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RE: Serial Port Problems



Hi there,

I have been experiencing some problems interfacing the serial ports on two seperate systems: a windows 2000 PC and a windows XP laptop. Basically, all I want to do is read some data from a device that is connected to the serial port.

I am using some code (that works under linux) to open the serial port (/dev/ttyS0) as read-only and read the incoming data. The setup of the baud rate and flags seems to go smoothly, yet the program hangs on the read() function. However, I know that data is arriving because HyperTerminal shows that it is there.

stty gives some interesting results:

$ stty -F /dev/ttyS0
speed 0 baud; line = 0;
intr = <undef>; quit = <undef>; erase = <undef>; kill = <undef>; eof = <undef>;
swtch = <undef>; susp = <undef>; rprnt = <undef>; werase = <undef>;
lnext = <undef>; flush = <undef>; min = 0; time = 0;
-cread
-brkint -icrnl -imaxbel
-opost -onlcr
-isig -icanon -iexten -echo -echoe -echok -echoctl -echoke


as well as:

$ stty -F /dev/ttyS0 -a
speed 0 baud;stty: /dev/ttyS0: Function not implemented


Not sure if this is normal (a zero baud rate?). The same results occur on both systems. Anyway, I have found a few posts that look somewhat similar to my problem:


  http://www.cygwin.com/ml/cygwin/1998-12/msg00695.html
  http://www.cygwin.com/ml/cygwin/2002-01/msg00062.html
  http://www.cygwin.com/ml/cygwin/2003-07/msg01312.html

But no solutions posted.

Any suggestions/comments would be greatly appreciated.

You can configure your serial port -attached file-desc to return after one single byte or after a timeout by configuring the appropriate members of the struct termios -member <c_cc>. Read http://www.easysw.com/~mike/serial/serial.html for details.


;Henning



--
H. Henning Schmidt
email: henning@hhschmidt.de
phone: +49 (0) 6155 / 899 283
fax:   +49 (0) 6155 / 899 284


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