private EchoStatus ProcessEcho(int echoLength)
{
if (port == null || messageProcessor == null)
{
throw new InvalidOperationException();
}
var data = ReadData(echoLength, true);
if (data.Length == 0)
{
logger.ErrorFormat("No data read from port");
return(EchoStatus.None);
}
// if the first byte is a NAK (15) then return a NAK and add whatever additional data was read to the buffer
if (data[0] == (byte)EchoStatus.NAK)
{
logger.DebugFormat("RX: {0}", Utilities.ByteArrayToString(data));
if (data.Length > 1)
{
int remainingCount = data.Length - 1;
var remainingData = new byte[remainingCount];
Array.Copy(data, 1, remainingData, 0, remainingCount);
lock (buffer)
buffer.AddRange(remainingData);
ProcessData(); //process the rest of the data stream
}
return(EchoStatus.NAK);
}
// scan until a MESSAGE START byte (02) is detected, which should be the first byte
int offset = 0;
while (offset < data.Length)
{
if (data[offset++] == Constants.MessageStartByte)
{
break;
}
}
// exit if no MESSAGE START byte detected
if (offset >= data.Length)
{
logger.DebugFormat("RX: {0} ERROR - Failed to find MESSAGE START byte (02)", Utilities.ByteArrayToString(data));
return(EchoStatus.Unknown);
}
logger.DebugFormat("RX: {0}", Utilities.ByteArrayToString(data));
// warn about any skipped bytes
if (offset > 1)
{
logger.WarnFormat("Skipping {0} bytes to '{1}', discarded '{2}'", offset - 1, Utilities.ByteArrayToString(data, offset - 1), Utilities.ByteArrayToString(data, 0, offset - 1));
}
// process the echo and decode the trailing status byte
int count;
if (messageProcessor.ProcessEcho(data, offset, out count))
{
int j = offset + count;
byte result = j < data.Length ? data[j] : Byte.MinValue;
j += 1;
if (data.Length > j) // if there's data beyond the echo then add it to the buffer
{
int remainingCount = data.Length - j;
var remainingData = new byte[remainingCount];
Array.Copy(data, j, remainingData, 0, remainingCount);
lock (buffer)
buffer.AddRange(remainingData);
ProcessData(); //process the rest of the data stream
}
if (result == (byte)EchoStatus.ACK)
{
messageProcessor.SetEchoStatus(EchoStatus.ACK);
logger.DebugFormat("PLM: {0} ACK", Utilities.ByteArrayToString(data, offset - 1, count + 2)); // +1 for MESSAGE START byte (02), +1 for ACK byte (06)
return(EchoStatus.ACK);
}
if (result == (byte)EchoStatus.NAK)
{
logger.DebugFormat("PLM: {0} NAK", Utilities.ByteArrayToString(data, offset - 1, count + 2)); // +1 for MESSAGE START byte (02), +1 for NAK byte (15)
messageProcessor.SetEchoStatus(EchoStatus.NAK);
return(EchoStatus.NAK);
}
logger.DebugFormat("PLM: {0} Unknown trailing byte", Utilities.ByteArrayToString(data, offset - 1, count + 2)); // +1 for MESSAGE START byte (02), +1 for unknown byte
messageProcessor.SetEchoStatus(EchoStatus.Unknown);
return(EchoStatus.Unknown);
}
logger.DebugFormat("PLM: {0} Echo mismatch", Utilities.ByteArrayToString(data, offset - 1));
return(EchoStatus.Unknown);
}
