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TSC2046E: How does /PENIRQ work and how does it detect when a finger is released?

Part Number: TSC2046E
Other Parts Discussed in Thread: TSC2046,


Is my understanding correct?

1. When the touch panel is touched, /PENIRQ goes "LOW", and when SPI communication is started, it goes "HIGH".

2. After sending PD0=0 by the control command, the pen touch function is enabled again when the AD conversion is completed, so if the touch screen is still touched, /PENIRQ will immediately go "LOW" again.

I think the /PENIRQ signal does not change when the finger is removed from the touch panel.

I would like to know if there is a recommended method for detecting when a finger is removed.

Best Regards

  • Hi Kazunari,

    Can you share a screen capture showing your SPI communication lines and the BUSY signal?  Perhaps a schematic of your TSC2046 circuit as well?  Both points above seem correct, but I don't understand why you think there is no interaction when the finger 'touch' is removed.

  • Thank you for your quick reply.

    Since we are currently in the process of investigating whether to adopt TSC2046E before designing, we do not have a schematic or actual waveform images, but we have created a chart of what we are assuming.

    Initially, we assumed that the falling edge of PENIRQ would be used to interrupt the host side. With your answer, I now understand that I can generate an interrupt even when the touch is removed by using the method of generating an IRQ for the host with level monitoring.

    Is this understanding correct?

    We are assuming that the IRQ for the host is masked during communication.
    The timing in this chart is very short, so I know it is rare.
    After this, if there is no touch, the PENIRQ will not change.
    So I understood that we need to generate the IRQ we want after unmasking by comparing the difference with the state of the PENIRQ before masking.

  • Hi Kazunari,

    It is recommended to disable the PENIRQ function after the initial touch is detected (PENIRQ goes low), and the TSC2046 disables the function during X,Y measurements which will help in the avoidance of multiple interrupts being registered by the host.

  • Hi Tom san,

    Thanks for the answer.

    I understand about disabling /PENIRQ after the first touch is detected.
    I have one more question.

    Please tell me about the signal when /PENIRQ is disabled.
    I think we can disable /PENIRQ with the bit of PD0 that sends the command, but when it is disabled, will the output of /PENIRQ be L or H?

    L: The red dotted line in the figure. It keeps the same state as when it is disabled.
    H: The red solid line in the figure. When it is disabled, /PENIRQ is disabled.

    Best Regards.

  • Hi Kaunari,

    If you set PD0 to 1, the PENIRQ is disabled and will be high due to the internal pull-up.  The device will not respond directly to 'touch' so long as there are no conversions taking place.  If you read through the third paragraph below Figure 10 though, you will see that during the X, Y and Z measurements, the PENIRQ is disabled and low - so you will see it toggle low through the measurement phase even if its disabled.

  • Hi Tom san,

    Thank you for answering so many times.

    I now have a deeper understanding of the specifications of this component.

    We will check the parts by using them in prototypes.

    Thank you very much.

    Best Regards.