Modbus 的功能码、异常码、数据类型、寄存器结构体和 Modbus 上下文等。函数声明包括了常用的读写操作函数，如读线圈、读寄存器、写单个线圈等。