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Original question:

CC2531: Using an external 32MHz oscillator, do I need to do anything with the XOSC_Q2 pin?

CC2531: Failed USB enumeration / no clocking

Charles Ryland
Prodigy 60 points
Part Number: CC2531

Tool/software:

Since I never heard back about using an external oscillator, I have switched back to using a 32MHz crystal tied to pins 22 & 23 with loading caps.  When powered, the chip always enumerates with my laptop (windows) regardless of being held in reset or not.  The enumeration is "unknown USB device: device descriptor request failed."  I am unable to connect to the CC2531 via the cc debugger, so the the chip should have no code loaded into it (factory fresh).  When I probe onto my crystal lines, there is no clock signal, which I suspect is the problem.  Any advice on what might be causing this?

Thanks.

  • 0
    TI__Expert 5810 points

    Hi Charles,

    Generally speaking trying to probe the clock lines directly may not work as you load the line with your scope probe you end up disrupting the crystal circuit. In any case on startup with no software loaded the crystal shouldn't be in use anyways. On reset the 16MHz RCOSC would be running and I believe that you'd have to switch to 32MHz XTAL via software:

    I would start looking at other parts of your circuit for root cause for not being able to connect with the CC Debugger. 

    BR,

    Jake