linux-kernel - Re: [PATCH] favr32: improve touchscreen response

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Message-Id: <1246002577.9414.62.camel@linux-51e8.site>
Date:	Fri, 26 Jun 2009 17:49:37 +1000
From:	Ben Nizette <ben@...sdigital.com>
To:	"haavard.skinnemoen" <haavard.skinnemoen@...el.com>
Cc:	kernel <kernel@...32linux.org>,
	"Egtvedt, Hans-Christian" <Hans-Christian.Egtvedt@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] favr32: improve touchscreen response


Hi Haavard,

This has hce's ack, any chance of getting it in .31?

Thx,
	--Ben.

On Mon, 2009-04-20 at 12:36 +1000, Ben Nizette wrote:
> The ezLCD+101 board (to which an favr-32 is fitted) has a long,
> unshielded, nasty lead between the touch panel and the ads7843 touch
> controller.  In order to get satisfactory response then, we need to
> employ every noise-reduction trick in the driver's arsenal.  After
> extensive fiddling I've found some good settings:
> 
> 1) We keep vref on all the time to dramatically reduce settling times
> (at the cost of a tiny increase in power consumption).
> 
> 2) Despite 1 the settling time is still non-zero.  500uS is plenty of
> time for the signals to settle
> 
> 3) Despite 1 and 2 there's still a little bit of noise around.  By
> setting a pen recheck delay we make the panel feel less touchy and
> twitchy.
> 
> Someone with more time and patience myself might be able to tune this
> numbers further but these settings are now perfectly acceptable for
> normal use.
> 
> Tested on ezLCD+101 though should only improve response on other ezLCD+/
> favr-32 boards too.
> 
> Signed-off-by: Ben Nizette <bn@...sdigital.com>
> 
> ---
>  arch/avr32/boards/favr-32/setup.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/avr32/boards/favr-32/setup.c b/arch/avr32/boards/favr-32/setup.c
> index 58203d1..f1152fa 100644
> --- a/arch/avr32/boards/favr-32/setup.c
> +++ b/arch/avr32/boards/favr-32/setup.c
> @@ -72,6 +72,10 @@ static struct ads7846_platform_data ads7843_data = {
>  	.debounce_max		= 20,
>  	.debounce_rep		= 4,
>  	.debounce_tol		= 5,
> +	
> +	.keep_vref_on		= true,
> +	.settle_delay_usecs	= 500,
> +	.penirq_recheck_delay_usecs = 100,
>  };
 

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