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[Desay SV] TSC2007 has spike at X/Y and I2C read back additional error values

Rocson He
Intellectual 1830 points
Other Parts Discussed in Thread: TSC2007

Hi Team,

We now get one question from automotive customer Desay SV using TSC2007, there some spike at the X/Y driver, thus leading to error interrupt and error I2C returned values. So when writing, it’s apt to have long lines written.

Please see more details are as attachment waveforms, and schematic. (Too large, and I have sent to Andy in Email)

Could you help check if any comments and how to improve it ?

Thanks.

 

  • 0
    TI__Guru 52115 points

    Hi Rocson,

    I will take a look today and get back to you soon.

    Andy

  • 0
    TI__Guru 52115 points
    Hi Rocson,

    It might be an EMI noise. I see in their schematic four decoupling capacitors (220pf) are on the 4 analog inputs pins. I suggest they try to put 4 0.01uF caps instead to see whether there is any difference.

    Andy
  • 0 in reply to Andy Liu (BMS)
    TI__Intellectual 1830 points

    Andy,

    Thanks for your suggestion. I have talked with custoemr to try the test, they will feedback tomorrow.

    Also, as the spike happen at X+, X- level back to high level, could TSC2007 still sense the spike thus lead to the error additional line? Do you think any other suspect points when comparing with normal behavior ?

    Thanks.

  • 0 in reply to Rocson He
    TI__Guru 52115 points
    Hi Rocson,

    Basically the TSC2007 is a purely salve device. It does all the things that the host microcontroller tell it to do. If it is still sensing the spike, it simply means that the TSC2007 has got the some commands from the host. It will be good to ask the Desay firmware / software engineer to take a close look at the code which handles the last coordinates from the TSC2007 right before the touch is off.

    Andy
  • 0 in reply to Andy Liu (BMS)
    TI__Guru 52115 points
    Hi Rocson,

    Another issue you may want to double check with Desay is that in their firmware or Windows / Linux driver they use the /PENIRQ pin to determine whether the touch is still present. When /PENIRQ pin is low, it means that the touch is still on. Otherwise, the touch is just gone.

    Andy