linux-kernel - Re: Toggling GPIO at 38Khz

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Message-Id: <E1KnXwl-0006JX-EF@be1.7eggert.dyndns.org>
Date:	Wed, 08 Oct 2008 14:15:19 +0200
From:	Bodo Eggert <7eggert@....de>
To:	Jon Smirl <jonsmirl@...il.com>,
	ARM Linux Mailing List 
	<linux-arm-kernel@...ts.arm.linux.org.uk>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: Toggling GPIO at 38Khz

Jon Smirl <jonsmirl@...il.com> wrote:

> I'm working on getring the LIRC IR subsystem integrated into the
> kernel. One common IR hardware implementation is based on standard
> serial ports. It uses the serial port's DCD and DTR as GPIO pins.
> This common IR hardware does not have a transmit modulator and is
> modulating the IR signal in software. Luckily is has hardware
> demodulation.
> 
> There are four common IR frequencies - 36Khz, 38Khz, 40Khz, 56Khz. I
> need to create these frequencies in software. Data is then transmitted
> as 400-600us burst of these frequencies. Around 10-30 clock pulses.
[...]

The ALSA PC-Speaker sound driver might do something similar ...

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