MCU error 3 (SXR tune failed) on LimeSDR USB

#1

Hi!

I wanted to check LimeGPS project, but was unable to do this. Right now I’m facing calibration issues when running it:

Opening and initializing device...
Reference clock 30.72 MHz
Sample rate: 2500000.0 Hz (Host) / 2500000.0 Hz (RF)
Calibrating...
Tx Calibration: MCU error 3 (SXR tune failed)
Warning: Failed to calibrate device: Tx Calibration: MCU error 3 (SXR tune failed)
Setup TX stream...
Creating GPS task...
Using static location mode.
xyz =   1335616.6,  -4648136.6,   4144388.5
llh =   40.785092,  -73.968285,        10.0
     8.382e-09   -7.451e-09   -5.960e-08    5.960e-08
     8.806e+04   -3.277e+04   -1.966e+05    1.966e+05
     1.86264514923e-09   3.55271367880e-15     233472      1987
    18
Start time = 2018/02/04,00:00:00 (1987:0)
...

As a result I don’t see any transmission of GPS signal. Is there a wiring mistake or some issues with hardware?

P.S. platform: Windows 10, gw version 2.21. LimeQuickTest shows everything is ok. LimeUtil --timing shows same MCU error 3 or MCU error 5.

Thanks.

#2

Doesn’t look like it’s been updated in around a year and so may not work with the latest version of Lime Suite. The best thing to do would be to raise an issue on the GitHub tracker.

#3

Thanks @andrewback . I also tried gps-sdr-sim, an updated version of LimeGPS, and have same issues.
Anyway I still interrested what could cause this “MCU error 3” to raise during TX calibrartion. Seems like it related to RX calibration. Also I have same errors also in LimeUtil --timing during ‘TX corrections’ and ‘RX corrections’ loops. The latter shows ‘MCU error 3’ or ‘MCU error 5’.

#4

@IgnasJ perhaps you could advise.

#5

I’ve checked this through LimeSuite and I’m getting the same error, when trying to set 1575.74 MHz in SXT tab (Calculate + Tune) and pressing ‘Calibrate TX’ in ‘Calibrations’ tab after.

Edit: although a lot of other frequencies are calibrated without issues.

#6
  1. Does setting frequency in SXR tab to around the same as in SXT (~1575MHz) work (Calculate+tune does not produce errors)? If it still does not work then there may be something wrong with your board or power delivery.
  2. Do you always get the error or only when the board is cold/heated up?
    Also, press “Default” button before setting frequency in SXT/SXR tab to make sure the board is not in some unknown state.
#7
  1. Typically no. I’ve tried several times and ‘calculate+tune’ worked fine. The issue only rise during calibration on specific frequencies.
  2. The behaviour is always the same and doesn’t depend on board temperature.
#8

I do not get that error message in the LimeSuite GUI, could it be that you are doing something different. Below is exactly what I did to try and recreate your error message. Maybe I’m not doing something that you are.

  1. I run Limesuite.
  2. I press F1, and the version shown is 19.04.0
  3. I goto Options->ConnectionSettings
  4. I select/highlight my device and click on Connect. At the bottom of the display I see “LimeSDR-USB FW:4 HW:4 Protocol:1 GW:2.21 Ref Clk: 30.72 MHz”.
  5. I click on the “Default” button, to put the board into a known good state.
  6. I select the SXT tab/leaf and in the “Frequency, MHz” box I type in 1575.74 and press Calculate and Tune.
  7. I select the SXR tab/leaf and in the “Frequency, MHz” box I type in 1575.74 and press Calculate and Tune.
  8. I select the Calibrations tab/leaf and click on “Calibrate TX” and a click OK pop-up alert box saying “Tx Calibration Finished” appears, to which I click OK.
  9. Still in the Calibrations tab/leaf I click on “Calibrate RX” and a click OK pop-up alert box saying “Rx Calibration Finished” appears, to which I click OK.
#9

Actually on screenshot above a result of similar procedure skipping steps 7 and 9. For other frequencies results could be successful. But several others show such error during calibration.

#10

I’ve checked one more time: there are several frequency ranges I’m unable to ‘TX calibrate’, but ‘RX calibrate’ works fine. E.g. 30 MHz, 400 MHz, 790 MHz, 1575 MHz.


Also here is my LimeUtil --timing output where I saw the first signs of the issue:

C:\Program Files\PothosSDR\bin>LimeUtil.exe --timing
Connected to [LimeSDR-USB, media=USB 3.0, module=FX3, serial=0009060B0046220C, index=0]
Creating instance of LMS7002M:

Timing basic operations:
  >>> SPI write register:       177.698 us
  >>> SPI read register:        185.737 us
  >>> TSP NCO setting:          1309.33 us
  >>> RFE gain setting:         374.987 us
  >>> TRF gain setting:         742.616 us

Timing tuning operations:
  >>> CGEN PLL tuning:          25.8269 ms
  >>> RF PLL tuning:            70.7425 ms
  >>> TBB filter tuning:        91.8032 ms
  >>> RBB filter tuning:        148.211 ms
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
Tx Calibration: MCU error 3 (SXR tune failed)
  >>> TX corrections:           88.194 ms
  >>> RX corrections:           167.179 ms

Done timing!
#11

The issue does not seem to affect all boards/setups as I am unable to replicate it. That is why I suggested that it may be power, temperature or defective board and wanted to make sure that we use same settings (loaded by ‘Default’ button).

It is strange that SXR tune works from SXR tab but not during calibrations. Maybe @Karolis or @ricardas could provide some insights on that, as they have more knowledge of how MCU calibration works.

#12

Any suggestion what I should do with my board?