Switch back to internal clock reference

ameyar · 31 March 2023 19:17

Hi,

I am wondering how to switch back to the internal reference once i am done using an external reference. My SDR application no longer works when i disconnect the external reference. I have basically connected a 10 Mhz external reference and clicked the following in LimeSuite GUI

Also, i checked the documentation for ADF4002, but not able to figure out what ‘LCM’ value means. Do you happen to know what that means?

My external reference again is a stable oscillator at 10 MHz sine wave, with Vpk = 1.4 V. I notice once i do the calculate R,N & Upload the LED on the LimeSDR USB goes green. So that tells me that there was a lock with the external reference source.

Thanking you in advance!!

Sid

andrewback · 1 April 2023 13:05

Should do this if you simply reset the SDR, or do you mean without having to do this?

Also I have moved this post to its own topic, as it has nothing to do with XTRX.

ameyar · 1 April 2023 14:30

Thanks for your response. No a simple reset should be fine. I did restart the computer which should reset the LimeSdr USB, but that didn’t do the trick.

I don’t think there is a reset button on the LimeSdr USB is there? Or is there a jumper pin which i need to flip and back?

Maybe i should wait a few seconds between disconnecting the USB 3.0 and reconnecting it?

It could be the software suite(srsRAN) not switching back to the internal reference once it locks to an external reference. Have you heard something like this where the application refuses to go back to internal reference once its find an external reference?

I tried GQRX for good measure to see if its receiving anything after i did the restart and it was working just fine(without external reference connected).

Also, i followed the following articles and posts to connect an external reference. But none of them tell on how to go back to the internal reference.

Post 1
Post 2
Post 3

andrewback · 1 April 2023 14:48

As soon as it has lost power, it should forget it was configured for an external clock.

Unlikely, provided srsRAN is not configured for an external clock.

OK, so this proves that it’s working fine with its internal reference. If when using srsRAN it does not and expects an external reference, the problem is your srsRAN configuration.

ameyar · 1 April 2023 15:03

Got it. Thanks. Yeah, it’s probably something with the srsRAN configuration as you pointed out. It’s somehow not working with the internal reference anymore, so i am guessing there is some configuration that got flipped.

Reminder: Do you know/were you able to find out what that ‘LCM’ value means in LimeSuite GUI?

andrewback · 1 April 2023 15:18

I’m sure @zack could clarify, but generally speaking LimeSuiteGUI is for development and low level debugging and is probably not something you should need to use.

Zack · 3 April 2023 07:05

LCM is Least Common Multiple. It is calculated here:

github.com

myriadrf/LimeSuite/blob/master/src/ADF4002/ADF4002.cpp#L283


      
              m_registers[11] = ctemp;
          }
          
          /** @brief Calculates R N values from frequency
          */
          void ADF4002::CalculateRN()
          {
          
              double x = txtFref*1000000;
              double y = txtFvco*1000000;
              double Fcomp;
              while((x!=0) && (y!=0))
              {
                  if(x >= y)
                  {
                      x = fmod(x, y);
                  }
                  else
                  {
                      y = fmod(y, x);
                  };