USB/Serial port weirdness

richardrosa · 2026-04-14 20:12:17

Greetings All,

Recently I migrated my system to Arch Linux from SUSE.

It appears that everything is working Ok EXCEPT serial/USB port processing with PERL.

I have a PERL script that communicates with various radios using the USB ports.
The routine makes use of the Device::SerialPort library.

This library was installed via PACMAN.

In ARCH, this routine is unable to communicate with any attached radio.

After a LOT of investigation,
it appears that the issue is with the baud rate setting.

I wrote a small PERL script to test this out.

Using the library to set baudrates, then issuing 'stty' to get the actual baud rate set,
I got the following results:
$portobj->baudrate(9600) stty=> 13 baud
$portobj->baudrate(19200) stty=> 14 baud
$portobj->baudrate(38400) stty=> 15 baud
$portobj->baudrate(57600) stty=> 4096 baud
$portobj->baudrate(115200) stty=>4098 baud

Very strange.

For some additional tests:
Tried this test with another radio.
Same incorrect results.

Ran this script on an ARCH distro on a different machine.
Same incorrect results.

Built a Linux Mint OS on a different partition on the same machine.
The correct baud rates were set.

This does NOT appear to be hardware related.

I attempted to bypass this issue using 'stty -F {port} {baudrate}
This kind of helped a bit.
However, one of the radios I am communicating with requires binary data (00x-ffx).
For some reason, the binary data is also changing the baud rate.
I've verified this by issuing a 'stty -F {port}' after a transmission.

I took a quick look at the SerialPort library routine, and it has not been
updated since 2009. It also appears to be identical (using a compare routine) to the version in SUSE.

Is there some additional setting or application that is needed?

The Kernel version is 6.19.11-arch1-1), and I am running KDE X11.

I've included the code snippet used to test:

  
#!/usr/bin/perl
use strict;
use Device::SerialPort qw( :PARAM :STAT 0.07 );
my $port = '/dev/ttyUSB1';   ### Current port of radio

my $portobj =  Device::SerialPort->new($port) ;
if (!$portobj) {
   print "Could not get port object for $port!\n";
   exit;
}
$portobj->user_msg('ON');
$portobj->databits(8);  
$portobj->handshake('none'); 
$portobj->parity("none");
$portobj->stopbits(1);
$portobj->read_const_time(100); 
$portobj->read_char_time(5);    

foreach my $bd ('9600','19200','38400','57600','115200') {
   $portobj->baudrate($bd);
   print "Baud=>$bd\n";
   system "stty -F $port";
}
exit;

Thanx for any help.

Richard Rosa

seth · 2026-04-14 20:25:42

Sounds like https://bbs.archlinux.org/viewtopic.php … 4#p2261294 though that's supposed to be fixed in glibc 2.43

Arch Linux

#1 2026-04-14 20:12:17

USB/Serial port weirdness

#2 2026-04-14 20:25:42

Re: USB/Serial port weirdness

Board footer