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Logging Serial Ports with Mojolicious

by haukex (Bishop)
on Mar 19, 2020 at 20:37 UTC ( #11114488=CUFP: print w/replies, xml ) Need Help??

I gave a talk recently at the German Perl Workshop in Erlangen (video here, in German). In that talk, among other things, I spoke about how I built a data logger for a sensor, and was doing everything with Mojolicious - reading the serial port, logging the data, and providing a user interface. Since it may be a little bit until I can publish the design of the data logger, I've put together a stripped-down example in case it's useful to someone. The key pieces here are:

It's a relatively long piece of code, but it's entirely self-contained. If you have any questions or suggestions, please feel free to let me know!

#!/usr/bin/env perl use 5.028; use Mojolicious::Lite -signatures; use Mojo::IOLoop::Stream::Role::LineBuffer; use Mojo::SQLite; use Mojo::JSON qw/encode_json/; use Mojo::Util qw/dumper/; use Fcntl qw/:DEFAULT/; use IO::Termios (); # NOTICE: This script is designed to work in a single-threaded, # single-process server only! (morbo or Mojolicious::Command::daemon) # disable template cache in development mode (e.g. under morbo): app->renderer->cache->max_keys(0) if app->mode eq 'development'; helper sql => sub { state $sql = Mojo::SQLite->new(':memory:') }; app->sql->migrations->from_string(<<'END_MIGRATIONS')->migrate; -- 1 up CREATE TABLE DataLog ( Timestamp DATETIME, Source TEXT, ValueA TEXT, ValueB TEXT ); -- 1 down DROP TABLE IF EXISTS DataLog; END_MIGRATIONS my %serports = ( # this is essentially the configuration for the ports '/tmp/fakepty1' => sub { sysopen my $fh, '/tmp/fakepty1', O_RDONLY or die "sysopen /tmp/fakepty1: $!"; my $hnd = IO::Termios->new($fh) or die "IO::Termios->new: $!"; $hnd->set_mode('19200,8,n,1'); #use IO::Stty; # if needed #IO::Stty::stty($hnd, qw/ cs8 -parenb raw -echo /); return $hnd; }, '/tmp/fakepty2' => sub { sysopen my $fh, '/tmp/fakepty2', O_RDONLY or die "sysopen /tmp/fakepty2: $!"; my $hnd = IO::Termios->new($fh) or die "IO::Termios->new: $!"; $hnd->set_mode('19200,8,n,1'); return $hnd; }, ); my $retry_interval_s = 10; my $parse_re = qr{ ^ (?<Source> \w+ ) , (?<ValueA> \d+ ) , (?<ValueB> \d+ ) $ }msx; my $serial = Mojo::EventEmitter->new; # serial event dispatcher sub setup_streams { state %streams; for my $k (sort keys %serports) { next if $streams{$k}; my $handle = eval { $serports{$k}->() }; if (!$handle) { $serial->emit(error => "Stream $k Open: $@"); Mojo::IOLoop->timer($retry_interval_s => \&setup_streams); next; } $streams{$k} = Mojo::IOLoop::Stream->new($handle) ->with_roles('+LineBuffer')->watch_lines; $streams{$k}->on(read_line => sub ($strm, $line, $sep) { if ( $line =~ $parse_re ) { my %rec = ( %+, Timestamp => time ); app->sql->db->insert('DataLog', \%rec); $serial->emit(data => \%rec); } else { $serial->emit(error => "Stream $k: failed to parse ".dumper($line)) } }); $streams{$k}->on(close => sub ($strm) { $serial->emit(error => "Stream $k Closed"); $streams{$k}->stop; delete $streams{$k}; Mojo::IOLoop->timer($retry_interval_s => \&setup_streams); }); $streams{$k}->on(error => sub ($strm, $err) { $serial->emit(error => "Stream $k Error: $err"); }); $streams{$k}->on(timeout => sub ($strm) { $serial->emit(error => "Stream $k Timeout"); # could possibly close & re-open stream here }); $streams{$k}->start; } } Mojo::IOLoop->next_tick(\&setup_streams); get '/' => sub ($c) { $c->render(template => 'index') } => 'index'; get '/q' => sub ($c) { $c->render(template => 'query') } => 'query'; get '/events' => sub ($c) { $c->inactivity_timeout(300); $c->res->headers->content_type('text/event-stream'); $c->write; my $cb_data = $serial->on(data => sub ($ser,$data) { my $json = encode_json($data) =~ s/\n//gr; $c->write("event: ser_data\ndata: $json\n\n"); } ); my $cb_err = $serial->on(error => sub ($ser,$err) { $err =~ s/\n//g; $c->write("event: ser_err\ndata: $err\n\n"); } ); $c->on(finish => sub ($c) { $serial->unsubscribe(data => $cb_data); $serial->unsubscribe(error => $cb_err); }); } => 'events'; app->start; __DATA__ @@ index.html.ep % layout 'main', title => 'Hello, World!'; <nav>[ <b>Live</b> | <%= link_to Query => 'query' %> ]</nav> <main> <div><table border="1"> <tr> <th>Source</th> <th>Timestamp</th> <th>ValueA</th> <th>ValueB</th> </tr> <tr> <th>Foo</th> <td id="Foo_time">-</td> <td id="Foo_vala">-</td> <td id="Foo_valb">-</td> </tr> <tr> <th>Bar</th> <td id="Bar_time">-</td> <td id="Bar_vala">-</td> <td id="Bar_valb">-</td> </tr> </table></div> </main> <script src="https://code.jquery.com/jquery-3.4.1.min.js" integrity="sha256-CSXorXvZcTkaix6Yvo6HppcZGetbYMGWSFlBw8HfCJo=" crossorigin="anonymous"></script> <script> "use strict"; var events = new EventSource('<%= url_for 'events' %>'); events.addEventListener('ser_data', function (event) { var data = JSON.parse(event.data); $('#'+data.Source+'_time').text(data.Timestamp); $('#'+data.Source+'_vala').text(data.ValueA); $('#'+data.Source+'_valb').text(data.ValueB); }, false); events.addEventListener('ser_err', function (event) { alert(event.data); }, false); </script> @@ query.html.ep % layout 'main', title => 'Query'; <nav>[ <%= link_to Live => 'index' %> | <b><%= link_to Reload => 'query' %></b> ]</nav> <main><table border="1"> % my @fields = qw/ Timestamp Source ValueA ValueB /; <tr> % for my $f (@fields) { <th><%= $f %></th> % } </tr> %# NOTE: This database code doesn't normally belong in the view % my $results = sql->db->select('DataLog', % \@fields, undef, ['Timestamp','Source']); % while ( my $row = $results->hash ) { <tr> % for my $f (@fields) { <td><%= $row->{$f} %></td> % } </tr> % } </table></main> @@ layouts/main.html.ep <!DOCTYPE html> <html> <head><title><%= title %></title></head> <body> %= content </body> </html>

This is the script to provide the fake serial ports using socat:

#!/usr/bin/env perl use warnings; use strict; use Data::Dump; use IPC::Run qw/ start /; print STDERR "Starting...\n"; my @procs = ( { n=>'Foo', c=>['socat','pty,rawer,link=/tmp/fakepty1','-'], v=>sub { "Foo,".(time-$^T).",".int(rand(100))."\n" } }, { n=>'Bar', c=>['socat','pty,rawer,link=/tmp/fakepty2','-'], v=>sub { "Bar,".(time-$^T).",".int(rand(100))."\n" } }, ); for my $p (@procs) { $p->{i} = \(my $i=''); $p->{o} = \(my $o=''); $p->{p} = start $p->{c}, $p->{i}, $p->{o}; } print STDERR "Running...\n"; my $run = 1; local $SIG{INT} = sub { print STDERR "Caught SIGINT\n"; $run = 0 }; while ($run) { for my $p (@procs) { sleep 1; ${$p->{i}} .= $p->{v}->(); $p->{p}->pump; if ( length ${$p->{o}} ) { dd $p->{n}, ${$p->{o}}; ${$p->{o}} = ''; } } } $_->{p}->signal('INT') for @procs; $_->{p}->finish for @procs; print STDERR "Done.\n";

To run this code, first start the second script (e.g. perl fakeports.pl), and then the first, e.g. via morbo serlogger.pl, and then visit the URL shown in the console. (Note this won't work on Windows.)

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