2 Replies Latest reply on Jul 18, 2016 2:01 AM by userc_39894

    CapSense - Slider - Resolutions - Centroid Update Rate



      I started a month ago with CapSense on PSoC1 and I'm still a bit confused about some resolution meanings.


      Technical background: CY8C21534 - PSoC Designer 5.4 - CSD Version 2.0 - and a slider made of 12 sensors.

      •  Resolution as the one set in the Parameters - CSD Window of the PSoC Designer

        (Print screen from my project)

        Are we talking about the one of each individual sensor (low level), i.e. for each part of the slider?

      • Resolution as the one set in the CSD wizard

        (Print screen from my project)

        Is this the [computed] resolution of the whole slider?
        Could it be that that centroid's maximum value in the high level API is this resolution minus 1?
        It says Sensor Resolution in the little hint window, that confuses me and the both next points confuse even more
      • Max resolution as said in the datasheet of the CSD module

        (Picture below comes from the CapSense® Sigma-Delta Datasheet CSD V 2.00

        According the formula, max value = ( Pins - 1 )* 2^8 - 1 so why does the hint say range is up to 65535 when having 8 Sensors Count?
        Thought this will be 7*256-1 = 1791

      • Finally, even more confusing (see picture of my CSD wizard), why is the Resolution set to 4095 in my design when having 12 Sensors for my slider? max value = ( Pins - 1 )* 2^8 - 1 = 11*256-1 = 2815

      • Last question, I've to find out the centroid's update rate.

        I guess it's the scanning speed of each sensor times number of sensors (12 in my case) plus some computing time, am I right?
        Is the scanning speed I have to take the one told in the Table Scaning Speed and Resolution from the CapSense Design Guide of my PSoC part?
        Any knowledge about execution time of the API or do I have to calc/measure by myself? Couldn't find anything in the documentation until now.

      I was set on an existing project that has been discarded few years ago and there is nobody around from that time to clarify.


      Thanks a lot for help


      Kind regards

        • 1. Re: CapSense - Slider - Resolutions - Centroid Update Rate

          I've to apologize, pics seem to have disappeared in original post.
          I'm attaching them in this post





          • 2. Re: CapSense - Slider - Resolutions - Centroid Update Rate

            Hello again


            I spent again a few hours on PDF reading and did some tweaks on the CY3214 Demo board with the example project, as well as the prototype I was given and I'm pretty sure I've some answers.

            • Resolution as the one set in the CSD wizard (for the slider)

              This must be the computed resolution of the slider and its max value is given by (number of sensors - 1) * 2^8 - 1.
              And the centroid max value is this resolution minus 1. Plus, centroid with 0xFFFF does mean no finger or error.

              BUT!!!!! CSD wizard accepts resolution values beyond  the maximum without complaining (at least CSD version 1.5) but this is probably a mistake (= BUG).
              CSD version 2.0 does correct automatically when entering anything above that max value to the max value according the formula.

              Moreover, when importing an old project to the actual PSoC Designer an module version (Designer 5.4 and CSD 2.0) it does not detect the mistakes made in the old version.

              The hint that says resolution has to be between 5 and 65535 is - I guess - an absolute range as the API works with WORD size.