SDR (Software Defined Radio) Transceiver

[ted051]

Pavel:
"You can find its description, installation instructions and SD card image at:

http://pavel-demin.github.io/red-pitaya ... ansceiver/

I would be very interested to know if somebody could test this SDR transceiver and post the results."

My experiences:
Today I had success with your new transceiver program, but only with the following settings:

LAN cable connection, static IP address: 192.168.1.101 using input1 without 50 ohms resistor, only 20 cm wire as antenna, frequency 17 490 000 (Radio China- very strong).
Receiving is acceptable, but not as good as with SDR# or HDSDR.
Interesting: changing rx_sample_rate to 50 000: "mouse- voices", changing to 250 000: "extreme bass voices"

Best regards, Wolfgang (DH1AKF)

[pavel]

Thanks a lot for the test!

Interesting: changing rx_sample_rate to 50 000: "mouse- voices", changing to 250 000: "extreme bass voices"

Looks like some of the GNU Radio blocks don't support changing of the sample rate at runtime. Using QT GUI Chooser block for the sample rate was not a good idea. I'll replace it with a simple Variable block in the next version.

[fbalakirev]

Hi Pavel,

I would like to be able to process (I/Q, decimate , filter, store ) ADC data in a continuous manner and at the same time be able to take a mutli-megabyte snap-shot of the raw ADC waveform on a trigger event. A natural way to do it seems to be to duplicate ADC stream via broadcaster and send one stream to processing logic and another to a packetizer/memory writer/HP port. As I understand it, the packetizer would put a back pressure on the upstream when it is not passing the stream through, and that would stall the broadcaster and, in turn, the processing logic. I see that broadcater can be configures to ignore tready, but that could easily lead to data loss.

I wonder if there's an elegant solution that you may suggest. One idea i have in mind is to split packetizer start logic from reset, so it will accept and discard incoming stream until a start input signal, then pass through pre-configures number of beats just like it does now, then continue accepting and discarding the input.

[pavel]

As I understand it, the packetizer would put a back pressure on the upstream when it is not passing the stream through, and that would stall the broadcaster and, in turn, the processing logic. I see that broadcater can be configures to ignore tready, but that could easily lead to data loss.

You are right, tready is needed to make data flowing from the clock converter (FIFO).

Adding a start logic to packetizer is a good solution.

Another solution could be wiring s_axis_tready to 1:

Code: Select all

assign s_axis_tready =1'b1;

Yet another solution could be to put broadcaster before the clock converters and ignore the first 32 samples (FIFO depth).

[fbalakirev]

You are right, tready is needed to make data flowing from the clock converter (FIFO).

Adding a start logic to packetizer is a good solution.

Another solution could be wiring s_axis_tready to 1:

Code: Select all

assign s_axis_tready =1'b1;

Yet another solution could be to put broadcaster before the clock converters and ignore the first 32 samples (FIFO depth).

I added another configuration parameter "NON_BLOCKING" to packetizer IP and modified s_axis_tready assignment as follows:

Code: Select all

  if(NON_BLOCKING == "TRUE")  
    assign s_axis_tready = !int_enbl_reg | m_axis_tready;
  else 
    assign s_axis_tready = int_enbl_reg & m_axis_tready;

so it works as before unless NON_BLOCKING == "TRUE", where it does not block upstream when not active, which seems to work for the design I would like to implement. I wonder if similar feature could be added to main tree.

[tony1tf]

Hi Folks and Pavel particularly
Let me introduce myself - I am Tony, G3OVH and have been using SDR for radio astronomy and amateur radio for some years now. I regularly use my UHFSDR with PowerSDR for amateur radio competitions on the 70 MHz band. I have a collection of Rx dongles - FUNcube, RTL, Airspy, STmicroF4 Discovery kit, and STM32sdr txrx. So it was natural for me to buy an RP, especially when Elektor had a superb cut price offer just. I had done a bit of Googling and saw that SDR projects were being proposed for RP, but until I found this forum, I had no idea how far you had got. I hope I can join this group and help with the testing. My software skills would probably be overstretched to help with the code, although I am also a big Raspberry Pi fan so the RPi2 and new touchscreen display look like an ideal companion to the RP. I have both and will start thinking about integration.
I have had some discussion on the Hermes-Lite yahoo group about how the slow RPi Ethernet port could perhaps be bypassed by the 2 x 1Gbps camera interface port, with suitable o/p from the fpga, and the same could apply here.
Anyway, enough for now - thanks guys - superb project.
Tony

[pavel]

Hi Tony,

Thanks for your interest in the Red Pitaya SDR project! Your help is of course very welcome!

I've just looked at the Hermes Lite V2.0 discussion that you mentioned and out of curiosity I'm wondering whether the LVDS lines on the Red Pitaya board (SATA connectors) could be used for high speed communication with Raspberry Pi.

I'm still thinking how to fit most of the SDR DSP into the Red Pitaya board and to use a tablet computer as a user interface. Currently, the WDSP library is running on the Red Pitaya CPUs and processing 20 kSPS I/Q streams and most of the processing for the spectrum display is running on the FPGA. But I'm not sure if it's a good combination. Your ideas are more than welcome.

Best regards,

Pavel

[makerkatie]

Hi. My name is Katie, I've just my got my Red Pitaya up and running, and I'm very interested in trying to get it working as an SDR Receiver. What I really want to do, is see if I can pick up the 29MHz beacon from the RS-15 Radio Sputnik satellite as it passes overhead - I understand it is (barely) alive still. Do you think this is possible using the RP? I'm on a very steep learning curve here, reading as much as I can on SDR's, and my dad (I'm 12) has offered to help me build an antenna.

[pavel]

Hi Katie,

It's an interesting project. I did not know that there are satellites transmitting in a range of frequencies that Red Pitaya can receive. Now, I want to try it myself

I've just done some reading about RS-15 and I'd say that it should be possible to capture its signal with Red Pitaya.

There is an on-line service that provides some information about RS-15:
http://www.satview.org/?sat_id=23439U

Please keep us informed about your progress.

Cheers,

Pavel

[makerkatie]

Pavel,

Thank you very much for the quick reply. I have a couple of quick questions:

1) Your software is an SD Card image - I have a spare MicroSD card, is it as simple as using the card with your image when I want to use the SDR, then switching back to my other card when I want to run the other apps and stuff I've already put on it? (never used a FPGA before, not sure how that is set up etc)

2) Do you have any suggestions for antenna's - there is too much information out there, we are currently looking at building either a long wire or di-pole type antenna - probably hang something between tree's in our back yard.

Sorry if the questions are really basic, got a lot to learn. Let me know if you pick up the RS-15 beacon first! Might take us a couple of weeks to get everything figured out.

Thanks
-Katie