I have an issue.. Trying to figure out a way for a device I'm working on to do it's thing while keeping an eye out (using a IR photoTransistor) for any given simple 555 based IR transmitters (beacon) and triggering some code when it sees one...

Basically, there will be some simple IR Beacons that consist of a 555 (or 3909, etc.) blinking an IR LED (or three) at 10hz or so...roaming around... My mBed device (in a stationary position) will be running some code to manage it's hardware...all the while polling or using an interrupt, or whatever works best to trigger some code when one of these beacons comes into range of the mBed's IR photoTransistor..

My problem is that I haven't figured out how to get it to recognize only the 10hz signal... I'd love it if I could even see more than one (not necessarily simultaneously) and distinguish them from each other... Like some that run at 10hz and some that run at 50hz or something... The same problem could be in reverse where an mBed based robot roams around searching for a IR Beacon Base Station.....if that helps envision the problem..

Any suggestions would be greatly appreciated!!

Don't know how much published info you can find on it, but that is the way that the iRobot Roomba vac finds the charger.