i404USB.pl

The following Perl script sets the USB attributes. Before you execute it, make sure that it is talking to the right device. Furthermore, the script allows you to send and receive messages from the device. Say 'bye' if you don't want it.

#!/usr/bin/perl -w
use strict;
use POSIX qw(:termios_h);
use FileHandle; 

# syst:pass 12345
# syst:comm:term 1
# syst:comm:check 0

sub ascii_format
{
    my ($argin) = @_; 
    my $argout = ""; 
    foreach my $i ( 0 .. (length($argin) - 1))
    {
        my $let = substr( $argin, $i, 1); 
        my $dec = unpack( "C", $let); 
        if( $dec < 32)
        {
            if( $dec == 10){ $argout .= "<LF>";}
            elsif( $dec == 13){ $argout .= "<CR>";}
            else { $argout .= "<$dec>";}
        }
        else
        {
            $argout .= $let; 
        }
    }
    return $argout; 
}
my $buffer= " " x 200;
my ($nfd); 

#
# root> chmod 666 /dev/ttyUSB1
#
sysopen( I404, "/dev/ttyUSB0", O_RDWR) or die 'Failed to open /dev/ttyUSB0';

my $fd = fileno( I404); 
  
my $term = POSIX::Termios->new;     
$term->getattr( $fd);
#$term->setospeed( 4098);  # B115200
#$term->setispeed( 4098); 
$term->setospeed( &POSIX::B19200);  # B19200
$term->setispeed( &POSIX::B19200); 
my $lflag = $term->getlflag(); 
$lflag = $lflag & ~(&POSIX::ECHO); 
$lflag = $lflag | &POSIX::ISIG | &POSIX::ICANON | &POSIX::IEXTEN;
$term->setlflag( $lflag);  
my $c_cflag = $term->getcflag(); 
$term->setcflag( $c_cflag | &POSIX::CS8); 
$term->setcc( VMIN, 1); 

my $iflag = $term->getiflag(); 
$iflag = $iflag & ~(&POSIX::IXOFF); 
$iflag = $iflag | &POSIX::ICRNL | &POSIX::IXON; 
$term->setiflag( $iflag); 

my $oflag = $term->getoflag(); 
$oflag = $oflag | &POSIX::OPOST; 
$term->setoflag( $oflag); 
$term->setattr( $fd, &POSIX::TCSANOW);
my $len; 
my $argout = ""; 
print " enter 'bye' to exit \n";
while()
{
    print " Enter> ";
    $buffer = <>;  
    $buffer =~ s/^\s*(.*?)\s*$/$1/; 
    goto finish if( $buffer =~ /bye/i); 
    if( length( $buffer))
    {
        $buffer .= "\n"; 
        $len = syswrite( I404, $buffer, length( $buffer), 0);
        print " write $len bytes " . ascii_format( $buffer) . "\n"; 
    }
    $nfd = 1;
    while( $nfd)
    {
        my $rin = my $win = my $ein = ""; 
        vec( $rin, fileno( I404), 1) = 1; 
        $ein = $rin | $win;
        $nfd = select( $rin, $win, $ein, 1.);
        print " nfd $nfd \n";
        if( $nfd)
        {
            $buffer = "";
            $len = sysread( I404, $buffer, 100, 0);
            print " --- len $len " . ascii_format( $buffer) . "\n"; 
            if( $len) 
            {
                $argout .= $buffer; 
            }
            $buffer =~ s/^\s*(.*?)\s*$/$1/; 
            if( $len == 1)
            {
                last;
            }
        }
    }
}

finish:
close I404;