// returns the eqiv. array of bytes (with CRC checksum added) of a frame structure
public byte[] frame2Bytes(EZFrame frame)
{
int framelen = 5 + frame.PayloadLength + 4; // 5 header bytes plus payload, plus starter, terminator and CRC checksum
byte[] rawframe = new byte[framelen];
rawframe[0] = framestarter;
rawframe[1] = frame.SenderID;
rawframe[2] = frame.ReceiverID;
rawframe[3] = frame.Ftype;
rawframe[4] = (byte)(frame.PayloadLength & 0x0FF);
rawframe[5] = (byte)((frame.PayloadLength >> 8) & 0x0FF);
int i;
for (i = 0; i < frame.PayloadLength; i++)
{
rawframe[6 + i] = frame.Payload[i];
}
rawframe[framelen - 3] = frameterminator;
// now adding CRC
ushort crc = calculateCRC(rawframe, framelen - 2);
rawframe[framelen - 2] = (byte)(crc & 0x0FF);
rawframe[framelen - 1] = (byte)((crc >> 8) & 0x0FF);
return(rawframe);
}
// handle next frame
public void receivedNewFrame(EZFrame frame)
{
// sending acknowledgement
NetDevice.sendAcknowledge(PacketSenderID);
// copying payload bytes into the packet
int i;
int startindex = EZRoboNetDevice.MAX_FRAME_PAYLOAD_LENGTH * FramesReceived;
for (i = 0; i < frame.PayloadLength; i++)
{
CurrentPacket[startindex + i] = frame.Payload[i];
}
// frame payload copied
// increasing number of received frames
FramesReceived++;
// now changing state
if (FramesReceived == TotalFrames)
{
state = EZRoboNetDevice.stPacketReady;
}
else
{
state = EZRoboNetDevice.stReceiving;
// marking time for next frame arrival possible timeout
FrameReceptionStartTime = DateTime.Now;
}
}
// handling internal state according to input and triggering appropriate actions
public void transitionAction(EZFrame frame)
{
switch (state)
{
case EZRoboNetDevice.stReceiving: // in the process of receiving frames
switch (frame.Ftype)
{
case EZRoboNetDevice.t_Ping: // just reply and go back to wait for the next frame in the sequence
NetDevice.sendAcknowledge(frame.SenderID);
state = EZRoboNetDevice.stReceiving;
break;
case EZRoboNetDevice.t_Data: // Data frame arrived. See if we can fill the packet some more
if (PacketSenderID == frame.SenderID) // received a frame from the original sender
{
receivedNewFrame(frame);
}
else
{ // packet does not originate fron the current sender
// disposing inetercepted frame
state = EZRoboNetDevice.stReceiving; // still waiting for a new frame
}
break;
case EZRoboNetDevice.t_Acknowledge: // acknowledgment packet arrived
// do nothing. dispose the frame
break;
}
break;
case EZRoboNetDevice.stPacketReady: // a packet is ready to be handled
switch (frame.Ftype)
{
case EZRoboNetDevice.t_Ping: // ping frame
NetDevice.sendAcknowledge(frame.SenderID);
state = EZRoboNetDevice.stPacketReady;
break;
case EZRoboNetDevice.t_Acknowledge: // acknowledge frame
// ignore
state = EZRoboNetDevice.stPacketReady;
break;
case EZRoboNetDevice.t_Data: // a data frame
// ignore until packeready state has been served
state = EZRoboNetDevice.stPacketReady;
break;
}
break;
} // end big state switch
}
// create an acknowledgement frame
public EZFrame makeAcknowledge(byte receiver_id)
{
EZFrame frame = new EZFrame();
frame.SenderID = NodeID;
frame.ReceiverID = receiver_id;
frame.Ftype = t_Acknowledge;
frame.PayloadLength = 2;
frame.Payload = new byte[frame.PayloadLength];
frame.Payload[0] = 0;
frame.Payload[1] = 0;
return(frame);
}
// **************** handling the Incomplete Packets Queue **********************
// insert new packet reception FSM
public void InsertNewIncompletePacket(EZFrame frame)
{
int i;
// shifting the queue to the right
for (i = IncompletePacketsNum; i > 0; i--)
{
IncompletePackets[i] = IncompletePackets[i - 1];
}
// increasing number of Packets
IncompletePacketsNum++;
// adding new packet reception FSM
IncompletePackets[0] = new EZStationPacketFSM(this, frame);
}
// send acknowledgment
public void sendAcknowledge(byte receiver_id)
{
EZFrame ackframe = makeAcknowledge(receiver_id);
// converting struct to bytes
byte[] rawackframe = frame2Bytes(ackframe);
// retrieving length
ushort framelength = getRawFrameLength(rawackframe);
// sending bytes
CommPort.Write(rawackframe, 0, framelength);
// done
}
public EZStationPacketFSM(EZRoboNetDevice device, EZFrame frame)
{
// registering the Net Device
NetDevice = device;
// capturing time of first reception
ReceptionStartTime = DateTime.Now;
// acknowledging
NetDevice.sendAcknowledge(PacketSenderID);
// retrieving sender id
PacketSenderID = frame.SenderID;
// calculating total packet length
ushort packetlength = (ushort)(frame.Payload[3] + 256 * frame.Payload[4] + 5);
CurrentPacketLength = packetlength;
// calculating total number of frames required for full packet transmission
TotalFrames = packetlength / EZRoboNetDevice.MAX_FRAME_PAYLOAD_LENGTH + 1;
// allocating memory space for the packet being received
CurrentPacket = new byte[packetlength];
// now filling initial space in CurrentPacket
int i;
for (i = 0; i < frame.PayloadLength; i++)
{
CurrentPacket[i] = frame.Payload[i];
}
// done copying
// setting number of frames received to 1
FramesReceived = 1;
// sending an acknowledgement frame
NetDevice.sendAcknowledge(frame.SenderID);
if (FramesReceived < TotalFrames)
{ // need to receive more
state = EZRoboNetDevice.stReceiving;
// marrking time of acknowledgement
FrameReceptionStartTime = DateTime.Now;
}
else
{
state = EZRoboNetDevice.stPacketReady;
FramesReceived = 0;
TotalFrames = 0;
}
}
// send the next frame of the current packet
public void sendNextFrame()
{
// creating the first frame
EZFrame frame = new EZFrame();
frame.SenderID = NodeID;
frame.ReceiverID = PacketReceiverID;
frame.Ftype = t_Data;
ushort payloadlen, index;
index = (ushort)(FramesSent * MAX_FRAME_PAYLOAD_LENGTH);
if (FramesSent == TotalFrames - 1)
{
payloadlen = (ushort)(CurrentPacketLength % MAX_FRAME_PAYLOAD_LENGTH);
}
else
{
payloadlen = MAX_FRAME_PAYLOAD_LENGTH;
}
int i;
frame.PayloadLength = payloadlen;
frame.Payload = new byte[payloadlen];
for (i = 0; i < payloadlen; i++)
{
frame.Payload[i] = CurrentPacket[i + index];
}
// frame created
byte[] rawframe = frame2Bytes(frame);
int rawframelen = getRawFrameLength(rawframe);
// stream the packet through the serial port with a delay per character
CommPort.Write(rawframe, 0, rawframelen);
// god forbid, packet was sent. Changing state now
state = stWaitingAcknowledge;
// marking frame transmission time for possible acknowledge timeout
FrameTransmissionStartTime = DateTime.Now;
}
// Convert bytes to a Frame structure
public EZFrame bytes2Frame(byte[] rawframe)
{
EZFrame frame = new EZFrame();
ushort payloadlen = (ushort)(rawframe[4] + 256 * rawframe[5]);
frame.SenderID = rawframe[1];
frame.ReceiverID = rawframe[2];
frame.Ftype = rawframe[3];
frame.PayloadLength = payloadlen;
frame.Payload = new byte[payloadlen];
int i;
for (i = 0; i < payloadlen; i++)
{
frame.Payload[i] = rawframe[6 + i];
}
return(frame);
}
// processData. processData assembles the frames and calls to transitionAction
public void processData(SerialBuffer sBuffer)
{
int i;
int numBytesToRead = sBuffer.bytesAvailable(); // let's see what we 've got...
do
{
if (remainingBytes == 0) // previous frame was fully read
{
if (numBytesToRead >= 6) // nead at least 6 bytes to read frame header
// get the first 6 bytes (starter(1)+sender-receiverid(2)+frame type(1)+payload length (2))
// reading first 6 bytes into FrameHead
{
sBuffer.readBytes(FrameHead, 6);
// now cheking for framestarter character mismatch
if (FrameHead[0] != framestarter)
{
flushSerialBuffer(sBuffer);
}
else // reamaining bytes should be the payload length plus the terminator and two CRC bytes
{
remainingBytes = FrameHead[4] + FrameHead[5] * 256 + 3;
}
}
}
else if (numBytesToRead >= remainingBytes)
{ // it's time to get the remaining frame(s)
int totalBytes = remainingBytes + 6; // calculate total length
byte[] buffer = new byte[totalBytes];
byte[] remBuffer = new byte[remainingBytes];
// now reading remaining bytes as estimated using the frame header
// going altogether
sBuffer.readBytes(remBuffer, remainingBytes);
// tailoring bufhead and rembuffer into buffer
for (i = 0; i < totalBytes; i++)
{
if (i < 6)
{
buffer[i] = FrameHead[i];
}
else
{
buffer[i] = remBuffer[i - 6];
}
}
// now handling the message...
// checking terminator and CRC
ushort CRC = (ushort)(buffer[totalBytes - 2] + 256 * buffer[totalBytes - 1]);
if ((buffer[totalBytes - 3] == frameterminator) && (checkCRC(buffer, totalBytes - 2, CRC)))
{
EZFrame frame = bytes2Frame(buffer);
// done
if (frame.ReceiverID == NodeID) // packet addressed to this node
{
transitionAction(frame); // change internal state and act
}
}
// clearing remaining bytes
remainingBytes = 0;
}
numBytesToRead = sBuffer.bytesAvailable();
} while ((numBytesToRead >= remainingBytes) && (remainingBytes > 0));
}
// handling internal state according to input and triggering appropriate actions
public void transitionAction(EZFrame frame)
{
switch (state)
{
case stIdle: // not in process process of receiving or sending
if (frame.Ftype == t_Ping)
{ // received a ping frame. will acknowledge immediately...
sendAcknowledge(frame.SenderID);
state = stIdle; // state remains idle
}
else if (frame.Ftype == t_Acknowledge) // ignoring a random acknowledge
{
state = stIdle;
}
else
{ // any other type of frame
// now looking up the incomplete Packets Queue
EZStationPacketFSM incompletePack = findIncompletePacket(frame.SenderID);
if (incompletePack != null)
{
incompletePack.transitionAction(frame);
}
else
{ // adding a new incomplete pack
InsertNewIncompletePacket(frame);
}
state = stIdle; // still idle
}
break;
case stSending: // in the process of sending a packet. still, handling the incoming
if (frame.Ftype == t_Ping)
{ // received a ping frame. will acknowledge immediately...
sendAcknowledge(frame.SenderID);
state = stSending; // state remains stSending
}
else if (frame.Ftype == t_Acknowledge) // ignoring a random acknowledge
{
state = stSending; // keep on sending
}
else
{ // any other type of frame
// now looking up the incomplete Packets Queue
EZStationPacketFSM incompletePack = findIncompletePacket(frame.SenderID);
if (incompletePack != null)
{
incompletePack.transitionAction(frame);
}
else
{ // adding a new incomplete pack
InsertNewIncompletePacket(frame);
}
state = stSending; // still Sending
}
break;
case stWaitingAcknowledge: // expecting a frame reception acknowledgement
if (frame.Ftype == t_Ping) // casual ping. immediate reply
{
sendAcknowledge(frame.SenderID);
// state remains
state = stWaitingAcknowledge;
}
else if (frame.Ftype == t_Acknowledge)
{ // received and acknowledge frame
if (frame.SenderID == PacketReceiverID)
{
// increasing number of sent frames
FramesSent++;
if (FramesSent == TotalFrames)
{ // all sent
PacketReceiverID = 0;
state = stIdle;
}
else
{ // need to send more frames
state = stSending;
sendNextFrame();
}
}
else
{
state = stWaitingAcknowledge;
}
}
else
{ // assigning frame to proper Incomplete Packet recipient
// any other type of frame
// now looking up the incomplete Packets Queue
EZStationPacketFSM incompletePack = findIncompletePacket(frame.SenderID);
if (incompletePack != null)
{
incompletePack.transitionAction(frame);
}
else
{ // adding a new incomplete pack
InsertNewIncompletePacket(frame);
}
state = stWaitingAcknowledge; // still Waiting for acknowledge
}
break;
} // end big state switch
}