Debugging a limited failure LimeSDR USB

Projects LimeSDR
1

I picked up a second LimeSDR USB board and I installed it into a nice case, and was running through the basics and its acting a bit strangely. Specifically, on the selftest.ini file, I get the waveform, I get the constellation, but instead of seeing a nice hump in the FFT graph a see a gentle horizon.

My process so far, was to install the board in the case, run LimeUtil --update which updated it to the latest and greatest firmware, the LEDs are correct (two on solid green, one blinking red/green) basically everything I would expect to be there. LimeUtil --find sees the board, that is all good, but I get that odd result with selftest.ini

Working with example.ini and tuning it to the FM band (100.7Mhz to be precise), I can see the stations, but I also get an occasional “jump” which looks on the FFT display as fairly wide (say 1 - 2Mhz) signals that jump on at a fairly high power level. Those last for just a blink of an eye and then go away. Don’t seem to be in the same place every time either.

My “old” or previous LimeSDR doesn’t exhibit these same symptoms. Which pretty much rules out software, driver, and cable issues (all the same in both cases).

So I’m trying to figure out what to look for to debug this.

–Chuck

2

Try an outboard power supply. It may stabilize it.

Ed

1 Like
3

Good suggestion, I did get it to run the self test correctly (woohoo!) The board is still a bit flakey though, sometimes LimeUtil --find doesn’t see it, and unplugging and re-plugging the USB plug will allow it to be found. The fan pins don’t seem to be supplying 3.3V (does the fan run only sometimes? or all the time?) The board it typically returning 50C as the temperature.

–Chuck

4

I went through this today. Worked on it all day. I reflowed the FX3 chip & all is stable.
Not sure if this is your issue, or not.

Ed