Configuration of LimeSDR for GPS signal data collection

#1

Hello Everyone,

I am new to LimeSDR and LimeSuite. I need to collect GNSS signals using LimeSDR as a frontend.

I have already used frontends like RTL-SDR and USRP with GNURadio for the same purpose. But LimeSDR looks a little different. What I understood after reading its documentation is, we need to configure LimeSDR via LimeSuite GUI in order to make it receive GNSS signals. And this ‘.ini’ file goes into the LimeSuite Sink (RX) in GNURadio.

Now my question is:

  1. Can I just use the ‘example.ini’ file from this link and modify the frequency and sample rate according to my requirement?

  2. Where can I set the format of data that I am going to collect? (for example, I want the data in the format of ‘int8’).

Any help will be appreciated.
Thank you!

#2

@priyankap - Priyanka,

Please look here -----> Running your LimeSDR on GNSS_SDR on Ubuntu 17.10

Let me know if you need anything else -

73 de Marty, KN0CK

#3

Hello @martywittrock,

Thank you for your reply. I have used this already for my USRP front end. And it worked fine.

But now I don’t want to use gnss-sdr, I have my own software program for GNSS signal processing. So I just need to configure my limeSDR for Galileo data collection. And I need to store the collected data in a file.

Can I still use this ‘.conf’ file to configure my LimeSDR?

Because previously, I was using USRP with GNURadio to collect and store the data. And I want to do the same with LimeSDR and GNURadio. But when I use LimeSuite Sink(RX) in GNURadio it asks me for a ‘.ini’ file(which is a configuration file for LimeSDR) to set it for data collection.

Now my question is:
Can I convert this ‘.conf’ file to ‘.ini’ file in order to use it in GNURadio?

Thank you.

#4

Hello @priyankap,
To answer your questions:

  1. Yes you can use the ini file and modify frequency and sample rate, thought that might be a little bit difficult as you would need to modify those variables in LimeSuiteGUI save it and load it through grc blocks.(Loading ini file through functions is not supported in gr-limesdr right now).
  2. You can not change the output format of LimeSuite Source (RX) block but you can use other gnuradio blocks such as Complex to IChar to have it changed to int8.

You can only use that “.conf” file to look at what parameters they are using, you cannot use the file without using gnss-sdr.

To store collected data in a file you can use flowgraph diagram such as this:

Keep in mind that “.ini” file is not required and you can set up sample rate, frequency gain etc. in the block itself.
To read more about gr-limesdr you can read the following : https://wiki.myriadrf.org/Gr-limesdr_Plugin_for_GNURadio

#5

Hello @Garmus,

Thanks a lot for your reply. You have almost cleared all my doubts. Yes, I had already gone through the link that you sent me. The only thing that worried me was the ‘File’ section in LimeSuite Source (RX) block. But as you said, it can be empty. I just need to set the centre frequency and sample rate in the GNURadio blocks.

Now just a small question: (I am sorry if it is too naive)

  1. Regarding the output format, ‘Complex To IChar’ block changes the complex data from LimeSuite Source (RX) to ‘int8’ by default or do we have to set something to obtain ‘int8’ as the output format of this block?
  2. Also, where can I find the output format of LimeSuite Source (RX)? like is it 16 bit complex IQ or anything else?

Thank you again for your helpful answer.

Regards,
Priyanka

#6
  1. Yes that block changes the data type to char (8 bits int), though I don’t know if you are going to lose some data by doing this conversion.
  2. You can read about GNU Radio data types here: http://blog.sdr.hu/grblocks/types.html
#7

Thanks a lot.

Will read this!

Regards,
Priyanka