readHoldingRegister()

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

#include <Modbus86.h>

ModbusSlave bus;

ModbusSlaveNode node;

uint32_t command = 0;

uint32_t lasttime = 0;

uint8_t read_holding_registers( uint8_t function,

                                 uint16_t address,

                                 uint16_t length)

{

    for (int i = address; i < address + length; i++) {

        if (i == 16)

            node.writeHoldingRegister(i, command & 0xFFFF);

        else if (i == 17)

    }

    return MODBUS_SUCCESS;

}

uint8_t write_multiple_registers(   uint8_t function,

                                     uint16_t address,

                                     uint16_t length)

{

    int i;

    for (i = address; i < address + length; i++) {

        if (i == 16)

            command = (command & 0xFFFF0000) | node.readHoldingRegister(i);

        else if (i == 17)

            command =

                (command & 0x0000FFFF) | (node.readHoldingRegister(i) << 16);

    }

    return MODBUS_SUCCESS;

}

void setup()

{   

    Serial485.begin(115200);

    /* Modbus RTU Mode via RS485. */

    bus.begin(MODBUS_RTU, Serial485);

    /* Slave node with ID 11. */

    node.attach(11, bus);

    /* Set the callback function of Read Holding Registers (0x03). */

    node.cbFunc[MODBUS_CB_READ_HOLDING_REGISTERS]

                            = read_holding_registers;

    /* Set the callback function of Write Multiple Registers (0x10). */

    node.cbFunc[MODBUS_CB_WRITE_MULTIPLE_REGISTERS]

                            = write_multiple_registers;

}

void loop()

{

    uint32_t now;

    node.poll();

    now = millis();

    if (now - lasttime > 500) {

        lasttime = now;

        Serial.print("commnad = ");

        Serial.println(command);

    }

}