2 Replies Latest reply on Sep 13, 2012 12:25 AM by GayathriV_16

    FX2LP fails to enumerate

      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

          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





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