/// <summary>
/// Initializes the request ADU and calculates the response length.
/// </summary>
public virtual void InitReqADU(byte devAddr, TransMode transMode)
{
if (ReqPDU == null)
{
return;
}
int pduLen = ReqPDU.Length;
switch (transMode)
{
case TransMode.RTU:
ReqADU = new byte[pduLen + 3];
ReqADU[0] = devAddr;
Buffer.BlockCopy(ReqPDU, 0, ReqADU, 1, ReqPDU.Length);
ushort crc = ModbusUtils.CRC16(ReqADU, 0, pduLen + 1);
ReqADU[pduLen + 1] = (byte)(crc % 256);
ReqADU[pduLen + 2] = (byte)(crc / 256);
RespAduLen = RespPduLen + 3;
break;
case TransMode.ASCII:
byte[] aduBuf = new byte[pduLen + 2];
aduBuf[0] = devAddr;
Buffer.BlockCopy(ReqPDU, 0, aduBuf, 1, ReqPDU.Length);
aduBuf[pduLen + 1] = ModbusUtils.LRC(aduBuf, 0, pduLen + 1);
StringBuilder sbADU = new StringBuilder();
foreach (byte b in aduBuf)
{
sbADU.Append(b.ToString("X2"));
}
ReqADU = Encoding.ASCII.GetBytes(sbADU.ToString());
ReqStr = ModbusUtils.Colon + sbADU;
RespAduLen = RespPduLen + 2;
break;
default: // TransModes.TCP
ReqADU = new byte[pduLen + 7];
ReqADU[0] = 0;
ReqADU[1] = 0;
ReqADU[2] = 0;
ReqADU[3] = 0;
ReqADU[4] = (byte)((pduLen + 1) / 256);
ReqADU[5] = (byte)((pduLen + 1) % 256);
ReqADU[6] = devAddr;
Buffer.BlockCopy(ReqPDU, 0, ReqADU, 7, ReqPDU.Length);
RespAduLen = RespPduLen + 7;
break;
}
}
/// <summary>
/// Performs a request in the PDU mode.
/// </summary>
protected bool RtuRequest(DataUnit dataUnit)
{
bool result = false;
// send request
log.WriteLine(dataUnit.ReqDescr);
Connection.Write(dataUnit.ReqADU, 0, dataUnit.ReqADU.Length, ProtocolFormat.Hex, out string logText);
log.WriteLine(logText);
// receive response
// partial read to calculate PDU length
const int FirstCount = 2;
int readCnt = Connection.Read(InBuf, 0, FirstCount, Timeout, ProtocolFormat.Hex, out logText);
log.WriteLine(logText);
if (readCnt != FirstCount)
{
log.WriteLine(ModbusPhrases.CommErrorWithExclamation);
}
else if (InBuf[0] != dataUnit.ReqADU[0]) // validate device address
{
log.WriteLine(ModbusPhrases.IncorrectDevAddr);
}
else if (!(InBuf[1] == dataUnit.FuncCode || InBuf[1] == dataUnit.ExcFuncCode)) // validate function code
{
log.WriteLine(ModbusPhrases.IncorrectPduFuncCode);
}
else
{
int pduLen;
int count;
if (InBuf[1] == dataUnit.FuncCode)
{
pduLen = dataUnit.RespPduLen;
count = dataUnit.RespAduLen - FirstCount;
}
else // exception received
{
pduLen = 2;
count = 3;
}
// read rest of response
readCnt = Connection.Read(InBuf, FirstCount, count, Timeout, ProtocolFormat.Hex, out logText);
log.WriteLine(logText);
if (readCnt != count)
{
log.WriteLine(ModbusPhrases.CommErrorWithExclamation);
}
else if (InBuf[pduLen + 1] + InBuf[pduLen + 2] * 256 != ModbusUtils.CRC16(InBuf, 0, pduLen + 1))
{
log.WriteLine(ModbusPhrases.CrcError);
}
else if (dataUnit.DecodeRespPDU(InBuf, 1, pduLen, out string errMsg))
{
log.WriteLine(ModbusPhrases.OK);
result = true;
}
else
{
log.WriteLine(errMsg + "!");
}
}
return(result);
}