Feature Request: Add Spectrum and Waterfall Display

[dedseclulz]

It would be really helpful to have a basic spectrum and waterfall view added. This would allow users to quickly scan the band and identify active frequencies more efficiently.

Thanks for the great work on this project!

[max-arnold]

Hello!

Do you have any ideas of how it could be done? According to the schematics, the audio signal is not wired to the CPU, so it can't process it.

[dedseclulz]

Maybe based on the S-meter? Of course, the quality would be worse, but at least some kind of visualization of the airwaves.

In the image, there's an example of the spectrum from custom firmware for the Quansheng UV-K5 radio.

[Hamberthm]

I also think this would be awesome, but don't know if it could be implemented cleanly.

I was just reading the SI4735 Programming Guide and it seems like the only way to get an RSSI reading on a frequency is by previously tunning to it. So unless the radio goes silent to do a quick sweep to collect the RSSI info on all the graph frequencies, and then back to the desired frequency, I don't see another way...