Re: serial communication

I'm having a problem with my serial communication, the following function
is
executed in a thread.

int KissLayer::readSerial()
{
KissLayer * kissobj = KissLayer::instance();
lock lck(kissobj->monitortimeout, false);
std::vector<UCHAR> receivedmes;
//parsen
UCHAR receivedstat; //bit 0: begin bericht ontvangen
//bit 1: einde bericht ontvangen
//bit 2: ACK ontvangen
//bit 3: WACK ontvangen (niet in gebruik)
//bit 4: NACK ontvangen (niet in gebruik)
//bit 5: ESC ontvangen
//bit 6: IGNORE ESC (aka mss framenumber)
//bit 7: CRC bezig
receivedstat = 0x00;

while (kissobj->fcontinue)
{
UCHAR charac;
if (!kissobj->serial.ReadByte(charac))
{
//ICR Timeout
if (receivedstat > 0)
{
std::cout << "clear all ic timeout or nothing received" << std::endl;
//ic timeout, nack sturen als het niet over ACK gaat
if ((receivedstat & 0x04)==0)
{
UCHAR ackbytes[1];
ackbytes[0] = 0x15;
kissobj->sendData(ackbytes, 1);
}
//alle buffers leegmaken
receivedstat = 0x00;
receivedmes.clear();
}
}
else
{
//put solution here

if ((receivedstat & 0x02)!=0)
{
if ((receivedstat & 0x80)!=0)
{
receivedmes.push_back(charac);

bool crcok = false;

std::vector<UCHAR> message;
message.assign(receivedmes.begin(), receivedmes.end());
UCHAR seqnum = message[1];

std::cout << "end message number:" << std::hex <<
int(static_cast<unsigned char>(seqnum)) << std::endl;

if ((seqnum == 0xFF) || (seqnum == kissobj->externalframenumber + 1) ||
(seqnum == 0x00 && kissobj->externalframenumber == 0xFF) || (seqnum ==
kissobj->externalframenumber) || kissobj->syncing)
{

kissobj->helper.decapsulateKiss(message, &crcok);
if (crcok)
{
kissobj->helper.unEscapeVic(message);

//zelfde nummer als vorige = negeren!
if (seqnum != kissobj->externalframenumber)
{
std::cout << "data naar vic laag sturen" << std::endl;
kissobj->singlebuffer->pushkiss(message);
}

//ack versturen
UCHAR ackbytes[2];
ackbytes[0] = 0x06;
ackbytes[1] = seqnum;
kissobj->sendData(ackbytes, 2);
}
else
{
kissobj->helper.unEscapeVic(message);
//crc niet goed, nack sturen
UCHAR ackbytes[1];
ackbytes[0] = 0x15;
kissobj->sendData(ackbytes, 1);
}

//ok: volgende bericht
kissobj->externalframenumber = seqnum;
kissobj->syncing = false;
}
else
{
//desync probleem: VIC layer waarschuwen zodat een cancel verstuurt
kan worden en de buffer kan geleegd worden
//TODO: applicatie verwittigen
std::cout << "sync_probleem";
}

//alle bits afzetten
receivedstat = 0x00;
//buffer vrijmaken
receivedmes.clear();
}
else
{
//crc bit aanzetten
receivedstat = receivedstat ^ 0x80;
receivedmes.push_back(charac);
}
}
//is er een ack
else if ((receivedstat & 0x04)!=0)
{
UCHAR acknumber = charac;
std::cout << std::hex << "ack nummer: " << std::hex <<
int(static_cast<unsigned char>(acknumber)) << std::endl;
if (acknumber == kissobj->framenumber)
{
kissobj->waitingforanswer = false;
//alle bits afzetten
receivedstat = 0x00;

if (kissobj->framenumber < 0xFF) kissobj->framenumber++;
else kissobj->framenumber = 0x00;

//volgende bericht
kissobj->bufferkiss_send_next.notify_one();
}
}
//is er een escape
else if ((receivedstat & 0x20)==0 || (receivedstat & 0x40)!=0)
{
switch(charac)
{


default:
//ignore bit afzetten
receivedstat = receivedstat & 0xBF;
receivedmes.push_back(charac);
}
}
else //er was een escape
{
//escape afzetten
receivedstat = receivedstat^0x20;
receivedmes.push_back(charac);
}
}
}

return 0;
}

the readbyte function called in the above function looks like this

bool CSerialPort::ReadByte(UCHAR &resp)
{
BYTE rx;
resp=0;

DWORD dwBytesTransferred=0;

if (HasOverlappedIoCompleted(&ovRead))
{
ReadFile (hComm, &rx, 1, &dwBytesTransferred, &ovRead);
}

if (!GetOverlappedResult(hComm, &ovRead, &dwBytesTransferred, TRUE))
return
false;

if (dwBytesTransferred == 1)
{
resp=rx;
return true;
}

return false;
}

The timeout for the serial read is 2 ms. Now the problem is, everything
goes
fine until the last character is received. At that moment the output would
be
something like

clear all ic timeout or nothing received
end message number: <some number>

But when I debug the line
if ((receivedstat & 0x02)!=0)
is hit before the Inter character timeout code part. After that it jumps
to
the inter character timeout code and then back to message parsing code.
This
ofcourse gives problems because at that point my vector buffer is being
emptied and read at the same time so i only got a part of my message to
parse. It looks like the function is being executed twice, how is this
possible?

A solution I came up with is putting the thread to sleep for a short time
on
the line where the comment "//put solution here" shows. However I don't
like
that solution and it still doesn't give me an understanding of the
problem. I
hope I explained the problem adequate enough. Could somebody please help
me?