After several years' use it's time to retire our Teac DR-H300DAB DVD receiver. As part of the re-vamp of our home AV system, I'm going to cannibalise the hefty mains transformer and the class D power amp circuit board from it.

The new setup will use a Lumagen Radiance AV switcher/scaler and I'll take its coax SPDIF to the rebuilt power amp. I'll need to convert SPDIF to analogue stereo of course, and this will be followed by a volume control stage (with loudness correction permanently applied) and a mute switch.

For simplicity I'll probably use a motorised volume control and the plan is to use a Somfy IRT 103 remote to "up/down" the volume and "stop" (mute) the audio.

I've found the codes for the IRT 103 on remotecentral.com but, at this early stage, am not yet sure how to process the IR sensor's output to - in effect - replicate the button presses on the remote. If anyone into IR remote control can give me a "steer" I'd appreciate it - there's bound to be a chip that's ideally suited to this task, I'd have thought.

I'll need to have the remote's stop button effect a toggle operation for the mute, otherwise the design should be straightforward - once I've decoded the commands coming from the remote.

This of any help to you?

Ooh, yes - thanks djy; this and the related FPRC5RX article are very helpful.

Yesterday I e-mailed Somfy to ask about the IRT 103 protocol, but haven't heard back yet.

Hopefully it'll turn out to be one of those supported by the FPRC5RX, such as the Philips RC5 or Sony Sircs.

Anyone know for sure?

From the doc (decodeIR.html) supplied with DecodeIR.dll, the IRP form for Somfy is:
{35.7k}<308,-881|669,-520>(2072,-484,F:2,D:3,C:4,-2300)+
C is reported as SubDevice. It is probably a check nibble {C = F*4 + D + 3}.
F = 1 for UP or 2 for DOWN.
D = 1, 2 or 3 for the three observed devices, or D = 0 to control all devices together.

This is not a standard IR protocol, and is a very limited one at that: only 4 possible function numbers, with up to 8 devices. Makes sense for controlling curtains and screens. I'll be surprised if you find any available IC that can decode this.

Of course, Somfy could be using a different protocol in the IRT 103.

Any reason for using this remote other than the presumably small number of buttons? Most any universal can send standard protocols, even the $5 ones with a limited number of buttons.

Thanks 3FG, and yes, it was the small number of buttons - ie just the three required - and the non-specific legending on the IRT 103 (which can be interpreted as volume up; volume down; mute) which attracted me.

If you know of something similar which uses standard protocols... but hey, I just thought: I could always re-engineer the IRT 103's innards and replace with something which will send the three commands using the Philips RC-5 protocol. I've years of experience laying-out and producing my own small PCBs, after all: see [Link: flickr.com]

So, now maybe it's a case of finding a chip for a basic RC-5 IR transmitter.