Sensitivity/reaction time of 7" touch display

NETMF & Gadgeteer
1

I have a FEZ Cobra + 7" touch display, but I’m not so satisfied about the sensitivity/reaction time of the FEZ/display. Sometimes the response is very slow, making me think I have to push the display harder.

I can think of two reasons:
[ol]
The sensitivity of the display is not so good - anyone knows a way to control this?
FEZ reacts too slow, which seems odd, as FEZ is not doing anything besides showing the display and waiting for one button (of three) to be pressed.
[/ol]

Any suggestions?

2

Are using WPF? If so then this is why things are slow.

Also, this is a resistive touch and works by force. You can use capacitive touch instead and it will be very sensitive

3

Thanks for your reply Gus.

I’m afraid I have some stupid questions about this item. Please don’t shoot me for asking them :).

  1. How to tell whether or not WPF is used? I took a MS sample and modified that.
  2. How to avoid using WPF? Are there any samples available?
  3. Using capacitive touch would mean another display instead of the 7" display. Is that right?
4

Take a look at this http://wiki.tinyclr.com/index.php?title=GHI_Graphical_Demo and maybe try on your board. Things run very fast, even a little video game runs fine.

Also, take a look at Pyxis 2 please http://www.skewworks.com/
It is an OS running on top of NETMF

When you are not using WPF, which you are since you use the Microsoft examples, you will be using Bitmap class to draw directly on the screen.

GHI is already implementing libraries to help out in this area so stay tuned for near future announcements.

5

JdV,

  1. If you’re using the MS sample you’re using WPF. The second you load the TinyCore reference you’re going to lose performance; whether you use it or not.

  2. I have a sample for gathering touch information sans WPF in Code.TinyClr.com. The GHI sample also works w/o WPF as does Pyxis 2. (pyxis2.codeplex.com)

  3. Yes that would mean a different screen or replacing the existing touch screen on top of the LCD w/ a capacitive one.

6

Hi guys,

My customer stil isn’t satisfied with the sensitivity of the display yet.

Today it seemed to make a difference if the customer takes off his shoes.
Shoes on => bad sensitivity of the display
Shoes off => much better sensitivity of the display

This makes me think there might be some influence of a kind of static electricity. Is that possible?
Does it make any sense to ground the display? In what way should that be done?

TIA

7

Wow!
I see a business opportunity - “FEZ certified shoes”! ;D

8

Resistive touch screens depend on pressure, so taking off your shoes probably just smells bad. Some 7" touch panels have somewhat lousy precision, depending on whether you are using 10-bit or 12-bit resolution ADC - but the response should not suffer. Unless the your software is ignoring values that don’t change. Is he using a stylus or his finger (/ toe)?
Write a small routine to just read the position of the stylus and see if there is a problem with the required sensitivity over the surface. Maybe the touch layer is defective?

FEZ shoes? Might be an interesting side business.