Re: What a solution for Smeter?
You can have an S-meter without the 2nd nano with the version of CEC that you have, but you need to build a simple amplifier to take the audio from the high side of the volume pot to drive a diode and capacitor circuit. That 0-5v (or less) output feeds to A7 on the nano. You then can use the Memory Manager program to calibrate the S-meter at different voltage levels. It even has a way to automatically program, but I found it better to use my own numbers so that the readings matched what I saw on other radios. The descriptions are applicable to all displays, including the Nextion, that are supported by the CEC sketch.
Here is the description of a simple sensor circuit:
Here is how to calibrate the meter with the MM program: