11 Replies Latest reply on Oct 29, 2012 3:05 PM by user_101879199

    Using CapSense to sense something other than a finger

    user_101879199

      I found a forum post that indicates one can increase the sensitivity of CapSense to detect a finger inside a glove.

         

      How would a developer detect (for example) a felt pad or a voltage biased metal probe moved into "contact" with a CapSense button or slider?  What approach would you take to experiment with this concept using the -001 DVK?

         

      Thanks and regards

         

      Tim Miner

        • 1. Re: Using CapSense to sense something other than a finger
          user_1377889

          There is the possibility of using a "Tuner" for the buttons and you can monitor the changes of the readings to get a feeling if the changes are sufficent for a safe button detection. Have a look into the datasheet for the CapSense CSD and search for "Tuner".

             

           

             

          Bob

          • 2. Re: Using CapSense to sense something other than a finger
            user_101879199

            Thank you. Will work on that some today. regards Tim

            • 3. Re: Using CapSense to sense something other than a finger
              user_14586677

              "voltage biased metal probe moved into "contact" with a CapSense button or slider?"

                 

               

                 

              First instinct when I read this is if biased probe shares a common ground, and it exhibits, relative

                 

              to PSOC leakage of a pin configed as HiZ, looks like a v source, simply detect it as a logic

                 

              level present or absent. May have to be scaled, or offset, but simple interface is all it needs.

                 

              If Vprobe has a wide range use A/D to establish threshold. Or a comparator.

                 

               

                 

              If ground is not shared, then treatment as an isolated ground, you have to examine common mode

                 

              problem, which also can be handled if not a crazy CM enviroment, like KV........but there are easy

                 

              approaches to this as well.

                 

               

                 

              Of course you have additional considerations, noise, drift, offsets, but those are pretty much standard

                 

              analog issues.

                 

               

                 

              How accurate is the bias, what is its Z, drift, noise......?

                 

               

                 

              Regards, Dana.

              • 4. Re: Using CapSense to sense something other than a finger
                user_101879199

                Hi Dana,

                   

                Your reply on this one is pretty dense... as in I don't understand it all. It does give me hope though.

                   

                I just got my -030 board working and do not yet have a -031 Kit. For some reason, I thought the -030 board had the I2C connections for the EzI2C CapSense Tuner on board... if it did, I would be experimenting already with the CapSense slider and buttons on the -030 board.

                   

                I want to embed a slider into/onto a plastic piece and detect the position of a pseudo finger on another plastic part that is snuggled up with the first. I don't want them scraping each other, I just want one detecting the other. The pseudo finger is the felt pad or biased probe I refered to. No high voltages or anything. Think of it as a non-Human Interface Device... haha.

                   

                A related question is: Do you know if anyone has used an inner PCB layer for the Capsense buttons and sliders and the board material as the overlay?

                • 5. Re: Using CapSense to sense something other than a finger
                  user_14586677

                  This does sound like a capactitive or optical approach in which the finger becomes a sliding shutter.

                     

                   

                     

                  In so far as inner layers used in C sense, I have never seen any posts or ap notes discussing that.

                     

                   

                     

                  Regards, Dana.

                  • 6. Re: Using CapSense to sense something other than a finger
                    user_1377889

                    I'm afraid you'll need a miniprog 3 to use the CapSense tuner on a -030 board, although I didn't try that yet. The I²C is not connected through the Fx2 - bridge.

                       

                     

                       

                    Bob

                    • 7. Re: Using CapSense to sense something other than a finger
                      user_101879199

                      Hi Dana,

                         

                      I have a mini prog3 and a -001 board as well. Can I use the Tuner with that stuff?

                         

                      What I saw on a -031 video was (using the -001 board with -031 kit) the miniprog3 in the tuner mode and plugged into a header on the -031 adaptor board. So, I still have to wait for the -031 kit right?  OR is there a tuner connection on the -001 board?  I will start looking but I think I misunderstand and got too excited.

                         

                      I've got to sit down and try to understand the CapSense CSD component datasheet now.

                         

                      Tim

                      • 8. Re: Using CapSense to sense something other than a finger
                        user_14586677

                        The Miniprog 3 has a dual function, a programmer/debugger and an I2C

                           

                        bridge for the tuner and other. I looked at schematic of Miniprog 3 and it

                           

                        does not bring out I2C to 10 pin (on processor module), and there is no

                           

                        5 pin on main board (Miniprog does bring out I2C to its 5 pin). So I think

                           

                        you need the additional adapter boards.

                           

                         

                           

                        That being said, might be possible to cobble the Miniprog 5 pin connector via proto block

                           

                        and get it hooked up to function, I have not had the time to confirm if that can be

                           

                        done, take a look at schematics of P Module and -001 to see if you can accomplish

                           

                        that.

                           

                         

                           

                        Regards, Dana.

                        • 9. Re: Using CapSense to sense something other than a finger
                          user_1377889

                          Here is a thread where a community member has solved that problem. Mybe you'll get yours right when you follow the hints...

                             

                           

                             

                          Bob

                          • 10. Re: Using CapSense to sense something other than a finger
                            user_14586677

                            This ap note covers the -001 and using the tuner, attached.

                               

                             

                               

                            Regards, Dana.

                            • 11. Re: Using CapSense to sense something other than a finger
                              user_101879199

                              Dana and Bob,

                                 

                              Thanks you both for the help.

                                 

                              Bob, I do not see the link to the thread yet. But it sure sounds helpful.

                                 

                              Dana, Your link is similar to the section in the CSD component data sheet starting on page 28 "Tuner GUI User Guide. I am sure I will be using them both.

                                 

                              So, just to clarify... the Tuner GUI is something the Creator IDE launches. It gets the data about my designs CSD component via a I2C slave component (EzI2C) that I include in my design. I also have to physically connect 2 pins from that I2C slave to

                                 

                              the SDA(T) and SCL(K) pins on the miniprog3 dongle. That dongle uses its USB ( and an on-board I2C master) connection to the PC to provide the Tuner GUI with 'streaming' data that it then displays and uses to Tune my design (Auto) or give me access to results (constants) that I can include in my design myself (Manual).

                                 

                              Yes?

                                 

                              I do think I saw something in the CSD component data sheet where if you enable tuning, it instantiates the EzI2C component for you and then tells you to go into it to set a parameter. BUT my head is still trying to wrap around the convolutions.

                                 

                              I will try to get unconfused soon. Anyway, thanks again for all the help.

                                 

                              Tim