Gordon's comments brings me full circle here. For tuning, reducing drive to limit power should be useful.
A "tune" button that lowers power temporarily for tuning, like that in every commercial rig I have ever owned,? could make that easy.
A bridge that feeds forward/reverse power info to the Pi would be a great addition and allow for the software to report SWR and protect the RF amp. Pi Picos are readily available for ~$5 which have 12 bit ADC and can do some local processing, then communicate to the Pi 4 by I2C. The Pico could even yank a Pi 4 GPIO? pin down to let an ISR immediately cut RF power if needed.
The Pico would be loafing along with this task and could easily do other low level tasks for the radio. Run the coffee maker?
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??? Bob? KD8CGH
Bob Benedict, KD8CGH