linux-kernel - Re: [PATCH 1/4] input: touchscreen: ti_am335x_tsc Interchange touchscreen and ADC steps

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Message-ID: <5460977E.9060604@ti.com>
Date:	Mon, 10 Nov 2014 16:16:22 +0530
From:	Vignesh R <vigneshr@...com>
To:	Richard Cochran <richardcochran@...il.com>
CC:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Benoit Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	Jonathan Cameron <jic23@...nel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	<devicetree@...r.kernel.org>, Lars-Peter Clausen <lars@...afoo.de>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Jan Kardell <jan.kardell@...liq.com>,
	<linux-iio@...r.kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	<linux-input@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Felipe Balbi <balbi@...com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Peter Meerwald <pmeerw@...erw.net>,
	Hartmut Knaack <knaack.h@....de>, <linux-omap@...r.kernel.org>,
	Lee Jones <lee.jones@...aro.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Brad Griffis <bgriffis@...com>
Subject: Re: [PATCH 1/4] input: touchscreen: ti_am335x_tsc Interchange touchscreen
 and ADC steps



On Friday 07 November 2014 01:30 PM, Richard Cochran wrote:
> On Fri, Nov 07, 2014 at 11:04:05AM +0530, Vignesh R wrote:
>>
>> Currently, there is too much noise in the TSC hardware that is being
>> removed by delta filtering.
> 
> The so called "filter" was only programmed because the fifo entries
> were being mixed up. Sebastian fixed that.
> 
>> I tested TSC unit by removing filtering
>> logic, the performance was not at all satisfactory. The cursor jumps
>> wayward and smooth circles cannot be drawn. Looks like delta filtering
>> cannot be removed as of now. May be I will try and address it in future.
> 
> The "filter" code is nonsensical. It picks the two values in seqeunce
> that are closest to one and another. How is that supposed to work?
> 
> Did you look at the "noise"? What kind of properties did you see?
> 
> A median filter makes more sense. Or sort, remove outliers, and
> average. But choosing the two closest in series is silly.

I was able to implement median filter as you described and achieve
reliable performance. I will append that to this series of patches in v3.

Regards
Vignesh

> 
> Thanks,
> Richard
> 
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