[mythtv-users] USB dual channel IR blaster?

Travis Tabbal travis at tabbal.net
Mon Feb 22 20:18:20 UTC 2010

> +2 for a dual channel device. Possibly only +0.5 for a single channel
> device.
> What might a device like this look like on the transmitting side? Is
> it an external USB device? Plugs into any USB slot? Has two ports on
> it to hook up to two IR transmitter devices? What IR transmitters
> would you support so I can check out the costs on those? Can I use
> multiple devices if I want to control more than 2 STBs?
> I'd certainly pony up a little money (say $25-$50) to help with your
> initial PCB costs, etc. I assume that if and when I works I get at
> least a 2-channel device to own, etc.
> As an alternative a 2 or 4 channel 1x PCI-Express card for internal
> use might be of interest if you already know of an appropriate
> microcontroller and want to go that way.

It could be made to meet all your requirements. Internal USB headers are a
possibility, but they don't seem to be 100% standardized like the external
plugs are. As for transmitter devices, they are nothing more than an IR LED
on a stick with a mono 1/8" jack on the end for the most part. Just about
anything would work in that case. I could easily drive about 8 of them
without issue, possibly with different signals for all 8. Once one of them
works, it's really not a big deal to add more. You could even build your own
if you wanted to, though I know I've seen these things pretty cheaply out
there on the net. irblaster.info has them for about $6, they look to be the
same as the ones Smarthome sells.

PCIe is a real pain to talk to. USB is far easier and significantly cheaper
to interface to for this level of project. We don't need the bandwidth, so
there's no reason to deal with the problems, IMO.

I'm willing to do the hardware and firmware as an OSS project if others want
to contribute either funds or code. The biggest code help that would be nice
is someone to write the LIRC driver. It's going to take me some time to get
that part working if I have to do it myself. Or is there an easier way to
get Myth talking to it? The simplest method to do the firmware I can think
of right now is to make it look like a serial port to the computer, so you
just open /dev/ttyS0 or whatever the device name is and send it commands
like "SEND CH1 <IR timing string>". We could even toss a receiver in while
we're at it. May as well cover all the bases. It shouldn't be hard to be
very competitive with the existing products price wise with the parts I have
in mind, and it would be OSS, so no need to worry about binary drivers and

If there are a few interested people out there, please contact me directly
so we don't clutter the list. I can probably knock up a prototype on the
bench pretty quick. PCBs will take a little time to be made after I can
verify correct operation.
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