linux-kernel - Re: IR raw input is not sutable for input system

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Message-ID: <m34ooi7cb5.fsf@intrepid.localdomain>
Date:	Wed, 25 Nov 2009 18:18:38 +0100
From:	Krzysztof Halasa <khc@...waw.pl>
To:	Trent Piepho <xyzzy@...akeasy.org>
Cc:	Maxim Levitsky <maximlevitsky@...il.com>,
	Jarod Wilson <jarod@...sonet.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Jarod Wilson <jarod@...hat.com>, linux-kernel@...r.kernel.org,
	Mario Limonciello <superm1@...ntu.com>,
	linux-input@...r.kernel.org, linux-media@...r.kernel.org,
	Janne Grunau <j@...nau.net>,
	Christoph Bartelmus <lirc@...telmus.de>
Subject: Re: IR raw input is not sutable for input system

Trent Piepho <xyzzy@...akeasy.org> writes:

> The signal recevied by the ir receiver contains glitches.  Depending on the
> receiver there can be quite a few.  It is also not trivial to turn the raw
> signal sent by the remote into a digital value, even if you know what to
> expect.  It takes digital signal processing techniques to turn the messy
> sequence of inaccurate mark and space lengths into a best guess at what
> digital code the remote sent.

This is of course true. Except that most receivers do that in hardware,
the receiver/demodular chip such as TSOP1838 does it.
If you receive with a phototransistor or a photodiode feeding some sort
of ADC device (not a very smart design), sure - you have to do this
yourself.

I have never heard of such receiver, though.

> One thing that could be done, unless it has changed much since I wrote it
> 10+ years ago, is to take the mark/space protocol the ir device uses and sent
> that data to lircd via the input layer.  It would be less efficient, but
> would avoid another kernel interface.  Of course the input layer to lircd
> interface would be somewhat different than other input devices, so
> it's not entirely correct to say another interface is avoided.

IOW, it would be worse, wouldn't it?
-- 
Krzysztof Halasa
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