Touchscreen filters in andy-tracking...

Nelson Castillo arhuaco at
Wed Jan 28 15:24:46 CET 2009

On Wed, Jan 28, 2009 at 4:17 AM, Andy Green <andy at> wrote:
> Hash: SHA1
> Somebody in the thread at some point said:
> | On Tue, Jan 27, 2009 at 8:05 PM, "Marco Trevisan (Treviño)"
> | <mail at> wrote:
> |> I've just give a try to this [1] kernel image in my Om2008 based
> |> distro... I've read so much about the new LCD touchscreen filters and
> | A few people contributed code/ideas for the touchscreen filtering. I
> | tuned a few things and added a filter.
> For the record, I wrote the bulk of it.

Sure. I should have made that clear.

> Marco is talking only about tap performance I think, and about having to
> use "more pressure", I think what it actually means is "press longer"
> since it is a tap action.  So this will be the discarding action of
> first few samples on tap.  That is also impacting doubleclick then as he
> describes, so I think he actually only has one small issue here with
> early samples after touch detection being discarded.
> Here's an idea for a patch that can improve performance there... at the
> moment, we are able to run the touchscreen ADCs at slowest possible rate
> due to the really good performance of mainly the median filter for
> general tracking.

In mach-gta02 we have:

.presc = 0xff, /* slow as we can go */

We can also have:

.presc_first_points = 0x10,  /* go faster before the first N points
are reported */
.prest_first_points_n = 2;

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