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gen4-4D-CAPE-43CT pinout

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  • gen4-4D-CAPE-43CT pinout


    i have been looking at the gen4-4D-CAPE-43CT datasheet. From the schematic it look like the display uses I2C1 and I2C2 buses of the beaglebone. There is not info in the datasheet to figure
    out why. Is there a system block diagram that shows how it is connected to the beaglebone black/green or what pins are actually used and for what?

    If there is system reference manual you can point me to that would be nice.

    thanks for your help.

  • #2
    Please refer to the gen4-4DCAPE Adaptor schematic on page 10 of the datasheet, that then shows you the connections to the BBB, as the gen4-4DCAPE-43CT doesnt directly connect to the BBB itself.

    It uses both I2C bus's, as one is dedicated to EEPROM, and the other is used for the Touch Panel. Other devices can still use the I2C, as its a shared bus, you just cant use the same address as the touch panel obviously.

    I hope that helps


    • #3
      thanks for your response James

      Not that I needed to use the buses, I was actually comparing with the CAPE-70T datasheet - only uses one pair of I2C, you also a diagram that shows a little more clearly how the P8 and P9 headers connect to the beaglebone.

      One more question, just out of curiosity, why would you even need the EEPROM in the first place since everything is done on the beaglebone?


      • #4
        Hi again,

        Yes the old 4DCAPE's had their resistive touch operating through the Analog pins on the Beaglebone Black. This had varied results, as the software which controlled it was built into the kernel, and depending on many factors it might work OK sometimes and not other times, and we had reports of false touches or self touches, which we had no ability to control as we dont control the software.

        So with the gen4-4DCAPE's, we added an I2C touch controller for the resistive touch models, or an I2C capacitive touch controller for the capacitive touch panels. This not only freed up the Analog pins on the BBB for the User, but also means we dont have to deal with noisy touch anymore.

        I have put in a request to get a diagram added into the gen4-4DCAPE datasheet, to better show the pin usage. Thanks.

        The EEPROM is part of the CAPE standard, it tells the BBB what CAPE is attached to it, so it can load the correct overlays and the correct drivers to operate that Cape.



        • #5
          thanks so much. this clears things up quite a bit.


          • #6
            hi again

            Am I right when I assume the TOUCH_IRQ (pin 26 of P1_B - pg 10 gen4 datasheet) is just a random GPIO pick as an interrupt source for the gen4 LCD and has nothing to do with the touch screen controller of the AM335x itself?


            • strancara
              strancara commented
              Editing a comment
              Hi, you are right, TOUCH_IRQ has nothing to do with internal AM335x touch controller; it can be any GPIO. On gen4, touch controller is an external I2C device which requires I2C pins (SDA, SCL) and an additional GPIO for triggering interrupts.

          • #7
            hi again

            any reason i'm not getting an answer to this question? James? anybody? please. I need to be able use this display on another board thats why i'm asking.

            The way its labelled makes it seem special but it looks like its just a random GPIO used as an interrupt source. Is this correct?


            • #8
              Hello again,

              Sorry I don't normally man the forum, and I didn't see your response to me.

              TOUCH_IRQ is just a GPIO which the driver looks for. Its all specific to the drivers loaded for the gen4-4DCAPE's.

              I will get our software developer to reply to you, so you have more information.



              • #9
                thanks so much.