HWe
New User
Jan 19, 2013, 8:28 AM
Post #1 of 2
(510 views)
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Beginner problem with serial /dev/ttyS0 on linux
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Hi,
I have a perl-script (see attached) that is suppposed to read and write single bytes from the serial port /dev/ttyS0. But it does'nt work as expected.
It was used successfully by others already. I also searched google and other forums for a solution - not solution found yet !
I can receive single bytes easily using Python-scripting or a terminal like "putty" or "minicom" - the serial port works !
But with the below perl-script it does not work. Here is the first part of the script, supposed to work (full script find attached):
#!/usr/bin/perl
system("stty -F /dev/ttyS0 speed 19200");
open(COM, "+</dev/ttyS0") || die("Can't Open ttyS0 for reading");
open(OUT, ">/dev/ttyS0") || die("Can't Open ttyS0 for writing");
$cmd = "";
$sent = "";
$state=0;
$data = "";
$picmode = 0;
$jpeg_stream=0;
while(1==1){ #$res=getc(COM)){
$res=getc(COM);
$val = ord($res);
$cmd .= $res;
if (substr($cmd,0,1) ne "A"){ $cmd = ""; }
print "<$res\n"; #enbled by HWE
printf ("%02x = %c\n",$val, $val);
.... and so on ....
I also tried the following on my own:
#!/usr/bin/perl
use Device::SerialPort;
my $COM = new Device::SerialPort("/dev/ttyS0");
$COM->databits(8) || die("error databits");
$COM->baudrate(19200) || die("error baudrate");
$COM->parity("none") || die("error parity");
$COM->stopbits(1) || die("error stopbits");
$COM->handshake("none") || die("error handshake");
$COM->write_settings || die("error writesettings");
my $buffer;
while (1) {
read( PORT, $byte, 1 );
$buffer .= $byte;
if ( length( $buffer )) {
printf( "Buffer now has %d bytes; last byte read was 0x%02x\n",length( $buffer ), $byte );
}
}
But it does not work either.
How can I tell perl to receive single bytes from the serial port ?
Why does the above script not work.
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