Building a custome IR remote control

[Mathew Clayson]

I would like to build a custom IR remote control using a picaxe. The remote is for LEGO. The LEGO company recently released the specs for it new IR power functions system. The RCX that LEGo sells is compatable with all of the IR codes. But the IR transmitter that they sell only supports momentary motor control, and I would like to use the PWM and single wire funtions as well.
http://philohome.com/pf/pf.htm
http://philohome.com/pf/LEGO_Power_Functions_RC.pdf

The hardware for this project seem very straight forward. It's the coding I'm unsure of. I've used the picaxe08m for several model train projects, and I'd like to use it here, but it may be lacking in code space. But it seems that coding all the bits in the contol code is beyond me, particually toggle and LRC bits.

If anyone has done something similar, I'd appreciate some pointers.

Mat

 

[hippy]

Difficult to say how easy or hard from a cursory glance at the PDF. Each bit starts with an IR burst ( 158uS using 38kHz ) but it's the time between pulses which defines the data and there seems to be some flexibility. The toggle bit is easy enough and the LRC simple to calculate. So basically build up an 18-bit packet, churn it out.

Times between IR bursts is 420uS upwards, and a PICAXE at 8MHz should be able to handle that.

I'm afraid there's not many pointers I've given to doing it and I'm a bit busy with other things at present but it might encourage others who may otherwise be a little daunted by the spec; I think it is possible.

Do you have access to an oscilliscope ? That would be very handy for verifying that what you think is being sent is being sent, and with the correct timing.

 

[Mathew Clayson]

Thanks, I guess it's time to roll up my sleeves and learn more about the programming ability of the picaxe devices.

I have access to an oscilliscope at work, so that will help.