/// <summary>
/// Create a single packet MDC1200 data array.
/// </summary>
/// <param name="packet">MDC packet to create</param>
public void CreateSingle(MDCPacket packet)
{
Messages.Trace("Creating single-length MDC1200 packet " + packet.ToString());
// initialize MDC1200 header
GenerateHeader(ref dataArray, ref dataLoaded, NumberOfPreambles, true);
// create a temporary array DATA_SIZE - 12 (stripping the size used by
// the header)
byte[] dp = new byte[CODEWORD_LENGTH];
// fill the first bytes with the proper opcode and argument data
dp[0] = packet.Operation;
dp[1] = packet.Argument;
dp[2] = (byte)((packet.UnitID >> 8) & 0x00FF);
dp[3] = (byte)(packet.UnitID & 0x00FF);
// pack data
PackData(dp);
// block copy new data into MDC1200 data array
Buffer.BlockCopy(dp, 0, this.dataArray, dataLoaded, dp.Length);
this.dataLoaded += 14;
// dump output data for debug purposes
Messages.TraceHex("Raw Data Dump", dataArray);
}
/// <summary>
/// Internal function to process the bits of a MDC1200 data stream.
/// </summary>
/// <param name="idx">Decoder Index</param>
/// <returns>True, if CRC was matched and decoding succeeded, otherwise false</returns>
private bool ProcessBits(int idx)
{
int[] lbits = new int[MAX_MDC1200_BITS];
int lbc = 0;
byte[] data = new byte[14];
ushort ccrc, rcrc;
// do deep magic bit manipulation
for (int i = 0; i < 16; i++)
{
// loop through 8 bits
for (int j = 0; j < 7; j++)
{
int k = (j * 16) + i;
lbits[lbc] = this.bits[idx, k];
++lbc;
}
}
for (int i = 0; i < 14; i++)
{
data[i] = 0;
// loop through 8 bits (get each byte)
for (int j = 0; j < 8; j++)
{
int k = (i * 8) + j;
if (lbits[k] != 0)
{
data[i] |= (byte)(1 << j);
}
}
}
// compute CRC
ccrc = ComputeCRC(data, 4);
rcrc = (ushort)(data[5] << 8 | data[4]);
// dump output data for debug purposes
Messages.TraceHex("Decoded Data Dump CCRC " + ccrc.ToString("X4") + " RCRC " + rcrc.ToString("X4"), data);
// compare the computed CRC to the recieved CRC
if (ccrc == rcrc)
{
byte crc;
if (this.shstate[idx] == 2)
{
// copy second packet data
second.Operation = data[0];
second.Argument = data[1];
second.UnitID = (ushort)((data[2] << 8) | data[3]);
// reset the states for all decoders
for (int k = 0; k < MDC_ND; k++)
{
this.shstate[k] = 0;
}
this.frameCount = 2;
}
else
{
this.frameCount = 1;
// copy first packet data
first.Operation = data[0];
first.Argument = data[1];
first.UnitID = (ushort)((data[2] << 8) | data[3]);
crc = (byte)((data[4] << 8) | data[5]);
// reset the states for all decoders
for (int k = 0; k < MDC_ND; k++)
{
this.shstate[k] = 0;
}
// check if the operation code is for a "double" packet
switch (data[0])
{
case OpType.DOUBLE_PACKET_TYPE1:
case OpType.DOUBLE_PACKET_TYPE2:
{
// we have a double packet reset the frame count to 0
// and set the state to reflect a double packet
this.frameCount = 0;
this.shstate[idx] = 2;
this.shcount[idx] = 0;
ClearBits(idx);
}
break;
default:
break;
}
}
// if our frame count is non-zero execute the decoded callback
if (this.frameCount > 0)
{
Messages.Trace("Frame Count: " + frameCount);
Messages.Trace("MDC Frame 1 = " + ToString(first));
// if we have a frame count of > 1 then display second packet data
if (this.frameCount > 1)
{
Messages.Trace("MDC Frame 2 = " + ToString(second));
}
Messages.Trace("MDC1200 packet First (" + first.ToString() + "), Second (" + second.ToString() + ")");
// fire event
if (DecoderCallback != null)
{
DecoderCallback(this.frameCount, first, second);
}
// reset frame count
this.frameCount = 0;
}
return(true);
}
else
{
Messages.Trace("CRC Mismatch! Bad MDC Frame " + this.frameCount);
// since the CRC is bad reset the frame count
this.frameCount = 0;
this.shstate[idx] = -1;
}
return(false);
}