Let's Make Robots!

? Sending Serial Via IR?

So I read Frits's post about his little "data-in, data-out" RF doo-dads and it got me to thinkin'...

Can we send serial "pulses" (or high/low data in general) via IR using a picaxe? Now, I know that the picaxe chips have the "sony code IR" stuff built in and can use the irin command... Could I skip all this stuff and just set-up a data-in/ data-out system using IR? Would I use a IR transistor (2 pin) as a receiver or stick with the 3-pin unit? Also, when  the 3-pin IR reciever says "38khz" what does this mean? C'mon electronics geeks, gimme a schematic! I want a simple IR system where I can stick [serial] data in and get [serial] data out on the other end...

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This has been posted many times.

I know cptn tuna has posted on this.

http://letsmakerobots.com/node/2899

I've posted this image before showing the ir receiver I had worked on. It uses a 38khz modulated receiver(tsop34838) and minimal parts to build...I added the 3906 and green led to know when I received a signal. The rest was taken from the datasheet.

ir_complete_top_0.jpg 

 The transmitter side uses an ir emitter and a 3904 transistor. you just feed the collecter a pwm signal(modulated at 38.5khz) and send the base the serial output. hook up the emmiter to...well..the emitter...side and you have your transmitter setup. I've done this on a 08m. works like a charm. 

One advantage to using your own protocol might be speed. When I built my IR remote control using the sony protocol I found it was very slow. Too slow for what I intended.
I noticed when reading ir signals from a remote for my receiver(stereo not the ir one  :D) that it sent a group of values, like around 6 or so unique variables. maybe thats why it was slow? Just a thought as I found that interesting. 

Part of the problem is the low frequency of the carrier wave.

With the sony IR code, it sends 5 bits of data each time to specify device but since The IR input commands don't make use of this, it's wasted bits. I think the on/off times are also a bit long. I think they were after reliability over speed since an IR remote is not designed to send large volumes of data.

Admittedly if the on / off times are too short then not enough 38KHz pulses will get through to be recognised by the receiver as something other than noise. 

I need to experiment with using my own IR protocols as I would like to control 4 servos from my IR remote in something resembling real time.

Real time only exists in our minds... :D I dont think anything electronic happens in real time. :D

A humans concept of real time is completely different to a computers though.