6 Replies Latest reply on Jul 14, 2020 11:06 AM by buckd

    UZEV USB as host and custom carrier card, problem with USB_OTG_CPEN held low

    buckd

      Hi,

       

      We are designing a custom carrier card for the UZEV and we have a problem with the USB interface with the USB_OTG_CPEN pin always held low. We want to use it as a host and we have the following setup:

       

      1. Copied the hardware design from the Carrier Card in the starter kit and have this set-up

         * JP21: pins 1-2

         * JP12: ON

         * JP22: pins 2-3 (accidentally grounded our our board, see below)

         * JP23: pins 1-2

      2. Our only change was to ground pin2 of JP22 (a mistake, see below)

         * To see if it mattered, we grounded pin 2 on the UZEV-CC, power cycled, and it still worked fine as a USB host.

      3. Our Linux/bitstream boot from an SD card and works on both the UZEV-CC and our custom carrier card. It loads USB on the UZEV-CC which suggested to us a hardware problem.

       

      In probing every aspect of the circuit we learned that USB_OTG_CPEN was always low. I put a 1.8K pullup on it to 3.3V to see if it would change, but it is actively held low.

       

      What would cause USB_OTG_CPEN to be held low like this?