It is a knob indeed. I have started tests of a quadrature rotary encoder connected to my (Interactive) Frequency Reader development board. This extension will allow to tune the FT817 as if we were rotating the main knob on the front panel.
The firmware is able to read the rotation direction and increase (decrease) the VFO frequency accordingly. I am having troubles with fast rotations, something that should be mitigated with the use of a larger knob or a less sensitive encoder. I would like to avoid the addition of a binary divider between the encoder and MCU.