modbus.h

/* 
 * Copyright 2016 Kim Taylor
 * Based on libmodbus by Stéphane Raimbault <stephane.raimbault@gmail.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/* Function codes */
#define _FC_READ_COILS                0x01
#define _FC_READ_DISCRETE_INPUTS      0x02
#define _FC_READ_HOLDING_REGISTERS    0x03
#define _FC_READ_INPUT_REGISTERS      0x04
#define _FC_WRITE_SINGLE_COIL         0x05
#define _FC_WRITE_SINGLE_REGISTER     0x06
#define _FC_READ_EXCEPTION_STATUS     0x07
#define _FC_WRITE_MULTIPLE_COILS      0x0F
#define _FC_WRITE_MULTIPLE_REGISTERS  0x10
#define _FC_REPORT_SLAVE_ID           0x11
#define _FC_MASK_WRITE_REGISTER       0x16
#define _FC_WRITE_AND_READ_REGISTERS  0x17

#define MODBUS_EXCEPTION 0x80
enum {
    MODBUS_EXCEPTION_ILLEGAL_FUNCTION = 0x01,
    MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS,
    MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE,
    MODBUS_EXCEPTION_SLAVE_OR_SERVER_FAILURE,
    MODBUS_EXCEPTION_ACKNOWLEDGE,
    MODBUS_EXCEPTION_SLAVE_OR_SERVER_BUSY,
    MODBUS_EXCEPTION_NEGATIVE_ACKNOWLEDGE,
    MODBUS_EXCEPTION_MEMORY_PARITY,
    MODBUS_EXCEPTION_NOT_DEFINED,
    MODBUS_EXCEPTION_GATEWAY_PATH,
    MODBUS_EXCEPTION_GATEWAY_TARGET,
    MODBUS_EXCEPTION_MAX,
};

/* Offsets from the user function perspective */
#define MODBUS_MSG_LEN_OFFSET	    0
#define MODBUS_MSG_ADDR_OFFSET	    0
#define MODBUS_MSG_NR_REGS_OFFSET   2

#define MODBUS_WRITE_RESP_SIZE	    4

/* Helper functions */
extern uint16_t mb_address;
extern uint8_t mb_nr_regs;
extern uint8_t mb_resp_bytes;
extern int8_t modbus_slave_id_response(uint8_t *msg);
extern void mb_data_init(uint8_t *msg, uint8_t fn);
extern void mb_data_resp(uint8_t *msg, uint16_t val);
extern uint16_t mb_data_next(uint8_t *msg);

/* Limits for user function */
#define MAX_NR_REGS(fn) (   fn == _FC_READ_HOLDING_REGISTERS ?		    \
				(MODBUS_MAX_PACKET_LENGTH - 5)/2 :	    \
			    fn == _FC_WRITE_MULTIPLE_REGISTERS ?	    \
				(MODBUS_MAX_PACKET_LENGTH - 9)/2 :	    \
			    0)
			    

#define MB_UINT16_T(ptr) ((uint16_t) *ptr << 8 | *(ptr + 1))

static uint16_t mb_buf_to_val(uint8_t *buf) {
    return (uint16_t) buf[0] << 8 | buf[1];
}

static uint8_t mb_val_to_buf(uint8_t *buf, uint16_t val) {
    buf[0] = val >> 8;
    buf[1] = val;
    return 2;
}

typedef void	(*modbus_write_t)	(const uint8_t *msg, uint8_t bytes);
typedef uint8_t (*modbus_read_t)	(void);
typedef uint8_t (*modbus_read_ready_t)	(void);
typedef int8_t	(*modbus_process_t)	(uint8_t function, uint8_t *msg);
typedef void	(*modbus_forward_t)	(const uint8_t *msg, uint8_t bytes);

#if MODBUS_USE_FUNCTION_POINTERS
extern void modbus_init(
	    uint8_t		slave_addr, 
	    modbus_write_t	modbus_write,
	    modbus_read_ready_t	modbus_read_ready,
	    modbus_read_t	modbus_read,
	    modbus_process_t	modbus_process,
	    modbus_forward_t	modbus_forward);
#else
extern void modbus_init(uint8_t slave_addr);
#endif

extern uint8_t modbus_poll(void);

#define MODBUS_ACTIVE_HIGH  1
#define MODBUS_ACTIVE_LOW   0
extern void modbus_tx_led(void (*led_enable)(uint8_t val), uint8_t val);
extern void modbus_rx_led(void (*led_enable)(uint8_t val), uint8_t val);