Control IR input socket on receiver from pimatic

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I have a NAD receiver, the NAD T752, this has an IR receiver port on the back. It would be nice if I could use this port to control the receiver, e.g. change input source, increase/decrease volume etc.

I found a hardware interface which can connect to this port:
http://www.massey.ac.nz/~jcmarsha/hometheatre/remote_extender.shtml

I think it should be possible to adapt the interface to be controlled by the gpio port of the Raspberry PI. Unfortunately my electronics skills have faded away since I left uni about 20 years ago.

Could anyone guide me in the right directions on how to adapt the circuit to be controlled by the GPIO? Maybe replacing the IR receiver in the schematic with an optocoupler should suffice?

That should definitely be possible someway. I have a NAD C370 which I want to control remotely as well. Not sure whether it is going to be controlled by pimatic or by Volumio, but I surely have been thinking about this. I think the remote in/outputs are quite the same? I can’t promise you too much, but I’ll try to see if I can dive into this somewhere the next coming weeks.

there are ready made ir extender, won’t they work?

just to give some examples :

http://de.aliexpress.com/item/New-Arrival-1-25m-Infrared-IR-TV-Remote-Control-Receiver-Extender-Cable-Wire-Adapter-Black/32606168037.html

http://de.aliexpress.com/item/Wholesale-Price-Hight-Quality-Black-300cm-Dual-IR-Infrared-Emitter-Cable-with-3-5mm-Plug-Remote/32597574951.html

Edit - ah ok, sorry, now i got it … you want to use the ir port to control the receiver with pimatic.
well isn’t that a little inconvenient?
you could build a simple ir transmitter with this little hardware setup
https://forum.pimatic.org/topic/235/howto-receive-transmit-infrared/

or if you have the raw codes, you can also use ESPimatic to send IR signals.
so you could have a ir/wifi solution. just my two cents on that.

I would like to use the IR port because it’s a direct connection to the receiver internals, thus hopefully a more stable connection. Also a separate IR transmitter needs to be placed in view of the IR receiver of the device, thus in front of the device. I like to keep a clean look of the HiFi setup, and an IR transmitter in front of the setup is not my definition of a clean look.

I just found these instructions on how control NAD Link from the Raspberry PI:
https://github.com/tsprlng/nad-link

However the connector on my NAD receiver is labeled IR, and not NAD Link, so I’m not sure if these are the same kind of interface.

Oh wow, this is such a great library: my C370 does have the NAD-link I did some research a while (>2yrs) ago but did not find an actual complete implementation, so I was preparing to do it all myself. Gotta love open source

For your IR port: it is probably the same signal, though maybe inverted or with voltage levels which need to be converted to be suitable for the RasPi. Though the IR extender in your link works with 5V, so possibly its easy.
I think you should be able to control it from the RasPi with just a simple level shifter in between. These are available in cheap ICs or you can build them yourself with a few FETs and resistors.

Well, the circuit on the first site I referred to contains a 555 timer to create a carrier frequency, but still I think a lot of the circuit can be discarded and the carrier frequency could maybe even be generated by the raspberry pi. A simple transistor level shifter then does the trick

Here you can find more commands you could use in the NAD Link script:
http://lirc.sourceforge.net/remotes/nad/SR6

As far as I understand you indeed do need to modulate the signal. Don’t know if Lirc maybe is already capable of doing this, otherwise you could use an NE555 or a small uController.

I guess you should be able to use Lirc in gpio mode and instead of connecting an IR LED (which you could for testing) just connect the port of your receiver.

Maybe you need to add a transistor (+matching resistors) as according to the link in the first post the port expects 5v TTL level and the PI is on 3v3.

I would try to controll it via the LED and GPIO and if this works wire it up to the port. If this doesn’t work I would try to convert TTL level with the help of the transistor to 5v.

Yes, it looks a lot easier than I first expected as Lirc is als doing the modulation. Going to order parts and let you know if it works!

Just a quick message that I have the IR input socket on my NAD receiver working, will explain later in more detail. It was really easy!

As promised some more details.

First I installed LIRC following these instructions:
http://alexba.in/blog/2013/01/06/setting-up-lirc-on-the-raspberrypi/

I did not configure the gpio_in_pin as I’m not using an IR receiver.

I connected GPIO 22 to the center pin (tip) of a 3.5mm jack plug and ground to the outside and connected the cable to the IR-in of my NAD T752

I used codes from this file for the lircd.conf file
http://lirc.sourceforge.net/remotes/nad/SR6

From the command line everything worked immediately. The NAD receiver is happy with the 3.3 volt signal it gets, no problems.

The LIRC plugin for pimatic is a different story, very buggy, and breaks your pimatic rules when its unable to initialise properly. I have to dive into the LIRC plugin and improve it, but have to find some time to do so. I will create a new topic on the LIRC plugin later when I’ve made the required changes.

So all in all the hardware side of the installation was a piece of cake, software wise I’m not yet satisfied.