Here is how my I.F.R. firmware development board looked like once I added the code to show current A/B/C functions:
This modification makes the I.F.R. to work exclusively on the 817, not on 857/897, so I will add a configuration option to exclude this function.
As a side note I understood how the FT-817 CPU handles the current F-menu setting. On the RTX, when F is pressed the current menu page is displayed. If SEL is rotated the new menu page is not saved to the internal EEPROM, until A/B/C or F are pressed: FT-817 display returns to Signal strength meter, and the I.F.R. can display the new page.