Date: Sat, 17 Jun 2000 18:56:12 +0100 (BST) From: Andrew Gordon <arg@arg1.demon.co.uk> To: Nate Lawson <nate@elite.net> Cc: freebsd-hardware@freebsd.org Subject: Re: LCD panel/buttons Message-ID: <Pine.BSF.4.21.0006171809180.7128-100000@server.arg.sj.co.uk> In-Reply-To: <Pine.BSD.3.91.1000616165943.19992B-100000@almond.elite.net>
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On Fri, 16 Jun 2000, Nate Lawson wrote: > > Also, we hope to add an IR remote. I was looking at the keyspan.com USB > unit that maps IR to keystrokes. This seems like a good thing but it's > also a bit pricey. Has anyone used the IR port on PC motherboards to > have a universal remote device for FreeBSD? Any other suggestions would > be great. "IR port on PC motherboards" generally means IRDA. If you had in mind a TV-style remote to be used across the width of a room, IRDA is useless: it uses a very crude modulation scheme (pulse = 0, no pulse = 1) and so it has very short range (about 1m) and requires sender/receiver to be pointing directly at each other. TV remotes typically use a more robust coding scheme, modulating a carrier of 38KHz or 56KHz. I have done RC5 (one of the popular encoding schemes) on FreeBSD by bashing bits on a parallel port - driving an IR LED for transmit, and using one of the integrated receiver devices (eg. Sharp IS1U60: photodiode, amplifier, detector, integrator all in a 3-pin package for < $1) for reception. However, this is all a bit too fast to do reliably in software - for receive you need to time pulses that are nominally 888us or 1778us wide. For serious applications, I use a PIC12C508 to offload the real-time stuff - still only a total component cost of about $2. As well as TV-type remotes, you can get qwerty keyboards using similar modulation schemes that you can receive on the same hardware; these have slightly less range/robustness (higher datarate -> shorter pulses), but still work OK. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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