TDD mode and SoapySDR

laflamj · 17 May 2018 18:01

Hello everyone,

I want to use my Limesdr in TDD mode with SoapySDR (python) and i want to know if they exist any example/tutorial who explain how to switch in this mode and how you use it…

Thanks !

laflamj · 22 May 2018 00:55

Anyone have a example in C++ how to switch in TDD mode for the the limesdr ?

andrewback · 22 May 2018 08:33

@IgnasJ do we have one?

IgnasJ · 22 May 2018 11:08

There is no TDD mode selection. However, if you configure same frequency for Rx and Tx then a single PLL will be used for both.

mzs · 22 May 2018 12:08

Did you read this thread ?

laflamj · 25 May 2018 17:45

Yes but is not really clear to me how to do it…
They use probably the LMS7002M API… I’m using the SoapySDR API and I don’t know if i can use the two API in the same time in my c++ application…

My goal is to use the same PLL for the RX and TX for a ground penetrating radar application. I just need to synchronize the PLL for the RXMIX and TXMIX…

Can you help me to achieve that with one of the API ?

Thanks !

mzs · 26 May 2018 18:04

Ok maybe I was not clear and assumed far too many steps, but if you look at what is suggested in the above link and then search through the soapy API code and see if it has already been implemented:

Which it has:

github.com

myriadrf/LimeSuite/blob/master/src/lms7002m/LMS7002M.cpp#L2531


if (ratio != 7)
    interface_Hz /= pow(2.0, ratio);
return interface_Hz/2.0;
}


void LMS7002M::ConfigureLML_RF2BB(
const LMLSampleSource s0,
const LMLSampleSource s1,
const LMLSampleSource s2,
const LMLSampleSource s3)
{
//map a sample source to a position
std::map<LMLSampleSource, int> m;
m[AI] = 1;
m[AQ] = 0;
m[BI] = 3;
m[BQ] = 2;


//load the same config on both LMLs
//only one will get used based on direction
this->Modify_SPI_Reg_bits(LMS7param(LML1_S3S), m[s3]);

And then check when, where, or if EnableSXTDD is being called by the soapy API:

And then you just need to make sure that your code does what is required before ::SetFrequency is used.

i.e.
Configure same frequency for RX and TX and make sure that the following is true, which it should be unless you are doing something more complex.
abs (freq + cF_offset_nco -center) <= 0.1 Hz

laflamj · 11 June 2018 15:42

Thanks all for the information, I will try this