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USB Low-Full-High Speed Peripherals

Anonymous
Not applicable

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)

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Anonymous
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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.

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Anonymous
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 Hi,

   

 

   

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

   

 

   

Regards,

   

Gayathri

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