1 Reply Latest reply on Jun 18, 2019 1:19 AM by XiaoweiZ_71

    Palm holding the touchpad question

    DeXi_1316761

      Hi, All,

           I meet one question. After the palm was holding the touchpad(7*7) for the long time, the palm leave from the touchpad, the raw data will fall quickly at once,  but it higher than the baseline yet. After this, the raw data will slow down. The raw data need a long time to fall to the baseline. Pic1.jpg

           you can repeat this problem on CY8CKIT-041-40XX KIT, and use the CE211584 project. You need cancel the following code.

                //if(sensorCout > ACTIVE_SENSORS_PALM)

                //{

                //    ...

                //}

           I think, the reason is the temperature change. How about this? How to handle it?

           Note: The palm hold the touchpad for a long time(10 minutes). In this period,  you maybe move your palm in a small range, and did not leave the touchpad. The raw data will change in this case yet.

        • 1. Re: Palm holding the touchpad question
          XiaoweiZ_71

          This is typical temperature drift issue.  FPC is very thin, the heat of the palm is easy to raise its temperature, cause intrinsic cp of each sensor increase. When palm removed, the temperature of FPC cannot decrease to original status suddenly, so the rawdata also cannot fall down suddenly.

           

          This phenomenon is not that easy to reproduce on PCB board because it's thick and raise its temperature is not easy.