[Olpc-open] jumpy cursor problem and sugar issue

[Sameer Verma]

Steve Holton wrote:
> Do you have a way to accurately measure relative humidity?
>
> I saw pretty severe trackpad issues on one of my XO's on a single day 
> and haven't seen a re-occurrence yet.
> At the time, it looked clearly related to static fields.
>
> On the other hand, I have seen (and fixed) a very similar behavior on 
> a NintendoDS touchpad which was caused by dust or sand becoming 
> trapped under the frame along one edge.
>
>
> Just a theory (I have no data to indicate this works) but when you see 
> the touchpad problem on an XO could you try this and report back with 
> success/failure/experiences:
>
> On an XO showing jumpy trackpad problems:
>
>    1. Raise the screen to full vertical / perpendicular.
>    2. Rotate the screen 1/8 turn clockwise (reverse this for left-handers)
>    3. With the right hand palm facing up, reach under the screen and
>       put a finger on the metal mounting bracket or screw of the
>       swivel hinge.
>    4. With the finger still in contact with that (essentially a
>       chassis ground), lightly brush the trackpad with a finger of the
>       other hand to drain stray static charges into the chassis.
>    5. Re-calibrate afterwards, if necessary.
>
>
> If you have an available earth ground, discharging to that as well 
> might make an interesting variation on the test.
>  
>

Most that touchpad issues arise from two distinct sources: driver and 
capacitance grounding. In touchpads, the finger acts as a virtual 
grounding device. Dust/dirt/grime may create problems with this 
grounding effect. So, cleaning the pad and grounding any extra static 
buildup (Steve's solution above) should help. I don't know much about 
touchpad driver issue(s) if any with the XO.

See http://en.wikipedia.org/wiki/Touchpad#Theory_of_operation
http://www.synaptics.com/technology/cps.cfm
http://www.synaptics.com/products/touchpad_faq.cfm#Q2

Sameer
>
>
>
>
> On Sun, Apr 27, 2008 at 7:50 AM, Bryan Berry <bryan.berry at gmail.com 
> <mailto:bryan.berry at gmail.com>> wrote:
>
>     Day 3 of the pilots at Bishwamitra and Bashuki and couple of
>     issues have
>     come up
>
>     1. We are having a lot of trouble w/ jumpy cursors. You know where the
>     touchpad behaves erratically. Is there an easy fix to this problem?
>
>     we are using build 703, MP machines, and firmware Q2d14. We have the
>     kids hold down the 4 corner buttons as recommended in the XO user
>     guide
>     but that doesn't seem to consistently fix the problem.
>
>     Dust is an issue at the schools but that can't explain the high
>     rate of
>     jumpy cursors. Please assist
>
>     Suggestions?
>
>     2. For future reference: In general the kids and teachers find it
>     quite
>     confusing when they move the cursor to the corners of the screen
>     and the
>     Sugar frame pops up. The kids have learned the top row keys very
>     quickly
>     - faster than I thought - and they find the frame popping up quite
>     confusing. They have learned to use the frame button already.
>
>     pictures to come and a full write-up, I promise!
>
>     Bryan W. Berry
>     Systems Engineer
>     OLE Nepal, http://www.olenepal.org
>
>
>
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>
>
>
>
> -- 
> Steve Holton
> sph0lt0n at gmail.com <mailto:sph0lt0n at gmail.com>
> ------------------------------------------------------------------------
>
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