3 Replies Latest reply on May 10, 2011 5:52 AM by content.librarian

    Switching between proximity and touch sensing for a 3x4 keypad

    michael.beaster

      I'm working on a 3x4 button keypad using a CY8C21434. I'd like to be able to detect proximity and also be able to read the status of the buttons. When proximity is detected, the LEDs behind each key illuminate to present the user with the keypad. The implementation suggested to me by the FAE is the following:

         

       

         

      1) Gang together 4, 8, or 12 sensors in normal operating mode using the analog mux, creating a lot more copper surface that will be more sensitive for prox detection. Once proximity is detected, the part can go into a different operating mode, wherein each key is independent

         

      2) Since the large prox detector sensor will have much higher capacitance, 2 different bleed resistors are required on different pins, connected through the global out bus.

         

       

         

      I'm just a little confused about how connected multiple sensors to the mux actually connects them together. It was suggested that I set/unset the right bits in MUX_CR0, MUX_CR1, MUX_CR2, and MUX_CR3. But I'm still a bit foggy on how this connects the sensors together etc. Has anyone worked on an implementation like this? I could use a code sample or a few pointers on how to proceed. Thanks.