How to identify the protocol of IR Remote (infrared Remote)?

Question

I have an setup of Raspberry pi 3 Model B v1.2 and I have installed LIRC (Linux Infrared remote control) to send and receive IR signals (using an IR receiver and transmitter) from the raspberry pi.

Now my question is, How do I identify the protocol of the IR remote ? ex: NEC/RC5/RC6/SIRC.

Your help is much appreciated. Do comment below if any other information is required.

U can try this to detect the protocol use: https://github.com/bengtmartensson/IrScrutinizer https://github.com/probonopd/irdb — user1757800, Dec 21 '22 at 11:24

wes · Answer 1 · 2023-07-14T23:14:10.820

I just found my remote's protocol by following these steps. You don't need LIRC specifically, just the kernel's rc_core support.

I enabled the IR receiver on my Raspberry Pi by adding the overlay in config.txt:

dtoverlay=gpio-ir,gpio_pin=17 # substitute with your pin number

Reboot and then confirm your receiver has been added:

# dmesg | grep 'rc '
[    7.985963] rc rc0: gpio_ir_recv as /devices/platform/ir-receiver@11/rc/rc0
[    7.994038] rc rc0: lirc_dev: driver gpio_ir_recv registered at minor = 0, raw IR receiver, no transmitter

My receiver is rc0. Remember this for later!
Find your receiver's input in /dev/inputs

# ls -l /dev/input/by-path/
total 0
lrwxrwxrwx 1 root root 9 Apr 28  2022 platform-fe9c0000.xhci-usb-0:1.1:1.0-event-kbd -> ../event0
lrwxrwxrwx 1 root root 9 Apr 28  2022 platform-ir-receiver@11-event -> ../event1

You'll need a program to check if the input is working. I tested the input with this simple perl script, but the principle will work in any language:

#!/usr/bin/perl

use strict; use warnings;
use Fcntl 'O_RDONLY';

my $file = '/dev/input/event1'; # YOUR IR INPUT HERE
sysopen(my $fh, $file, O_RDONLY) or die "no file: $!";
binmode($fh);

while (1) {
    my $count = sysread($fh, my $data, 24);
    my ($sec, $usec, $type, $code, $value) = unpack('L<L<S<S<l<', $data);
    print "$sec.$usec\n";
    printf "   type: %02x\n", $type;
    printf "   code: %02x\n", $code;
    printf "  value: %08x\n", $value;
}

Now we can start testing protocols. You can change the set protocol by writing to the sysfs node for your IR input (mine is rc0):

# cd /sys/class/rc/rc0
# cat protocols                                                                                                                
rc-5 nec [rc-6] jvc sony rc-5-sz sanyo sharp mce_kbd xmp imon [lirc]

Now we just work through them one by one and press buttons on the remote until we see some action:

# echo 'rc-5' > protocols 
# cat protocols 
[rc-5] nec rc-6 jvc sony rc-5-sz sanyo sharp mce_kbd xmp imon [lirc]
# ~/read-input.pl
(no output)

No dice, let's keep trying.

# echo 'nec' > protocols 
# cat protocols 
rc-5 [nec] rc-6 jvc sony rc-5-sz sanyo sharp mce_kbd xmp imon [lirc]
# ~/read-input.pl
1689373948.890804
   type: 04
   code: 04
  value: 00860514
1689373948.890804
   type: 00
   code: 00
  value: 00000000

Looks like my remote speaks NEC protocol!

Now let's make sure it always has the right protocol set at boot time with a udev rule (Mine is rc0):

# cat /etc/udev/rules.d/ir-input.rules 
ACTION=="add", KERNEL=="rc0", SUBSYSTEM=="rc", RUN+="/bin/sh -c 'echo nec > /sys/class/rc/rc0/protocols'"

Now my remote works after a reboot.

Notes

I don't know why lirc is always enabled in the protocol list, but it doesn't seem to interfere.
Input struct format is from the Linux input docs via this excellent go demonstration.

How to identify the protocol of IR Remote (infrared Remote)?

1 Answers1

Notes