#ifndef _MODBUS_H
#define _MODBUS_H

#include <string.h>
#include <inttypes.h>

/* Modbus function codes */
#define read_holding_regs  0x03
#define read_input_regs    0x04
#define write_single_reg   0x06

/* Helpful macros */
#define lowByte(w) ((uint8_t) ((w) & 0xff))
#define highByte(w) ((uint8_t) ((w) >> 8))
#define word(h, l) ((h << 8) | l)

/* Maximum response buffer size for Modbus nodes */
#define MAX_BUFSIZE    64

typedef struct {
    uint8_t        slave_id;
    uint16_t       response_buffer[MAX_BUFSIZE];
    uint8_t        rbuf_len;
    uint8_t        modbus_timeout;
    void*          modbus_uart;    
} modbus_slave_device;

typedef enum {
    MB_OK             =  0x0,
    MB_UART_ERR_1     =  0x1,
    MB_UART_ERR_2     =  0x2,
    MB_UART_ERR_3     =  0x3,
    MB_SLAVE_ID_ERR   =  0x4,
    MB_FUNC_ERR       =  0x5,
    MB_CRC_ERR        =  0x6
} MB_StatusTypeDef;

/* Platform-agnostic UART function pointers */
extern MB_StatusTypeDef (*MB_UART_Tx)(void*, uint16_t*, uint8_t*, uint8_t*);
extern MB_StatusTypeDef (*MB_UART_Rx)(void*, uint16_t*, uint8_t*, uint8_t*);


MB_StatusTypeDef modbus_transaction(uint8_t func, modbus_slave_device *device,
				     uint16_t rw_addr, int read_num,
				     uint16_t write_value);

MB_StatusTypeDef ReadHoldingRegisters(modbus_slave_device *device,
				      uint16_t reg_addr,
				      int read_num);

MB_StatusTypeDef ReadInputRegisters(modbus_slave_device *device,
				    uint16_t reg_addr,
				    int read_num);

MB_StatusTypeDef WriteSingleRegister(modbus_slave_device *device,
				     uint16_t reg_addr,
				     uint16_t write_val);

void ClearResponseBuffer(modbus_slave_device *device);

#endif