4 Replies Latest reply on Jul 18, 2019 12:04 AM by SuKa_4300241

    Proximity sensing Rawcount



      I made a repeatability test on cypress CY8CKIT-040 KIT with cap-sense version 6.0.

      In repeatability test what i found is the raw-count vary from one test to other test when there is nothing to sense at fixed ambient conditions and i have a PCB with copper trace connected to the cypress.

      Can please help me with why the raw count vary for same test when we repeat it?

      Does parameters I fixed in cypress make this happen?

      I expected to have same raw count at beginning when there is nothing to sense if i repeat test.


      I have attached a word file that it would be clear about my question.

        • 1. Re: Proximity sensing Rawcount

          Hi SuKa_4300241


          A variation in raw counts is expected due to noise in the environment. This is the normal operation and this shift in raw counts is common. These variations could be due to temperature differences, difference in humidity, moisture level, etc.


          Could you please let us know if you are using a wireloop proximity sensor or the Cypress proximity sensing shield?


          Thanks and regards


          • 2. Re: Proximity sensing Rawcount


            I am using button sensor design by us.not the loop sensor.

            The variations cant be because of temperature effect r environmental conditions because in my case because i am using ambient environmental conditions using a setup.

            Is there any other technical reason that i get raw count difference?

            Can you give any suggestions like sensor design or other tings to get simultaneous raw count for reputability tests?

            • 3. Re: Proximity sensing Rawcount

              I'm assuming you are testing repeatability amongst different power up/reset sequences, if so, the variation may also be because of auto-calibration algorithm which re-calibrates IDAC every boot. A +/-1 IDAC code difference can be expected depending if you have a borderline Cp for example. Can you try disabling auto-calibration and test?


              Also, what is the rawcount change your are noticing? Can you elaborate on your setup, CapSense configuration and test procedure. Note that even in ambient conditions, rawcount may change if you have tuned the sensor to be very sensitive. The change could also be due to power supply variations.

              Since the rawcount changes, CapSense component doesn't rely on absolute value of rawcount to detect touch/proximity etc. It looks for a specific change pattern in rawcount at run time to detect such events.

              • 4. Re: Proximity sensing Rawcount


                we are not using the IDAC auto-calibration but a fixed IDACs, both set using the Tuner program. we are sure that the environmental conditions are stable during the time (inside a climatic chamber with fixed temperature and air humidity), that we are transferring the data to a PC using a Bluetooth module and we are giving the power supply using a battery pack connected to the mini-usb port. The variations are big compared to a touch on the PCB so the sensitivity is not extremely high. Do you have other suggestions or possible reasons for that behaviour.