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About a touch panel driver of i.MX25 LinuxBSP

Question asked by yuuki on Jan 28, 2015

Dear all,

 

Our system uses touch screen.
RF is used by our system, so noise occurs.

 

For Noise on each pin of touch screen.

   Noise is about 13.3MHz.
   This voltage level is about 700mV.

 

When a noise is given on each pin of the touch panel, we have the problem that the value of the XY coordinate cannot be gotten.

We use a touch screen driver of FSL_LinuxBSP.
(L2.6.31_09.12.00_SDK_SOURCE)

 

We want to know the mechanism of touch screen driver of LinuxBSP.
Would you teach about the following contents?

 

1)
I think that the touch screen driver performs three following measurement.
- X-measurement
- Y-measurement
- Touch screen detection

In the next waveform, would you teach each measuring timing?

touch screen waveform.png

2)
How many times is each item measured?
  - Is it measured once every 1 pulse?
  - Or are several measurement values averaged?

 

3)
Please see next Waveform.
When a noise is added to each pin, it seems to repeat a re-try because measurement is failed.
Is this understanding right?
If so, would you teach the reason that each measurement is failed?

 

touch screen re-try waveform.png

 

 

Best Regards,
Yuuki

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