<div class="gmail_quote">On Tue, Jun 8, 2010 at 2:23 PM, John Watlington <span dir="ltr"><<a href="mailto:wad@laptop.org">wad@laptop.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im"><br>
On Jun 8, 2010, at 9:03 AM, Bert Freudenberg wrote:<br>
<br>
> Thanks for inviting discussion!<br>
><br>
> I recently started testing Etoys on the Apple iPad - not the least to get an idea of what needs to be done to it for an XO tablet. Multi-touch is definitely "cool", e.g. you can move around multiple Etoys objects simultaneously. If you are interested, I can send you a test version (pm me).<br>
><br>
> Etoys uses the Sugar tool bar on all platforms. That works very well, the buttons are large enough even for my fingers.<br>
><br>
> However, many other Etoys UI elements are much too small for touching. They're finicky even on the XO screen, but with a pointer you can at least hit them. That's rather hard with a finger (though the Apple touch screen is amazingly precise). A stylus would be preferable, but then, two-finger gestures are awkward with a stylus.<br>
<br>
</div>We aren't planning to provide a stylus (just something for the<br>
kids to loose), but with some touchscreens any pointed stick<br>
can be used as a stylus if needed. The projected<br>
capacitance touchscreens becoming popular (iPhone, iPad), on<br>
the other hand, don't support just any old stylus, it has to have a<br>
special tip.<br>
<div class="im"><br>
> It would help if the tablet had a 4:3 ratio. Ideally 1200x900 pixels just like the XO, but at least preserve the ratio. The iPad has 1024x768 pixels and I made Etoys use a virtual 1200x900 screen hw-scaled to the actual screen size, looks very nice.<br>
<br>
</div>The aspect ratio of a tablet device is the source of much debate<br>
these days. 16:9 displays are cheaper due to volume sales, but<br>
many (most ?) people around OLPC prefer 4:3.<br>
<div class="im"><br></div></blockquote><div><br></div><div>iPad is 4:3, more could follow, so I guess you're referring to PixelQi's current customers?</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im">
>> -----------------<br>
>> 1) Number of simultaneous touches:<br>
>> The number of simultaneous touches that can be tracked.<br>
>> For W7, this is two. I believe OLPC is looking for more.<br>
><br>
> IMHO multi-touch is almost essential on a tablet. Two would be enough IMHO, more are nice.<br>
><br>
> What's "W7"?<br>
<br>
</div>Windows 7<br>
I listed M$'s specifications as most vendors are trying to meet them.<br>
<div class="im"><br>
>> 2) Behavior when number of simultaneous touches is exceeded:<br>
>> If the number of simultaneous touches is exceeded, what happens ?<br>
>> I suggest that the "oldest" touch be forgotten and no longer tracked,<br>
>> but have seen other behaviors as well.<br>
><br>
> I'd rather keep tracking the first touches and ignore additional ones. Then accidental touches wouldn't interrupt the current interaction.<br>
<br>
</div>Interesting point.<br>
<div class="im"><br>
>> 3) Palm rejection:<br>
>> A number of vendors include "palm rejection" algorithms in their<br>
>> controllers. I'm not sure how I feel about this --- I would prefer to<br>
>> push this information higher in the stack before discarding it...<br>
>><br></div></blockquote><div><br></div><div>I would love this on the touchpad of the 1.5 XO also. I keep having problems of jumping cursor when I'm clicking on the pad's buttons.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im">
>> 4) "Sensor size":<br>
>> This applies to multizone resistive touchscreens, which may be<br>
>> thought about as a number of small touchscreens, each capable of<br>
>> a single touch. Two touches cannot be detected in any one zone,<br>
>> so this affects how close buttons which might be pressed simultaneously<br>
>> (think piano keys) can be placed to one another. W7 specs 1 in. x1 in. max.<br>
>> I believe this needs to be closer to 1 cm x 1cm max.<br>
><br>
> I'm imagining to use a two-finger tap to invoke meta operations, like the right touchpad button in Etoys on the XO. For this it would need to detect two kid's fingers form one ...<br>
<br>
</div>Getting closer than 1 cm x 1 cm would probably rule out<br>
multi-zone resistive. But a 1 cm^2 zone would probably work fine<br>
for two finger tap, even with kid's fingers.<br>
<div class="im"><br>
>> 5) Resolution:<br>
>> Do we need to have a touch resolution equal to the screen size ?<br>
><br>
> I have no real experience with this yet, but it needs to be high enough to allow drawing.<br>
<br>
</div>I didn't list W7's specs for this:<br>
2.5mm accuracy for single touches, and 5mm accuracy for multiple touches<br>
<br>
An interesting effect I've noticed is that with some touchscreen, you get smooth<br>
lines when moving your finger at a "normal speed", say 8 cm/s, but when you slow<br>
down (1 cm/s) the line wiggles around.<br>
<div class="im"><br>
>> 6) Scan rate:<br>
>> The number of times a second that the touch controller<br>
>> can identify and report a touch. W7 specifies 50 Hz minimum,<br>
>> which seems a little high.<br>
>><br>
>> 7) Robustness:<br>
>> This is usually specified as the number of presses in one spot with a contact<br>
>> area of either 8mm (finger) or 0.8mm (stylus). Industry standard for resistive<br>
>> (single or multizone) seems to be around 80K, which is too low for our needs<br>
>> (we try to reach a 2000 day lifetime). But the one vendor supporting 250K<br>
>> touches was unusable by a bare finger (needed fingernail or stylus).<br>
>><br></div></blockquote><div><br></div><div>Not that the 250K touchscreen probably needs it... but will the other one be replaceable, if necessary?</div><div> </div><div>Best regards,</div><div>Tiago</div><div><br>
</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="im">
>> 8) UV resistance:<br>
>> Since this touchscreen is on top of a sunlight readable display, it will need<br>
>> to be UV resistant. Our current standard (for the display) is no significant<br>
>> change (>5%) in optical properties after 4000 hours of full sunlight UV<br>
>> irradiation.<br>
>><br>
>> 9) Humidity, temperature:<br>
>> Same as the XO: operation from 0 to 50C, in RH up to 95%.<br>
>><br>
>> Regards,<br>
>> wad<br>
><br>
> No opinion on these issues, yet ...<br>
<br>
</div>Keep experimenting!<br>
<br>
Thanks,<br>
wad<br>
<div><div></div><div class="h5"><br>
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