linux-kernel - Re: Toggling GPIO at 38Khz

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Message-ID: <m363o292b9.fsf@maximus.localdomain>
Date:	Wed, 08 Oct 2008 23:58:34 +0200
From:	Krzysztof Halasa <khc@...waw.pl>
To:	"Jon Smirl" <jonsmirl@...il.com>
Cc:	"Bill Gatliff" <bgat@...lgatliff.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> writes:

> These are external boards people buy to use with MythTV. They are most
> commonly used on the x86, but the NSLU2 has been modified to use them
> too.
>
> The hardware can't be changed, people have bought thousands of these devices.
>
> Many people cut up a serial cable and solder it themselves...

Sure but you only need to bit-bang at 36 or so kHz while transmitting,
right? The receive side is a slow one as the receiver chip has an
integrated "demodulator".

If so then personally... I'd abandon the simple TX circuit, and use
a hardware ~36 kHz oscillator, gated by the serial output signal.
I don't think such transmitters are in thousands. Tens, maybe - the
cost of replacing/modifying them all should be insignificant. I guess
one could design and produce such a TXer in less than 20 minutes.
-- 
Krzysztof Halasa
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