fgetl hangs reading serial port

On 12-Apr-2005, R. Bruce Madigan <bmadigan@xxxxxxxxx> wrote:

| To: bug-octave@xxxxxxxxxxxxxxxxx
| Cc: bmadigan
| Subject: fgetl hangs reading serial port
| --------
| Bug report for Octave 2.1.40 configured for i386-redhat-linux-gnu

2.1.40 is really quite old (that snapshot was made almost 2-1/2 years
ago).  The current recommended version is 2.1.69.

| I cannot read data from a serial device from within octave.  I establish
| communication with the device using minicom and am able to send and
| receive.  I exit minicom (with minicom configured to do nothing to the
| port when it exits) and run the following program:
| 
| [fid,msg]=fopen("/dev/ttyS0","r+","native")
| cmdstr=setstr([0x41,0x54,0x0d,0x00])
| fputs(fid,cmdstr)
| sleep(1);
| fgetl(fid)
| fclose(fid)
| 
| The program hangs at fgetl.

That's probably because Octave uses blocking I/O by default.

| I have used the procedure on two different
| computers and talked to two different devices.  (The example above is
| talking to a modem, sending "AT" and expecting "OK").  I am sure the
| command string (cmdstr) is reaching the serial device because I can see
| a change of status on the serial device ( for example the send data and
| reveive data lights on the modem blink).

The following works for me with a recent version of Octave:

  octave:22> f = fopen ("/dev/ttySL0", "r+")
  f =
  {
    id = 3
    name = /dev/ttySL0
    mode = r+b
    arch = ieee_little_endian
    status = open
  }
  octave:23> fcntl (f, F_SETFL, O_NONBLOCK)
  ans = 0
  octave:24> fputs (f, "AT\n")
  ans = 0
  octave:25> fgetl (f)
  ans = AT
  octave:26> fgetl (f)
  ans =
  octave:27> fgetl (f)
  ans = OK
  octave:28> fgetl (f)
  ans = -1
  octave:29> fputs (f, "AT\r")
  ans = -1
  octave:30> fclear (f)
  octave:31> fputs (f, "AT\r")
  ans = 0
  octave:32> fgetl (f)
  ans = AT
  octave:33> fgetl (f)
  ans = OK
  octave:34> fgetl (f)
  ans = -1
  octave:35> fclose (f)
  ans = 0

jwe



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