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  • Case ID: 122531
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Getting deep into capacitive touch driver

Lola

Hi. I am investigating the cap touch for a while, and I am working directly with the capacitive driver from here.

As being said there and other places, the driver will NOT use the COMP, but the ADC to measure, and while I take measurments I have 2 problems :

  1. To measure, as described, there is a resistor(1M) going from digital out to analog in, and the pad sensor goes to analog in. They show in the example that you can connect multiple sensors using this 1 output, but how would you connect 1 digital out, to multiple analog ins? you are going to short all your pads in any configuration you choose ( because pads goes to AINs and the single out goes to ALL inputs after the resistor)

  2. when measuring, they say that when I touch i have to measure higher results , but look what happens when I touch :

:INFO:2 1372  //no touch
:INFO:2 1631 
:INFO:2 1386 
:INFO:2 1798 
:INFO:2 1102 
:INFO:2 1798 
:INFO:2 989   // *touched from here !
:INFO:2 1775 
:INFO:2 669 
:INFO:2 1689 
:INFO:2 667 
:INFO:2 1699 
:INFO:2 759 
:INFO:2 1666 
:INFO:2 717  // still touching

you can see that when i touch there is some sort of square signal and it's not just goes down (or up as it supposed to do ) . I can get over this easily buy it seems wrong.

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    @Bjorn Spockeli thanks, Well I got to say your touch driver costs me too much. I'v spent a very long time trying everything from sophisticated DSP to all sorts of hardware constellations, but you have a serious problem with the ADC. I found out in multiple tests, that the ADC value is NOT STABLE, it doesn't matter what is the configuration, if you put your finger on a pad, the value goes up, say to 1700 stable, and after a few seconds down to 800 stable, then right up to 1700, and back to 800, without me doing anything. This is insane, and it causing me spending too much time because of some bugs with the ADC( in which I could see other people have).

    Don't know what else can I do. it's just doesn't work, values has some kind of periodic error, god knows why.

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    @Bjorn Spockeli thanks, Well I got to say your touch driver costs me too much. I'v spent a very long time trying everything from sophisticated DSP to all sorts of hardware constellations, but you have a serious problem with the ADC. I found out in multiple tests, that the ADC value is NOT STABLE, it doesn't matter what is the configuration, if you put your finger on a pad, the value goes up, say to 1700 stable, and after a few seconds down to 800 stable, then right up to 1700, and back to 800, without me doing anything. This is insane, and it causing me spending too much time because of some bugs with the ADC( in which I could see other people have).

    Don't know what else can I do. it's just doesn't work, values has some kind of periodic error, god knows why.

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