serial port communication woes
First post... done a ton of googling to try and figure out my problem, to no avail. Hopefully this is the right forum.
I'm talking over an RS232 to a motion control board. I've got a windows library that I ported to Linux to make it talk serial to said board. Commands to the board work great... I can move motors and do all kinds of fun stuff. However, getting data back through the board is not working so great.
What happens is the high bit of every byte is 0, regardless of if it should be or not. The problem manifested itself when trying to get the position of the motor back... if it is at 127, it is fine, but when it should return 128, it send back 0.
After opening, the code to configure looks like this:
Code:
tcgetattr(hPeriph->handle, &options);
//Set up baud rates
cfsetispeed(&options, baudList[baud]);
cfsetospeed(&options, baudList[baud]);
//Enable the receiver and set local mode...
options.c_cflag |= (CLOCAL | CREAD);
options.c_cflag &= ~(PARENB| PARODD);
//Set up stop bits
options.c_cflag &= ~CSTOPB;
//Disable HW flow control
options.c_cflag &= ~CRTSCTS;
//Setup input parity processing
options.c_iflag &= ~(IGNBRK | BRKINT | ICRNL |
INLCR | PARMRK | INPCK | ISTRIP | IXON);
options.c_oflag = 0;
options.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN | ISIG);
tcsetattr(hPeriph->handle, TCSANOW, &options);
I've tried dozens of combinations with the various parameters, to no avail. The baud rate is correct (57600), and it is 8N1.
The windows code from the vendorworks fine, here is the config for that:
Code:
dcb.DCBlength = sizeof(DCB);
dcb.BaudRate = baudList[baud];
dcb.fBinary = 1;
dcb.fParity = TRUE;
dcb.fOutxCtsFlow = 0;
dcb.fOutxDsrFlow = 0;
dcb.fDtrControl = DTR_CONTROL_DISABLE;
dcb.fDsrSensitivity = 0;
dcb.fTXContinueOnXoff = 0;
dcb.fOutX = 0;
dcb.fInX = 0;
dcb.fErrorChar = 0;
dcb.fNull = 0;
dcb.fRtsControl = RTS_CONTROL_DISABLE;
dcb.fAbortOnError = 0;
dcb.XonLim = 0;
dcb.XoffLim = 0;
dcb.ByteSize = 8;
dcb.Parity = parList[parity];
dcb.StopBits = stopList[stopbits];
dcb.XonChar = 0;
dcb.XoffChar = 0;
dcb.ErrorChar = 0;
dcb.EofChar = 0;
dcb.EvtChar = 0;
if( !SetCommState( hPeriph->handle, &dcb ) )
return FALSE;
return TRUE;
Thoughts? I know that the data coming back from the board is the same regardless of windows/linux is talking to it (scoped the line), so I've got to think it is my setup or some weird driver issue.
serial port communication woes
Hi Medvedm,
I'm not an expert with serial line things and tend to fight to get them working to be honest. It sure sounds like a stop bit problem but your stop bits look good for 8N1.
Would you mind trying this?:
Code:
tcgetattr(hPeriph->handle, &options);
// Set terminal to raw mode
cfmakeraw( &options ); // <-- New line
//Set up baud rates
cfsetispeed(&options, baudList[baud]);
cfsetospeed(&options, baudList[baud]);
#ifdef DISABLED
XXX/Enable the receiver and set local mode...
XXXoptions.c_cflag |= (CLOCAL | CREAD);
#endif
options.c_cflag &= ~(PARENB| PARODD);
//Set up stop bits
options.c_cflag &= ~CSTOPB;
#ifdef DISABLED
XX//Disable HW flow control
XXoptions.c_cflag &= ~CRTSCTS;
XX
XX/Setup input parity processing
XXoptions.c_iflag &= ~(IGNBRK | BRKINT | ICRNL |
XX INLCR | PARMRK | INPCK | ISTRIP | IXON);
XX
XXoptions.c_oflag = 0;
XXoptions.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN | ISIG);
#endif
tcsetattr(hPeriph->handle, TCSANOW, &options);
