Modbus Function Codes for Holding/Input Registers

Functions
void	Modbus::get_FC1 ()
void	Modbus::get_FC3 ()
int8_t	Modbus::process_FC16 (uint16_t *regs, uint8_t u8size)
	This method processes function 16 This method writes a word array assigned by the master.
int8_t	Modbus::process_FC3 (uint16_t *regs, uint8_t u8size)
	This method processes functions 3 & 4 This method reads a word array and transfers it to the master.
int8_t	Modbus::process_FC6 (uint16_t *regs, uint8_t u8size)
	This method processes function 6 This method writes a value assigned by the master to a single word.

Detailed Description

Function Documentation

get_FC1()

void Modbus::get_FC1 ( )

private

This method processes functions 1 & 2 (for master) This method puts the slave answer into master data buffer

TODO: finish its implementation

Definition at line 1261 of file ModbusRtu.h.

{
    uint8_t u8byte, i;
    u8byte = 0;
 
    //  for (i=0; i< au8Buffer[ 2 ] /2; i++) {
    //    au16regs[ i ] = word(
    //    au8Buffer[ u8byte ],
    //    au8Buffer[ u8byte +1 ]);
    //    u8byte += 2;
    //  }
}

get_FC3()

void Modbus::get_FC3 ( )

private

This method processes functions 3 & 4 (for master) This method puts the slave answer into master data buffer

Definition at line 1280 of file ModbusRtu.h.

{
    uint8_t u8byte, i;
    u8byte = 3;
 
    for (i = 0; i < au8Buffer[2] / 2; i++)
    {
        au16regs[i] = word(
            au8Buffer[u8byte],
            au8Buffer[u8byte + 1]);
        u8byte += 2;
    }
}

process_FC16()

int8_t Modbus::process_FC16 ( uint16_t * regs, uint8_t u8size )

private

This method processes function 16 This method writes a word array assigned by the master.

Returns

u8BufferSize Response to master length

Definition at line 1502 of file ModbusRtu.h.

{
    uint8_t u8func = au8Buffer[FUNC]; // get the original FUNC code
    uint8_t u8StartAdd = au8Buffer[ADD_HI] << 8 | au8Buffer[ADD_LO];
    uint8_t u8regsno = au8Buffer[NB_HI] << 8 | au8Buffer[NB_LO];
    uint8_t u8CopyBufferSize;
    uint8_t i;
    uint16_t temp;
 
    // build header
    au8Buffer[NB_HI] = 0;
    au8Buffer[NB_LO] = u8regsno;
    u8BufferSize = RESPONSE_SIZE;
 
    // write registers
    for (i = 0; i < u8regsno; i++)
    {
        temp = word(
            au8Buffer[(BYTE_CNT + 1) + i * 2],
            au8Buffer[(BYTE_CNT + 2) + i * 2]);
 
        regs[u8StartAdd + i] = temp;
    }
    u8CopyBufferSize = u8BufferSize + 2;
    sendTxBuffer();
 
    return u8CopyBufferSize;
}

process_FC3()

int8_t Modbus::process_FC3 ( uint16_t * regs, uint8_t u8size )

private

This method processes functions 3 & 4 This method reads a word array and transfers it to the master.

Returns

u8BufferSize Response to master length

Definition at line 1357 of file ModbusRtu.h.

{
 
    uint8_t u8StartAdd = word(au8Buffer[ADD_HI], au8Buffer[ADD_LO]);
    uint8_t u8regsno = word(au8Buffer[NB_HI], au8Buffer[NB_LO]);
    uint8_t u8CopyBufferSize;
    uint8_t i;
 
    au8Buffer[2] = u8regsno * 2;
    u8BufferSize = 3;
 
    for (i = u8StartAdd; i < u8StartAdd + u8regsno; i++)
    {
        au8Buffer[u8BufferSize] = highByte(regs[i]);
        u8BufferSize++;
        au8Buffer[u8BufferSize] = lowByte(regs[i]);
        u8BufferSize++;
    }
    u8CopyBufferSize = u8BufferSize + 2;
    sendTxBuffer();
 
    return u8CopyBufferSize;
}

process_FC6()

int8_t Modbus::process_FC6 ( uint16_t * regs, uint8_t u8size )

private

This method processes function 6 This method writes a value assigned by the master to a single word.

Returns

u8BufferSize Response to master length

Definition at line 1421 of file ModbusRtu.h.

{
 
    uint8_t u8add = word(au8Buffer[ADD_HI], au8Buffer[ADD_LO]);
    uint8_t u8CopyBufferSize;
    uint16_t u16val = word(au8Buffer[NB_HI], au8Buffer[NB_LO]);
 
    regs[u8add] = u16val;
 
    // keep the same header
    u8BufferSize = RESPONSE_SIZE;
 
    u8CopyBufferSize = u8BufferSize + 2;
    sendTxBuffer();
 
    return u8CopyBufferSize;
}