stuart wrote: > > Tom Metro wrote: >> stuart wrote: >>> Humm, but I can't find what I'm thinking of (using a 74CH00 chip, >>> half as a monostable multi vibrator operating at 40KHz and the other >>> half to help gate the signal). >> That might be because the modulation required by some devices may be >> more sophisticated than simple asynchronous amplitude modulation. Some >> devices may require frequency or phase modulation, or AM that is >> synchronous with the carrier wave. >> >> Although according to: >> http://www.linux.org/docs/ldp/howto/Infrared-HOWTO/infrared-howto-c-lirc-irda.html >> >> "The IrDA Physical Layer is totally incompatible with the DASK >> modulation used in IR remote controls." > > Yeah, if I recall right ... irda (like on a Palm Pilot) is a bunch of > pulses where I think 0s and 1s are marked by either having or not having > a pulse. Ask is more like pulses of ~40KHz modulated light. I would > guess irda is generally faster but only works over a short distance > whereas ask is slow but can be filtered (@ ~40KHz) so can work over > longer distances. (The accuracy of the above is questionable as I'm > being lazy and not looking anything up. (i.e. [needs citation])) > >> I assume the D in DASK stands for digital. Amplitude-shift keying (ASK) >> is described here: >> http://en.wikipedia.org/wiki/Amplitude-shift_keying >> >> and in its simplest form would be achievable with the circuit you describe. >> >> This site: >> http://www.zen22142.zen.co.uk/Circuits/Interface/mod_det.htm >> >> which has a schematic for building an IR receiver for use with a scope >> for observing remote control signals (most likely overkill, and with a >> decent scope you'd do fine with a photodiode or a phototransistor and a >> few components), also backs up the idea that the modulation is simple AM. >> >> That site also has a pile of remote control extender circuits: >> http://www.zen22142.zen.co.uk/Circuits/Interface/rce.htm >> >> which could be adapted for use with a PC. >> >> >>> Instead I found things like: >>> http://www.lirc.org/improved_transmitter.html >>> ...which need each pulse controlled as you said above. >> And half of that circuit is just trying to achieve creating a power >> source for the LEDs from the serial port. If you wired up a power >> supply, you could probably do it with half the components. > > Yes, I noticed that too. Consider that if you did load up the Palm > Pilot w/the code to produce ASK that (reportedly) you need to be w/in a > few feet of the receiver for it to work. So having enough power is > important. (Point your *digital* camera at your remote control. It's > quite bright.) This all begs the question: "At that distance, why not > just reach out and use you hand?". > >>> ...I'd search the hifi-remote.com web site. Chances are very good >>> that someone has already captured the codes you are interested in and >>> published them... >> Agreed. I wouldn't recommend using a scope to reverse engineer the >> actual codes. I was just suggesting using it to verify that the general >> signal characteristics, such as modulation frequency and type, match >> between the original remote and the simulated remote. >> >> -Tom > > I think it's time (where does that stuff come from any ways?) to try > some things out on the work bench. Regardless, I think I'll add some of > your links to the hardwarehowto along w/some possible mvpmc > enhancements. I've always thought an IR blaster on the mvpmc box would > be nice (i.e. Get rid of the TV remote!). > >
Ok, added this to the mvpmc hardware howto: http://www.mvpmc.org/mvpmc_hardware_howto.html#s11 ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Mvpmc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/mvpmc-users mvpmc wiki: http://mvpmc.wikispaces.com/
