Lms7002m agc/rssi

Hello Lime,

We are trying to setup high power PA and LNA on LimeSDR for the LTE project.

We want to know how to make use of the on-chip AGC. Is it controlled by the RSSI automatically, or do we need to configure in LimeSuiteGUI?

I know there is an option in srsLTE to choose rx_gain automatically, but we are not sure whether it talks with LMS7002 well since there are too many intermediate layers like Soapy.


You might find the following helps:

For MCU AGC testing, there is an option (checkbox) labeled 'Enable MCU
AGC ’ in LimeSuiteGUI ‘TRX Gain tab’.

From code it can be started/stopped using LMS7_Device::MCU_AGCStart()
and LMS7_Device::MCU_AGCStart() functions:

The code that is executed when toggling ‘Enable AGC’ checkbox in
LimeSuiteGUI can be found here:

LMS chip settings can not be changed while MCU AGC is running, so MCU
AGC should probably be started after finishing configuring the chip.

Thanks Milo, will try that.

…actually thanks to Lime’s team. They’ve shared these information with us in the past :slight_smile:

After reading the documents. I still have some doubts.

According to LimeSDR Made simple series 2. There are 3 stages of amplifiers in the receiving path. primary LNA, RxTIA and RxPGA. Which amplifier stage is the MCU_AGCStart() function actually tuning? And this MCU_AGC is based on the digital rssi instead of the analog rssi right?

It uses LNA and PGA stages, and it’s based on digital RSSI

Thanks Ricardas!

Hello Milo,

I enabled the AGC checkbox in LimeSuiteGUI, and then I put a walkie-talkie nearby the LimeSDR, but when I move the walkie-talkie around, the amplitude of its signal on fftviewer is always changing. It is supposed to be maintained almost as constant right?

How do I evaluate the effect of AGC?


It seems to be a version problem.

I was using LimeSuite 18.01 and AGC isn’t working properly.

Now I am using with LimeSuite 18.04 and 18.06, the AGC is working now.

I tested for LimeSDR-USB with walkie-talkie, now it really maintain constant power level regardless of distance. But LimeSDR-Mini seems not supported yet.