TinyCore Raspberry Pi minimal USB RFID reader or USB barcode reader to MQTT gateway

setup-pi-mqtt-rfid-keyboard-wedge-gateway.sh

# Have an old Pi that would corrupt its SD cards with normal Pi OS's, so used TinyCore linux for pi instead
# which only writes to SD card when you run `filetool.sh -b` ... basically it's become more like a 
# embedded microcontroller that posts to MQTT when a tag or barcode is scanned.

# after following the tinycore pi setup instructions and getting its networking going, I
tce-load -wi ntp
tce-load -wi perl5
tce-load -wo cpanm
echo /usr/local/bin/ntpdate time.chu.nrc.ca >> /opt/bootlocal.sh
echo /usr/local/bin/ntpd >> /opt/bootlocal.sh
cpanm Net::MQTT::Simple

# install stuff to run "instead of" the normal console.  Use flock so only one copy runs
echo >> ~tc/.ashrc 'flock -n /dev/shm/gateway perl -Iperl5/lib/perl5 gateway.pl'

# this currently relies on my mqtt broker publishing the time every second, and updates
# a watchdog entry every ten seconds.  Without that, might be better to just do a loop around tick()
# instead of using run()

cat > gateway.pl <<EOF
use Net::MQTT::Simple;
use IO::Select;

$b=Net::MQTT::Simple->new("mqtt-broker.example.com");
$b->last_will("rfids/pi","down",1);

$s = IO::Select->new();
$s->add(\*STDIN);

$b->run("time/seconds"=>sub{
  my $t=time();
  if ($s->can_read(.5)) {
    chomp($tag = <STDIN>);
    $b->publish("rfids/$tag",$t);
  } elsif ( substr($t,-1) == '0' ) {
    $b->retain("rfids/pi",$t);
  }
});
EOF

sudo mount /mnt/mmcblk0p1
# add consoleblank=0 to /mnt/mmcblk0p1/cmdline.txt
# otherwise the screen saver will kick in and block keystrokes

filetool.sh -b
sudo reboot
# you should see the gateway watchdog update in MQTT and entries for each thing scanned