Lime Mini - Data Wrong (IgnasJ)

Hi Ignas,

Here’s an issue I can’t get to the bottom of, it only affects the Mini. I can start a stream and sometimes the data is almost right - but isn’t, there are spurs every ~ 12kHz apart (maybe this is a clue):

By simply setting the LO frequency again the data is then correct:

I have diagnostics enabled at level 4, nothing is being reported. Somehow the data delivery part of the Mini has a bug. In this case the sample rate is 12.288 MHz, LO 103.5 MHz but this can happen at any sample rate / LO frequency.

I’ve looked at the stream status, no data there indicating problems. Once the Mini is streaming properly it works well. I’m sure this is probably linked to other issues that have been reported.

Note: once the Mini is streaming correctly setting a new LO frequency does not cause the problem shown in the first image, it’s only when starting the Mini.

I changed the stream to the values you use but this makes no difference, it really seems to be in the data delivery part of the board.

The Lime USB works very well indeed, this is only a problem with the Mini.

Tagging @IgnasJ.

Just to get more info:

  1. As I understand you use Rx and the spurs do not appear/disappear when changing LO frequency, correct?
  2. Do they appear/disappear just after starting/stopping stream (without (re)setting sample rate)?
  3. Does board cooling has any effect? (i.e. using fan vs not using fan)

Hi Ignas,

I get the spurs when starting the stream, if I change the LO frequency while streaming this fixes the problem, even just a change of 1Hz can fix it. The board is cool, it’s in free air @ 16C.

I can start at 24MHz and when running properly it will continue to run all day. Once started OK it stays OK and works well.

I’ll help any way I can.