Post by thread:[PIC]: IR protocols

Dear Wan Hasmi, Wan Hasmi <spam_OUTwhasmiTakeThisOuTVISCON.PO.MY> on 2001-04-05 08:20:53 PM wondered: > Subject: Re: [PIC]: Sample serial data ... > I connect the output from the IR module to one of the PIC > I/O pin and monitor the pulse ... > how do we differentiate which key was pressed if we sample > the I/O pin on PIC? ... There's a lot of links to IR communcation protocols (and a few schematics) at rdrop.com/~cary/html/machine_vision.html#communication ftp://ftp.armory.com/pub/user/rstevew/IR/ . Most cheap "TV remotes" transmit a ``1'' by turning on and off the LED at 40 KHZ, and transmit a ``0'' by keeping it turned off. They send bits at about 2 Kbit/s. If you have the right hardware to "demodulate" the 40 KHz signal, your PIC only needs to sample at maybe 4000 samples/s (is that right ?). Once you press a button on a remote, it keeps sending out the same bit pattern over and over until you let it up. Some of them alternate between 2 different bit patterns for the same button -- so that when you hold down the "channel up" button, the TV goes up only one channel, until you release and press it again, giving the *other* channel up code that allows the TV to go to the next channel. (Um, does this need to move to the [EE]: topic ?) -- David Cary -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu