LimeSuite TX mode and FFT viewer issues

Projects Lime Suite
1

In LimeSuite how do I know for certain that no transmit energy is being emitted?
I ask because despite turning off many widgets in various tabs, the FFT viewer calculates a TX data rate no matter what I do. Is there a definitive mode indicator?

I’ve looked at the block diagrams and so forth in the Programming and Calibration Guide.
Some specific things I tried turning off/disabling:

TRF tab
TXFE Output Selection → Disable ←
Power Down Controls | Enable TRF Module` → Uncheck ←

TxTSP tab
Enable TxTSP → Uncheck ←

I can see programmatically in lms7002m/LMS7002M.cpp:

int LMS7002M::EnableChannel(const bool isTx, const bool enable)

which includes this relevant section:

  TX “--- frontend ---“
    this->Modify_SPI_Reg_bits(LMS7param(EN_DIR_TRF), 1);
    this->Modify_SPI_Reg_bits(LMS7param(EN_G_TRF), enable?1:0);
    this->Modify_SPI_Reg_bits(LMS7param(PD_TLOBUF_TRF), enable?0:1);
    this->Modify_SPI_Reg_bits(LMS7param(PD_TXPAD_TRF), enable?0:1);

Leading me to believe that my choices in the TRF tab might be sufficient—the Enable TRF Module is associated with the EN_G_TRF parameter.

Back to FFT viewer:
I also think there are additional issues in the FFT Viewer code—
a) Every time I check Capture to file/Capture enable, when the FFT frame count has been reached, LimeSuite crashes.
b) And the FFT/sec rate indicator is always zero— is there a way to enable it?
c) Finally, I noticed that the tooltips in the rest of the GUI become inactive when the START button is pushed in FFT. There seems to be some kind of event loop/threading issue, as responsiveness throughout the GUI drops as well.

V17.01.1-PothosSDR-2017.02.04-vc1
Build date 2017-02-04
Windows 10

Thanks.
Tony

2

Hook up a scope, then you’ll know for certain down to your scopes lowest detection settings.

3

I did not want to run that kind of test for a couple of reasons, but I’m glad I did.
It revealed a concern and then further testing led to more concerns about LimeSuite.

I connected one of the TX ports to an inexpensive, but excellent analyzer and signal generator. (the picture shows the devices, but for a test using signal generation to LimeSDR RX)

tpi-and-rasdr4.jpg1632×838 387 KB

Without explicitly turning on TX elements, I measured -26 dBm (red line in picture below). This could be a problem for radio astronomy environments, but also is consuming extra power and generating extra heat as measured by the board controls temperature and other means. Turning off the TX elements is shown in the picture where the measured output drops to the measurement threshold of the TPI device (-55 dBm / yellow line).

tx-rf-test.PNG792×529 39.6 KB

What is also problematic is that the Quick Test(s) do not tell you that just loading one of the .ini files in LimeSuite turns on the TX elements. You don’t have to click GUI->Chip for TX to become active. Nor does closing/stopping the application turn off the TX elements. I’m hoping Lime @Zack @andrewback can update their documentation for these concerns, if I’m correct, and address the FFT viewer issues identified in my first posting.

There are at least three ways to turn off TX elements that I have discovered:

  1. From the TRF tab, uncheck Enable TRF module in the Power down controls section.
    (yes this is semantically confusing as are other “power down / enable” combinations).
  2. From the TBB tab, uncheck the Enable TBB module in the Power down controls section.
  3. From the TBB tab, reduce the Frontend gain to 0. (the gain value may be affected by calibration, so the scale for positive numbers is not fixed.)

LimeSDR v1.4s and LimeSuite 17.01.1 Windows 10

Tony

1 Like
4

That TPI unit it exactly what I had in mind as one of my ideas for the LimeSDR. Plus, it comes with software and a case already. If I had seen it before I would have one now and would re-engineer it do do some of the other things I want the Lime for. The two together is a powerful combination. Picture a box that they both attach to with mixers, amplifiers, filters, and switches, all under an umbrella program.

5

Hello @tony.bigbee
Do you know if the board itself has a default TX setting at power-on when you actually don’t load a .ini file and don’t use LimeSuite ?
I’m going to run some experiments using soapy_power (that doesn’t use .ini files) and would like to know what to expect…
mario

1 Like
6

Hi @mariocannistra,
The board appears to stay in whatever state you last had it when using LimeSuite. I don’t think there is a default TX power-on.

Tony