Christmas with Elmo

I wasn't expecting to get much done on Elmo over the Christmas period because we had family visiting. Having mentioned my IR transmitter problems to Dad, an ex-BBC electronic engineer, he came up with a lot of good advice and we spent a happy morning fiddling with the Elmo breadboard and troubleshooting his ideas for a signal amplifier.

During the process, I discovered that, unlike most mobile phone cameras, my iPhone 5 doesn't pick up IR very well. We were using the camera to see when the IR transmitter was working and were getting rather baffled as to why nothing seemed to be coming out of the transmitter. Switching to Mum's old Nokia phone and the IR transmitter lit up like a Christmas tree and we knew we had the right approach.

Some more fiddling and highly technical walking backwards and forwards holding a Sky box to test the range and we'd fine tuned the components to give a good range of IR transmission - certainly plenty for now. What a great result.

There is a Mark 2 circuit to come, but for now, here's the schematic we've ended up with:

All credit goes to Dad for the IR transmitter. Now I'm set to continue development.

LIRCing

Finally had some time to spend on Elmo and after a fair bit of fiddling have got LIRC working. There seems to be something a bit odd about the GPIO pin configuration for the receiver and transmitter, but I eventually managed to find a combination that would work and I can now successfully, and consistently, read codes from an IR remote control

Transmitting has proved a little more problematic. I can get my normal LEDs to work straight from the GPIO pins, but the IR transmitters won't work (you can't see the IR they give out with the naked eye, but you can use a phone camera to see the pulses). I believe the devices need too high a current.

This is something I foresaw and so got some transistors, however I didn't get the correct resistors and I don't want to risk overloading the Pi, so I'll hold off until I've had chance to get some more resistors

In the meantime, I've also set up a technical blog - mostly for my own use because otherwise I tend to lose the scraps of paper I jot things on.

Open Source Joy

Having spent days trawling all manner of RPi forums, blogs, help sites and such, I have finally managed to get lirc operational on the Raspberry Pi.

Almost all of the sites missed at least one step needed, which led me to become incredibly frustrated - especially when I'm running the 'preferred' RPi distro - Raspbian - which has recently had the LIRC support built into it. My problem turned out to be the firmware. Installing the firmware update tool and running that eventually got me where I needed to be - and the mode2 lirc test program now happily outputs lots of lovely, raw, IR data when I fire my remote into the receiver.

Unfortunately, that's eaten all my available time for this weekend, so it'll be another week before I have a chance to do any more ... at least it's progress, though.