5 Replies Latest reply on Apr 15, 2019 10:24 PM by user_236195066

    PSoC5LP Finger threshold and noise level for CapSense tuning

    user_236195066

      Hi,

       

      We are currently doing CapSense tuning for PSoC 5 LP.

      The following phenomenon occurred while tuning.

       

       

      Tuning.png

       

      The above screen is in the initial state.
      A high noise level is displayed.

       

      Just changing the finger threshold(FT) from 190 to 180 lowers the noise level as shown in the screen below.

       

      We can't understand that the noise level changes just by changing the finger threshold(FT).

       

      This phenomenon happens occasionally but do you understand why?
      Or is there any way to deal with it?

       

      Regards,

        • 1. Re: PSoC5LP Finger threshold and noise level for CapSense tuning
          ShanmathiN_06

          Hi,

           

          This issue seems strange. Ideally, changing the finger threshold should not cause any change in raw counts.

           

          Could you pls check the following and post the updates?

          Can you read the raw count value using Bridge control panel or print the raw count value in UART? This test is to ensure that Tuner I2C host is reading the correct raw counts value.

           

          Also, is there any scenario when this phenomenon is observed? Maybe, I can try at my end with the same configuration (Pls send yours) and see if I could reproduce the issue.

           

          I see from the images that SNR is lesser even though noise level is low. Could you pls confirm this? Is the signal also lesser when noise is lesser?

           

          Thanks,
          Shanmathi

          • 2. Re: PSoC5LP Finger threshold and noise level for CapSense tuning
            ShanmathiN_06

            Hi,

             

            Were you able to resolve your issue? Pls post your updates.

             

            Thanks,

            Shanmathi

            • 3. Re: PSoC5LP Finger threshold and noise level for CapSense tuning
              user_236195066

              Shanmathi-san,

               

              Sorry for the late reply.


              We have debugged the board.

              Raw count was output correctly.

               

              The cause of the problem is:

              1. Power on the board of PSoC5LP.

              2. Turn on LED for CapSense.

              The LED lighting at this time appears as noise.

              3. Changing the finger threshold updates the baseline and reduces the noise level.

               

              Therefore, I thought that setting the noise threshold high would solve the problem, but a new problem occurred.

              A phenomenon occurs in which the baseline does not follow even below the noise threshold.

               

              Do you know why the baseline does not track noise?

               

              Regards,

              Masashi

              • 4. Re: PSoC5LP Finger threshold and noise level for CapSense tuning
                ShanmathiN_06

                Hello Masashi-san,

                 

                Have you enabled "sensor auto reset" option (CapSense CSD component configurator window -> Advanced tab)?

                 

                If you have enabled auto reset option, then baseline is always updated independent of the noise threshold. If not, then baseline will be updated whenever difference counts/ signal is lesser than noise threshold.

                 

                Pls send your raw count wave forms, when you face the baseline update issue, along with your CapSense configuration.

                 

                Thanks,
                Shanmathi

                • 5. Re: PSoC5LP Finger threshold and noise level for CapSense tuning
                  user_236195066

                  Shanmathi-san,

                   

                  Each channel was found to follow or not follow the baseline.

                  It was also found that all channels follow the baseline when set to auto.

                   

                  Does the baseline fail to track due to parameter settings?

                  For example, IDAC value is low, Analog Switch Divider value is low, etc.

                   

                  We will send you a CapSense configuration file for reference.

                   

                  However, the operation may differ depending on the surrounding environment,

                  so your company may not be able to reproduce it.

                   

                  Regards,

                  Masashi