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Created May 26, 2014 22:43
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Perl program which talks to the Agilent U1272A found on
#! /usr/bin/perl
# Proof of concept for Mac <-> Agilent U1272A communications
# Copyright (c) 2011 M J Oldfield <>
# Version 0.1 2011-06-17 M J Oldfield
use strict;
use warnings;
package My::U1272;
use Time::HiRes qw(time);
sub new
my ($class, $trace, $b19200) = @_;
my $port = $class->get_portname;
my $dev = Device::SerialPort->new($port)
or die "Unable to open $port, ";
print "Opened $port :)\n";
$dev->baudrate($b19200 ? 19200 : 9600);
return bless { dev => $dev, trace => $trace, t0 => time() }, $class;
sub get_portname
my ($port, @others) = glob "/dev/tty.PL*";
die "No device found, " unless $port;
die "Multiple devices, " if @others;
return $port;
sub trace
my $s = shift;
return unless $s->{trace};
my $t = sprintf "%0.3f ", time() - $s->{t0};
print $t, @_, "\n";
# Execute a simple command and read back the result, assuming that there's one line
# terminated by "\n". Chop the line terminators off the response
# Assuming that $ignore_err isn't true, if we get an error ('*E') back ask why
sub cmd
my ($s, $cmd, $ignore_err) = @_;
my $dev = $s->{dev};
$dev->write($cmd . "\n");
$s->trace(">: $cmd");
my $response = '';
my ($count, $txt) = $dev->read(1);
next unless $count;
$response .= $txt;
last if $txt eq "\n";
$response =~ s/[\n\r]+$//;
$s->trace("<: $response");
if ($response eq "*E" && !$ignore_err)
my $err = $s->cmd('SYST:ERR?');
print "Error detected: $err\n";
return $response;
# A bunch of SCPI commands which the meter understands
sub identity { shift->cmd('*IDN?') }
sub battery { shift->cmd('SYST:BATT?'); }
sub config { shift->cmd('CONF?'); }
sub reading { shift->cmd('FETC?'); }
sub reading2 { shift->cmd('FETC? @2'); }
# Read the log
sub get_log
my ($s, $log) = @_;
my $cmd = "LOG:$log %d";
my @log;
print "Grabbing $log log:";
my $i = 1;
if ($i % 1000 == 1) { printf "\n %4d: ", $i - 1; }
elsif ($i % 100 == 1) { printf "."; }
my $res = $s->cmd(sprintf($cmd,$i), 1);
last if $res eq '*E';
# This is, quite frankly, a guess at the decoding!
my ($pre, $data, $post) = ($res =~ /^"(\d{2})(\d{5})(\d{6})"$/)
or die "Can't parse reading $i : $res\n";
push(@log, [ $i, $data, $pre, $post ]);
print "\nFinished\n";
return \@log;
package main;
use Getopt::Long;
use YAML qw(Dump DumpFile);
use Device::SerialPort;
use Pod::Usage;
$| = 1; # unbuffer stdout
my %Opt;
GetOptions(\%Opt, "help!", "info!", "trace!", "19200!", "get_log=s", "cmd=s");
pod2usage(-verbose => 2)
if $Opt{help} || $Opt{info};
my $dev = My::U1272->new($Opt{trace}, $Opt{19200});
if (my $cmd = $Opt{cmd})
my $res = $dev->cmd($cmd);
print "$res\n";
elsif (my $log = $Opt{get_log})
my $file = lc($log) . ".txt";
die "Dumpfile $file already exists and I refuse to overwrite it.\n"
if -f $file;
my $data = $dev->get_log($log);
open(my $fh, '>', $file) or die "Couldn't open $file: $!\n";
print {$fh} map { sprintf("%5d %6d %6d %6d\n", @$_) } @$data;
my $n = @$data;
print "$n data from $log log written to $file\n";
my %data;
foreach my $k (qw(identity battery config reading reading2))
no strict 'refs';
$data{$k} = $dev->$k;
print Dump(\%data);
=head1 NAME
u1272a - A toy application which talks to a U1272A
=head1 USAGE
$ u1272a
$ u1272a --trace
$ u1272a --trace --cmd='*IDN?'
$ u1272a --get_log=AUTO
A toy application which talks to an Agilent U1272A DMM over Agilent's
IR interface cable.
This is really just a proof of concept, so you shouldn't rely on its
reliability or functionality.
=head1 OPTIONS
By default the program just queries a bunch of data and prints it. You can change:
=item --help, --info
Display this page.
=item --trace
Print the low-level communications with the meter.
=item --19200
Talk to the meter at 19200 baud (the default is 9600).
=item --cmd=foo
Execute the foo command and print the (one-line) result.
=item --log=AUTO|HAND
Retrieve logged data from the meter. This barely works: it's slow
(roughly one minute per thousand points), and I don't really
understand the format.
The software assumes that there's precisely one device of the form
/dev/tty.PL* and that said device is the meter you're trying to prod.
We also assume that the meter is set to 9600 baud, 8-bit, no-parity,
and 1 stop-bit (the meter's default settings). If you want to try the
giddy speeds of 19200 baud use the --19200 option.
The meter settings can be changed in the meter's setup mode: see
Agilent's User Manual.
All the serial stuff is done via Device::SerialPort.
It seems moderately likely that I'm not using that module optimally.
This program is a quick hack: it is not production quality code. In
most cases no parsing of the data from the meter is done; logged data
are parsed, but the algorithm is just a guess.
The serial port interface should be about three times faster.
Please report problems to the author.
Patches are welcome.
=head1 AUTHOR
M J Oldfield,
Copyright (c) 2011, M J Oldfield
This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself. See L<perlartistic>.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
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