2 Replies Latest reply on Sep 13, 2012 12:25 AM by gaya

    FX2LP fails to enumerate

    chris.mcclelland

      I have three identical FX2LP boards, one of which works fine, the other two fail to enumerate. Has anyone got any hints for things I can try (hardware and/or software) to discover what's up?

         

      The working board enumerates like this: http://pastebin.com/raw.php?i=RApTG5E8

         

      The non-working boards are detected as high-speed devices: http://pastebin.com/ND0HQuW9

         

      ...but fail to respond to the host's descriptor requests: http://pastebin.com/raw.php?i=gy2EY0nh

         

      The hardware is pretty minimal:

         

      1) 56-pin SSOP CY68013A (1st bad board) and CY68014A (2nd bad board)

         

      2) D+, D- & GND connected to USB

         

      3) Reset circuit: 22nF capacitor charged through 100K resistor

         

      4) Clock circuit: 24MHz crystal and a pair of 22pF capacitros

         

      5) Two 22nF decoupling capacitors

         

      6) External 3.3V PSU

         

      7) Everything else unconnected (for now)

        • 1. Re: FX2LP fails to enumerate
          chris.mcclelland

          Never mind, I fixed it.

             

           

             

          I noticed a design fault in my schematic - the SDA line has a removable link to allow the FX2 to be isolated from its EEPROM. Unfortunately, the pull-up on the SDA line is on the EEPROM side, not on the FX2 side as it should be. So the SDA line on the FX2 was floating. I soldered in the link and all is well. I guess since SDA was left floating the startup behaviour is undefined; it just happened to work on one board and not on the others.

          • 2. Re: FX2LP fails to enumerate
            gaya

             Hi,

               

             

               

            Thank you for posting the fix. It might be useful for others with similar issues.

               

             

               

            Regards,

               

            Gayathri