/// <summary>
/// Sends a modbus telegram over the interface and waits for a response
/// </summary>
/// <param name="deviceAddress">Modbus device address.</param>
/// <param name="fc">Function code.</param>
/// <param name="timeout">Timeout in Milli seconds.</param>
/// <param name="telegramLength">Total length of the telegram in bytes</param>
/// <param name="desiredDataLength">Length of the desired telegram data (without fc, cs, ...) of the response in bytes. -1 for unknown.</param>
/// <param name="telegramContext">Interface specific context of the telegram</param>
/// <param name="dataPos">Index of the response data in the buffer.</param>
/// <returns></returns>
protected virtual short SendReceive(byte deviceAddress, ModbusFunctionCode fc, int timeout, short telegramLength, short desiredDataLength,
object telegramContext, ref short dataPos)
{
lock (_SyncObject)
{
try
{
_Interface.SendTelegram(_Buffer, telegramLength);
_Interface.PrepareRead();
if (deviceAddress == ModbusConst.BroadcastAddress)
{
return(0);
}
byte responseDeviceAddress;
byte responseFc = 0;
short dataLength = 0;
while (timeout > 0)
{
var ts = DateTime.Now.Ticks;
if (!_Interface.ReceiveTelegram(_Buffer, desiredDataLength, timeout, out telegramLength))
{
throw new ModbusException(ModbusErrorCode.Timeout);
}
timeout -= (int)((DateTime.Now.Ticks - ts) / 10000);
// if this is not the response we are waiting for wait again until time runs out
if (_Interface.ParseTelegram(_Buffer, telegramLength, true, ref telegramContext,
out responseDeviceAddress,
out responseFc,
out dataPos, out dataLength) &&
responseDeviceAddress == deviceAddress &&
(responseFc & 0x7f) == (byte)fc)
{
break;
}
if (timeout <= 0)
{
throw new ModbusException(ModbusErrorCode.Timeout);
}
}
if ((responseFc & 0x80) != 0)
{
// error response
throw new ModbusException((ModbusErrorCode)_Buffer[dataPos]);
}
return(dataLength);
}
finally
{
_Interface.PrepareWrite();
}
}
}
private short SendReceive(IModbusInterface masterInterface, byte[] buffer, byte deviceAddress, ModbusFunctionCode fc, int timeout, short telegramLength, short desiredDataLength,
object telegramContext, ref short dataPos)
{
lock (masterInterface)
{
masterInterface.SendTelegram(buffer, telegramLength);
if (deviceAddress == ModbusConst.BroadcastAddress)
{
return 0;
}
try
{
masterInterface.PrepareRead();
byte responseDeviceAddress;
byte responseFc = 0;
short dataLength = 0;
while (timeout > 0)
{
var ts = DateTime.Now.Ticks;
if (!masterInterface.ReceiveTelegram(buffer, desiredDataLength, timeout, out telegramLength))
{
throw new ModbusException(ModbusErrorCode.Timeout);
}
timeout -= (int) ((DateTime.Now.Ticks - ts)/10000);
// if this is not the response we are waiting for wait again until time runs out
if (masterInterface.ParseTelegram(buffer, telegramLength, true, ref telegramContext,
out responseDeviceAddress,
out responseFc,
out dataPos, out dataLength)
&& responseDeviceAddress == deviceAddress
&& (responseFc & 0x7f) == (byte) fc)
{
break;
}
if (timeout <= 0)
{
throw new ModbusException(ModbusErrorCode.Timeout);
}
}
if ((responseFc & 0x80) != 0)
{
// error response
throw new ModbusException((ModbusErrorCode) buffer[dataPos]);
}
return dataLength;
}
finally
{
masterInterface.PrepareWrite();
}
}
}
