Functions
boolean	Modbus::getTimeOutState ()
	get communication watch-dog timer state

int8_t	Modbus::poll ()
	cyclic poll for master

int8_t	Modbus::poll (uint16_t *regs, uint8_t u8size)
	cyclic poll for slave

int8_t	Modbus::query (modbus_t telegram)
	only for master

Detailed Description

Function Documentation

◆ getTimeOutState()

boolean Modbus::getTimeOutState ( )

get communication watch-dog timer state

Return communication Watchdog state. It could be useful to reset outputs if the watchdog is fired.

Returns: TRUE if millis() > u32timeOut

Definition at line 506 of file ModbusRtu.h.

{
    return (millis() > u32timeOut);
}

◆ poll() [1/2]

int8_t Modbus::poll ( )

cyclic poll for master

*** Only for Modbus Master *** This method checks if there is any incoming answer if pending. If there is no answer, it would change Master state to COM_IDLE. This method must be called only at loop section. Avoid any delay() function.

Any incoming data would be redirected to au16regs pointer, as defined in its modbus_t query telegram.

@params nothing

Returns: errors counter

Definition at line 691 of file ModbusRtu.h.

{
    // check if there is any incoming frame
    uint8_t u8current;
    if (u8serno < 4)
    {
        u8current = port->available();
    }
    else
    {
        u8current = softPort->available();
    }
 
    if (millis() > u32timeOut)
    {
        u8state = COM_IDLE;
        u8lastError = NO_REPLY;
        u16errCnt++;
        return 0;
    }
 
    if (u8current == 0)
    {
        return 0;
    }
 
    // check T35 after frame end or still no frame end
    if (u8current != u8lastRec)
    {
        u8lastRec = u8current;
        u32time = millis() + T35;
        return 0;
    }
    if (millis() < u32time)
    {
        return 0;
    };
 
    // transfer Serial buffer frame to auBuffer
    u8lastRec = 0;
    int8_t i8state = getRxBuffer();
    if (i8state < 7)
    {
        u8state = COM_IDLE;
        u16errCnt++;
        Log.verboseln("Add error : %d - RX-Buffer < 7", i8state);
        printHex(rxBuffer, u8BufferSize);
        return i8state;
    }
 
    // validate message: id, CRC, FCT, exception
    uint8_t u8exception = validateAnswer();
    if (u8exception != 0)
    {
        Log.verboseln("ModbusRTU::poll : exception : %d", u8exception);
        u8state = COM_IDLE;
        return u8exception;
    }
 
    // process answer
    switch (au8Buffer[FUNC])
    {
    case MB_FC_READ_COILS:
    case MB_FC_READ_DISCRETE_INPUT:
        // call get_FC1 to transfer the incoming message to au16regs buffer
        get_FC1();
        break;
    case MB_FC_READ_INPUT_REGISTER:
    case MB_FC_READ_REGISTERS:
        // call get_FC3 to transfer the incoming message to au16regs buffer
        get_FC3();
        break;
    case MB_FC_WRITE_COIL:
    case MB_FC_WRITE_REGISTER:
    case MB_FC_WRITE_MULTIPLE_COILS:
    case MB_FC_WRITE_MULTIPLE_REGISTERS:
        // nothing to do
        break;
    default:
        break;
    }
    u8state = COM_IDLE;
    currentQuery->flags = QUERY_STATE::RESPONDED;
    return u8BufferSize;
}

◆ poll() [2/2]

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

cyclic poll for slave

*** Only for Modbus Slave *** This method checks if there is any incoming query Afterwards, it would shoot a validation routine plus a register query Avoid any delay() function !!!! After a successful frame between the Master and the Slave, the time-out timer is reset.

Parameters

*regs	register table for communication exchange
u8size	size of the register table

Returns: 0 if no query, 1..4 if communication error, >4 if correct query processed

Definition at line 790 of file ModbusRtu.h.

{
 
    au16regs = regs;
    u8regsize = u8size;
    uint8_t u8current;
 
    // check if there is any incoming frame
    if (u8serno < 4)
        u8current = port->available();
    else
        u8current = softPort->available();
 
    if (u8current == 0)
        return 0;
 
    // check T35 after frame end or still no frame end
    if (u8current != u8lastRec)
    {
        u8lastRec = u8current;
        u32time = millis() + T35;
        return 0;
    }
    if (millis() < u32time)
        return 0;
 
    u8lastRec = 0;
    int8_t i8state = getRxBuffer();
    u8lastError = i8state;
    if (i8state < 7)
        return i8state;
 
    // check slave id
    if (au8Buffer[ID] != u8id)
    {
        return 0;
    }
 
    // validate message: CRC, FCT, address and size
    uint8_t u8exception = validateRequest();
    if (u8exception > 0)
    {
        Serial.println("exception : 1");
        if (u8exception != NO_REPLY)
        {
            buildException(u8exception);
            sendTxBuffer();
        }
        u8lastError = u8exception;
        return u8exception;
    }
 
    u32timeOut = millis() + long(u16timeOut);
    u8lastError = 0;
 
    Log.verboseln("mb : process message : %d", FUNC);
 
    // process message
    switch (au8Buffer[FUNC])
    {
    case MB_FC_READ_COILS:
    case MB_FC_READ_DISCRETE_INPUT:
        return process_FC1(regs, u8size);
        break;
    case MB_FC_READ_INPUT_REGISTER:
    case MB_FC_READ_REGISTERS:
        return process_FC3(regs, u8size);
        break;
    case MB_FC_WRITE_COIL:
        return process_FC5(regs, u8size);
        break;
    case MB_FC_WRITE_REGISTER:
        return process_FC6(regs, u8size);
        break;
    case MB_FC_WRITE_MULTIPLE_COILS:
        return process_FC15(regs, u8size);
        break;
    case MB_FC_WRITE_MULTIPLE_REGISTERS:
        return process_FC16(regs, u8size);
        break;
    default:
        break;
    }
    currentQuery->flags = RESPONDED;
    return i8state;
}

◆ query()

int8_t Modbus::query ( modbus_t telegram )

only for master

*** Only Modbus Master *** Generate a query to an slave with a modbus_t telegram structure The Master must be in COM_IDLE mode. After it, its state would be COM_WAITING. This method has to be called only in loop() section.

See also: modbus_t