[USRP-users] Exception in uhd_usrp_make (b205mini)

Marcus D. Leech patchvonbraun at gmail.com
Wed Jul 1 16:26:13 EDT 2020


On 07/01/2020 02:03 PM, Nate Young wrote:
> Thank you for the suggestion, unfortunately, the stock image (from 
> /usr/local/share/uhd/images/usrp_b205mini_fpga.bin) had the same error 
> message.
> I also ran uhd_images_downloader to make sure the images were up to 
> date, as well as verified the udev rules were correct.
>
> I started probing the board, and found that the output of the U9 clock 
> buffer chip is not correct.  It is 40MHz, but has a slower speed 
> (~1MHz) on/off modulation to it.
> It turns out the capacitor C90 is no longer on my board ! This 
> capacitor provides stability to the LDO in the CDC3RL02 clock buffer 
> chip, and according to TI, will cause modulation on the output waveform.
>
> So this is likely the cause.  It looks to be an 0402 or 0201 part, so 
> I have ordered some of those in 2.2uF and will see if I am able to 
> replace it.
>
>
One of the issues with teensy SMD parts is that they can be "brushed" 
off a board relatively easily with a mechanical impact that would be
   no problem at all for lower-density through-hole parts.  This is one 
of the reasons I don't like to run these modern boards outside an
   enclosure in a "busy" lab space.





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