Modbus.h

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#ifndef __MODBUS_H__
#define __MODBUS_H__
 
 
#include "stdint.h"
#include "stdbool.h"
#include "stdlib.h"
#include "string.h"
 
#ifdef __cplusplus
extern "C" {
#endif
 
#define MODBUS_BROADCAST_ADDRESS 0
 
/* Modbus_Application_Protocol_V1_1b.pdf (chapter 6 section 1 page 12)
 * Quantity of Coils to read (2 bytes): 1 to 2000 (0x7D0)
 * (chapter 6 section 11 page 29)
 * Quantity of Coils to write (2 bytes): 1 to 1968 (0x7B0)
 */
#define MODBUS_MAX_READ_BITS  2000
#define MODBUS_MAX_WRITE_BITS 1968
 
/* Modbus_Application_Protocol_V1_1b.pdf (chapter 6 section 3 page 15)
 * Quantity of Registers to read (2 bytes): 1 to 125 (0x7D)
 * (chapter 6 section 12 page 31)
 * Quantity of Registers to write (2 bytes) 1 to 123 (0x7B)
 * (chapter 6 section 17 page 38)
 * Quantity of Registers to write in R/W registers (2 bytes) 1 to 121 (0x79)
 */
#define MODBUS_MAX_READ_REGISTERS     125
#define MODBUS_MAX_WRITE_REGISTERS    123
#define MODBUS_MAX_WR_WRITE_REGISTERS 121
#define MODBUS_MAX_WR_READ_REGISTERS  125
 
/* The size of the MODBUS PDU is limited by the size constraint inherited from
 * the first MODBUS implementation on Serial Line network (max. RS485 ADU = 256
 * bytes). Therefore, MODBUS PDU for serial line communication = 256 - Server
 * address (1 byte) - CRC (2 bytes) = 253 bytes.
 */
#define MODBUS_MAX_PDU_LENGTH 253
 
 
/* Modbus_Application_Protocol_V1_1b.pdf Chapter 4 Section 1 Page 5
 * RS232 / RS485 ADU = 253 bytes + slave (1 byte) + CRC (2 bytes) = 256 bytes
 */
#define MODBUS_RTU_MAX_ADU_LENGTH 256
 
 
bool Modbus_Payload_Check_CRC(uint8_t *payload,size_t payload_length);
 
 
 
bool Modbus_Payload_Append_CRC(uint8_t *payload,size_t payload_length);
 
 
typedef struct
{
 
 
    uint8_t slave_addr;
    void (*output)(uint8_t *data,size_t data_length);
 
    bool (*read_IX)(size_t addr);
 
    void (*write_OX)(size_t addr,uint16_t data);
    bool (*read_OX)(size_t addr);
 
    uint16_t (*read_hold_register)(size_t addr);
    void (*write_hold_register)(size_t addr,uint16_t data);
 
    uint16_t (*read_input_register)(size_t addr);
 
 
} modbus_slave_context_t;
 
 
 
bool Modbus_Slave_Parse_Input(modbus_slave_context_t *ctx,uint8_t *input_data,size_t input_data_length,uint8_t *buff,size_t buff_length);
 
 
typedef struct
{
    uint8_t slave_addr;
    void (*output)(uint8_t *data,size_t data_length);
 
 
    size_t (*request_reply)(uint8_t *data,size_t data_length);
 
} modbus_master_context_t;
 
 
 
bool Modbus_Master_Read_IX(modbus_master_context_t *ctx,uint16_t start_addr,bool *data,size_t number,uint8_t *buff,size_t buff_length);
 
bool Modbus_Master_Read_OX(modbus_master_context_t *ctx,uint16_t start_addr,bool *data,size_t number,uint8_t *buff,size_t buff_length);
 
bool Modbus_Master_Read_Hold_Register(modbus_master_context_t *ctx,uint16_t start_addr,uint16_t *data,size_t number,uint8_t *buff,size_t buff_length);
 
bool Modbus_Master_Read_Input_Register(modbus_master_context_t *ctx,uint16_t start_addr,uint16_t *data,size_t number,uint8_t *buff,size_t buff_length);
 
bool Modbus_Master_Write_OX(modbus_master_context_t *ctx,uint16_t start_addr,bool *data,size_t number,uint8_t *buff,size_t buff_length);
 
bool Modbus_Master_Write_Hold_Register(modbus_master_context_t *ctx,uint16_t start_addr,uint16_t *data,size_t number,uint8_t *buff,size_t buff_length);
 
#ifdef __cplusplus
}
#endif
 
 
#endif