From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vignesh R <vigneshr@ti.com>
Subject: Re: [PATCH 1/4] input: touchscreen: ti_am335x_tsc Interchange touchscreen
 and ADC steps
Date: Mon, 10 Nov 2014 16:16:22 +0530
Message-ID: <5460977E.9060604@ti.com>
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To: Richard Cochran <richardcochran@gmail.com>
Cc: Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>, Mark Rutland <mark.rutland@arm.com>, Ian Campbell <ijc+devicetree@hellion.org.uk>, Kumar Gala <galak@codeaurora.org>, Benoit Cousson <bcousson@baylibre.com>, Tony Lindgren <tony@atomide.com>, Russell King <linux@arm.linux.org.uk>, Jonathan Cameron <jic23@kernel.org>, Dmitry Torokhov <dmitry.torokhov@gmail.com>, devicetree@vger.kernel.org, Lars-Peter Clausen <lars@metafoo.de>, Samuel Ortiz <sameo@linux.intel.com>, Jan Kardell <jan.kardell@telliq.com>, linux-iio@vger.kernel.org, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Felipe Balbi <balbi@ti.com>, Paul Gortmaker <paul.gortmaker@windriver.com>, Peter Meerwald <pmeerw@pmeerw.net>, Hartmut Knaack <knaack.h@gmx.de>, linux-omap@vger.kernel.org, Lee Jones <lee.jones@linaro.org>
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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
>