Building a Linux Media Network, one step at a time

Saturday, February 25, 2006

IR Remote Control and LIRC

LIRC is a Linux utility that allows input from many common types of remote controls. It integrates very nicely with XMMS, the media player I've chosen to install on Fulcrum.

The LIRC website has a bunch of instructions on how to build your own homebrew IR receiver that hooks up to a standard serial port. From what I understand, it's not "true" serial communication as all the data is transferred over one of the handshake lines, but everything seems to work out OK.

The schematic that I used is here. I ordered all the parts from Digikey, except the breadboard, which I got from a local electronics store. And the case, which is an Altoids tin.

Here's the Digikey parts list:

Digikey Part #Description
PNA4602M-NDInfrared photoreciver + IC
AN78L05-NDVoltage Regulator
P974-NDCapacitor - 4.7 uf 25V
P4.7KBACT-ND4.7 kilo-ohm resistor
C3APT-1018M-NDIDC Cable

Some notes:

  • Digikey charges a substantial service fee for orders under $35 (CAD). So if there's anything else you need, tack in onto the order. Pick up a few of the voltage regulators and a couple of the IR receivers in case anything goes sideways. Digikey also sells several similar receivers (PNA4612M00YB-ND, PNA4612M00XD-ND) with metal holders, which may help reduce interference.

  • I can't say for sure that the diode I've listed above is correct. I made a mistake and got the surface-mount casing; but I checked the catalog and that looks like the right one.

  • The pinouts on the IR receiver (substitute for the TSOP1738 in the schematic) and the voltage regulator are different than the ones described on the LIRC homebrew instruction page. As that page suggests, double-check that you've got them wired correctly.

  • One end of the IDC cable I specified above is a perfect fit for the serial header on the SP800 motherboard. The other end can be munged a little bit to fit into a 0.1" printed circuitboard on an angle. Since I had to visit the local electronics shop anyways, I picked up a proper IDC 16 pin crimp connector and used that instead.

  • Total costs were $33.60 to Digikey + ~= $10.00 to the local electronics shop. Definitely more practical to pick up a Windows Media Centre remote + USB receiver (which I believe is compatible with LIRC), but not nearly as much fun.

Assembling the circuit is actually really easy, and I say that as someone with very little experience in electronics. I'd suggest wiring it up on a solderless breadboard first, especially if you are as unfamiliar with this sort of thing as I was. Once you're comfortable with how everything hooks together, it's then just a challenge of laying it out on the breadboard with as little soldering as possible.

This is pretty much how I laid it out on the final breadboard, although I stretched it out a little bit to give myself some more room to work:

This is a picture of the final product with the case open:

I added the case (a butchered Altoids Mints container) because I was trying to resolve some interference problems. These problems only arose while I was working on this at the office, not at home. The case didn't actually resolve the problem, but I'm not too worried about it.

Finally, an up-to-date picture of Fulcrum. The Altoids case is closed in the picture. Notice that I have attached a proper momentary contact switch, so I don't have to short the jumpers with the needlenose pliers. That was fun for a while but got tiring. Notice also that the ghetto piece of plywood has been replaced with a ghetto piece of 1/16" sheet steel. However, that piece of steel was taken from a damaged Cray XD1, so I think I score some geek points for that.

That covers the hardware. Next up, building and configuring the software.


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