2 Replies Latest reply on Mar 3, 2015 6:14 AM by rahulg_

    Why is auto-calibration should always be used in CapSense designs


      CapSense applications should always have "autocalibration" parameter enabled as this helps in compensating for the PVT (Process, voltage, temperature) variations.




      AutoCalibration calibrates the RawCounts to the required percentage of "resolultion" (the percentage is specified in the respective User Module datasheets). This is done whenever the UserModuleInstance_Start() API is called i.e. on every power up of the device.


      This ensures that the base RawCount value is same across all the devices irrespective of the variations in IDAC, pin/sensor pad parasitic capacitance, temperature etc and hence also ensures the required sensitivity (provided other user module parameters are selected properly as per the tuning procedure mentioned in the design guides/user module datasheets) for all boards.




      If the auto-calibration is not enabled, failures may be seen with some boards due to temperature change/ board to board variations etc.

        • 1. Re: Why is auto-calibration should always be used in CapSense designs



          Your topic is very interesting and helpful !
          I have currently a problem with false detection by temperature rising.
          When I put my system (in operating mode) in the climatic enclosure, at the same time the temperature rise I also mesure the rawcount increase consequently until to switch ON => false detection (around 60°C).


          I remarked also i am not using CSD_plus with autocalibration but only CSD module.
          From the fact I am using a CY8C20347S, I could use autocalibration to solve or reduce the failure.


          My system consist of 3 capacitive sensors used as proximity and each one has different setting (sensitivity).


          But the question, is it possible to enabled autocalibration and control each setting without any changes over time ?
          Does the autocalibration affect only the rawcount dynamically ?


          Thank you by advance.


          Antonin Deschamps.

          • 2. Re: Why is auto-calibration should always be used in CapSense designs

            To solve your problem, you can use either of the two solutions:

            1. Call the UserModuleInstance_Start() API periodically in your firmware. This will ensure that CSD will auto-calibrate according to the new environment by itself.
            3. Select the Sensor Auto-reset feature in the component configuration. This will ensure that the raw count baseline follows the raw counts changing due to temperature variation.