Lime SDR mini V2 - Support for hire

General Discussion
1

I have a demonstration coming up. I was going to do with the Lime SDR V2, but I need some expert support in order to make it happen otherwise I will have to try the Ettus B205. Is there any expert out there who can answer some in depth questions?

Thanks,
M-

2

Hi, I can answer software related questions, and some, but not all hardware related.

3

I need to understand how to correctly set the antenna for the Mini V2. Does it need to be set manually for each different frequency , or can one set it to AUTO and it will automatically pick the right antenna for the frequency?

I setup all the parameters, and before starting streaming data (TX and RX) I run the LMS_Calibrate. I set both the antennas to the same frequency in an effort to get loopback working, but I cannot get lock. Related to this I set the gain on TX to 40 and the gain on RX to 10. I don’t want to fry any components… What should the power settings be?

I am working on a test that does loopback. I have tried both a RF cable from RX to TX and two antennas.

M-

4

BTW I can run this same code using an Ettus Research B205 and it does get lock. So it is specific to the Mini V2.

5

Here’s an example that transmits a chirp signal and receives it over antennas: LimeSDR Mini V2 loopback chirp · GitHub

gain settings are relative to the maximum power, and the maximum power is different at various frequencies, so there is no correct answer, what power settings should be used, without knowing other parameters.

6

In the sample code for chirp… I see that he treats bandwidth = samplerate…

…
if (LMS_SetSampleRate(device, sampleRate, 4) != 0)
error();

if (LMS_SetNormalizedGain(device, LMS_CH_RX, 0, 0.4) != 0)
    error();
if (LMS_SetNormalizedGain(device, LMS_CH_TX, 0, 0.6) != 0)
    error();

if (LMS_SetLPFBW(device, LMS_CH_RX, 0, sampleRate))
    error();
if (LMS_SetLPFBW(device, LMS_CH_TX, 0, sampleRate))
    error();

LMS_Calibrate(device, LMS_CH_RX, 0, sampleRate, 0);
LMS_Calibrate(device, LMS_CH_TX, 0, sampleRate, 0);

…

Is that correct? We calculate bandwidth differently. Should I treat them as equals?

M-

7

bandwidth does not need to be equal to sample rate. You can set any bandwidth according to your needs.

8

ricardas… thank you for your responses. I have a software stack with drivers for various SDRs at the ‘bottom’ of the stack. I use a USRP B205 and the software stack works with a specific radio configuration. I replace the USRP driver with the Lime SDR driver using the same settings and the software stack does not work (it looses lock). I modeled the Lime SDR driver after the USRP driver filling in the APIs ( set_tx_frequency, set_tx_bandwidth, etc. ) with the LMS_Set… APIs. And I setup the stream like I did USRP. Still no luck. I have gone through the lime driver several times, but don’t see any glaring errors. Do you have any suggestions? thanks…

9

I switched to 16-bit samples (was previously 12) and things are working better. thx.