[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
> 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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