/// <summary>
/// Sends the given telegram.
/// If necessary additional information like a checksum can be inserted here.
/// </summary>
/// <param name="buffer">Buffer containing the data.</param>
/// <param name="telegramLength">Length of the telegram in bytes.</param>
public void SendTelegram(byte[] buffer, short telegramLength)
{
var crc = ModbusUtils.CalcCrc(buffer, telegramLength - 2);
buffer[telegramLength - 2] = (byte)(crc & 0x00ff);
buffer[telegramLength - 1] = (byte)((crc & 0xff00) >> 8);
// ticks and _NextSend are multiples of 100 ns
var dt = _nextSend - DateTime.Now.Ticks;
if (dt > 0)
{
Thread.Sleep(Math.Max(1, (int)dt / 10000));
}
// clear buffers
_serial.DiscardInBuffer();
_serial.DiscardOutBuffer();
// next send is 3.5 chars after the end of this telegram
_nextSend = DateTime.Now.Ticks + (telegramLength * 2 + 7) * _halfCharLength;
#if NETMF
try
{
_serial.Write(buffer, 0, telegramLength);
// make sure all bytes are sent out
_serial.Flush();
}
catch (ArgumentException)
{
// happens some times -> Close -> Open -> try again
try
{
_serial.Close();
}
catch
{
// ignored
}
_serial.Open();
_serial.Write(buffer, 0, telegramLength);
_serial.Flush();
}
#else
_serial.Write(buffer, 0, telegramLength);
#endif
}
/// <summary>
/// Parses a telegram received by ReceiveTelegram.
/// </summary>
/// <param name="buffer">Buffer containing the data.</param>
/// <param name="telegramLength">Total length of the telegram in bytes.</param>
/// <param name="isResponse">true if the telegram is a response telegram; false if the telegram is a request telegram.</param>
/// <param name="telegramContext">
/// If isResponse == true: pass the telegramContext returned by CreateTelegram from the request.
/// If isResponse == false: returns the telegramContext from the received request. It must pe passed to the CreateTelegram method for the response.
/// </param>
/// <param name="address">Returns the device address.</param>
/// <param name="fkt">Returns the function code.</param>
/// <param name="dataPos">Returns the offset in buffer of the function code specific data.</param>
/// <param name="dataLength">Returns the length of the function code specific data.</param>
/// <returns>Returns true if this is the matching response according to the telegramContext; else false. If isResponse == false this method should return always true.</returns>
public bool ParseTelegram(byte[] buffer, short telegramLength, bool isResponse, ref object telegramContext, out byte address, out byte fkt,
out short dataPos, out short dataLength)
{
if (telegramLength < 4)
{
throw new ModbusException(ModbusErrorCode.ResponseTooShort);
}
var crc = ModbusUtils.CalcCrc(buffer, telegramLength - 2);
if (buffer[telegramLength - 2] != (byte)(crc & 0x00ff) ||
buffer[telegramLength - 1] != (byte)((crc & 0xff00) >> 8))
{
throw new ModbusException(ModbusErrorCode.CrcError);
}
address = buffer[0];
fkt = buffer[1];
dataPos = 2;
dataLength = (short)(telegramLength - 4);
return(true);
}
/// <summary>
/// Sends the given telegram.
/// If necessary additional information like a checksum can be inserted here.
/// </summary>
/// <param name="buffer">Buffer containing the data.</param>
/// <param name="telegramLength">Length of the telegram in bytes.</param>
public void SendTelegram(byte[] buffer, short telegramLength)
{
var crc = ModbusUtils.CalcCrc(buffer, telegramLength - 2);
buffer[telegramLength - 2] = (byte)(crc & 0x00ff);
buffer[telegramLength - 1] = (byte)((crc & 0xff00) >> 8);
// ticks and _NextSend are multiples of 100 ns
var dt = this.nextSend - DateTime.Now.Ticks;
if (dt > 0)
{
Thread.Sleep(Math.Max(1, (int)dt / 10000));
}
// clear buffers
this.serial.ClearReadBuffer();
this.serial.ClearWriteBuffer();
// next send is 3.5 chars after the end of this telegram
this.nextSend = DateTime.Now.Ticks + (telegramLength * 2 + 7) * this.halfCharLength;
this.serial.Write(buffer, 0, telegramLength);
}
/// <summary>
/// Waits and receives a telegram.
/// </summary>
/// <param name="buffer">Buffer to write data into.</param>
/// <param name="desiredDataLength">Desired length of the function code specific data in bytes. -1 if length is unknown.</param>
/// <param name="timeout">Timeout in milliseconds to wait for the telegram.</param>
/// <param name="telegramLength">Returns the total length of the telegram in bytes.</param>
/// <returns>Returns true if the telegram was received successfully; false on timeout.</returns>
public bool ReceiveTelegram(byte[] buffer, short desiredDataLength, int timeout, out short telegramLength)
{
short desiredLength;
if (desiredDataLength >= 0)
{
desiredLength = (short)(desiredDataLength + 4);
if (desiredLength > buffer.Length)
{
throw new ArgumentException(string.Concat("buffer size (", buffer.Length, ") must be at least 4 byte larger than desiredDataLength (", desiredDataLength, ")"));
}
}
else
{
desiredLength = -1;
}
var n = 0;
var tOut = DateTime.Now.AddMilliseconds(timeout);
long nextRead = 0;
var errorChecked = false;
while (true)
{
//if ((desiredLength > 0 || n == 0) && DateTime.Now > tOut)
if (DateTime.Now > tOut)
{
break;
}
if (this.serial.BytesToRead > 0)
{
if (desiredLength > 0)
{
n += this.serial.Read(buffer, n, desiredLength - n);
}
else
{
n += this.serial.Read(buffer, n, buffer.Length - n);
}
// a delay of more than 1.5 chars means end of telegram /////, but since this is a extreme short time, we extend it by factor 2
nextRead = DateTime.Now.Ticks + 6 * this.halfCharLength;
}
if (!errorChecked && n >= 2)
{
errorChecked = true;
if ((buffer[1] & 0x80) != 0)
{
// modbus error, so desired length is 5
desiredLength = 5;
}
}
if (desiredLength > 0 && n == desiredLength)
{
telegramLength = (short)n;
return(true);
}
if (desiredLength <= 0 && n >= 2 && DateTime.Now.Ticks > nextRead && this.serial.BytesToRead == 0)
{
var crc = ModbusUtils.CalcCrc(buffer, n - 2);
if (buffer[n - 2] != (byte)(crc & 0x00ff) ||
buffer[n - 1] != (byte)((crc & 0xff00) >> 8))
{
// read a little bit longer
Thread.Sleep(1);
nextRead = DateTime.Now.Ticks + 6 * this.halfCharLength;
}
else
{
telegramLength = (short)n;
return(true);
}
}
}
telegramLength = 0;
return(false);
}
