Building a remote control

I own a Yamaha RX-461 AV receiver. It's old, but still working fine, except that the remote control is broken. I don't want to buy a new receiver just because the remote broke, but a working remote is the only way to access the setup menu, which is quite unfortunate. I tried to order replacement remotes, but all of them would only work partially. In particular, not a single one allowed me to access the setup menu.

So I decided, I've got to build my own remote control. Conveniently, I still have a Raspberry Pi laying around. All I needed to get was an infrared emitter for it. I decided for the Open-Smart emitter because that one just needs to be connected to Raspberry Pi. But you can certainly get the IR-LED, resistors, and a transistor to assemble the control circuit yourself. This is the wiring:

Initial configuration

We then need to setup the Raspberry Pi to be able to send IR codes via the emitter. We will be using lirc for that, so go ahead and install it.

sudo apt install lirc

Next we add the required kernel modules to be loaded during system boot. Add the following lines to /etc/modules:

lirc_dev
lirc_rpi gpio_out_pin=24

We also need to adjust the lirc configuration itself in /etc/lirc/lircd.conf by editing the corresponding lines:

[lircd]
driver = default
device = /dev/lirc0

In the /boot/config.txt, we need this line:

dtoverlay=gpio-ir-tix,gpio_pin=24

Configuring the remote

Now we have the basic configuration of the hardware, but we also need to configure the specific remote control commands, we want to send. But for that we need to know these. Usually, one would record these from an existing remote with an IR receiver. However, this is not an option for me as the old remote does not work anymore. Luckily, I found out (somewhere on the Internet) that Yamaha is using the NEC protocol, and I found this helpful documentation how the protocol works. So all I had to do, was to translate this into a lirc configuration in /etc/lirc/lircd.conf.d/yamaha-rx-v461.lircd.conf:

begin remote

    name RX_V461
    bits 32
    flags SPACE_ENC|CONST_LENGTH

    gap 108000
    zero 563 562
    one 563 1687
    header 9000 4500
    ptrail 563

    toggle_bit_mask 0x0

    begin codes
        # Add command codes here.
        # What are these, though? 🤔
    end codes

end remote

To be able to send actual commands, we need the codes for those commands, though. Here I got lucky again, and found a forum with a large collections of files for all sorts of hi-fi devices. Among those files is a "Yamaha Master File" which contains a bunch of PDFs with remote control codes for different Yamaha receivers. Lo and behold, the Yamaha RX-V461 is among them! The code for "set menu", for example, is given as 7A-84. Now, in the NEC protocol, each byte is followed by the bitwise inverse (presumably to always have a constant transmission length), so the full command code should be 7A-85-84-7B. However, this did not work.

The final piece to the puzzle fell into place reading some obscure forum post. The bit-order needs to reversed! So 7A becomes 5E, for example, or the whole command code would be 5E-A1-21-DE. When putting it into the configuration it becomes:

begin remote

    # The stuff from above goes here

    begin codes
        SET_MENU 0x5EA121DE
    end codes

The other codes follow the same principle. The full configuration can be found here.

Sending IR commands

Reboot the Raspberry Pi after all those configuration changes to ensure the latest settings are loaded. You can send a single command like this:

irsend SEND_ONCE RX_V461 SET_MENU

If you need to check, that the IR transmitter is sending anything at all, a cell phone camera comes in handy (use the front camera if you're using an iPhone). The IR flashes should be visible on it.

If you want to send a command repeatedly, use SEND_START and SEND_STOP instead of SEND_ONCE.