The CYC7C64743 microcontroller is outdated. There’s no USB driver for Windows 10 or Windows 11. It’s probably best to remove this part and replace it with something else.
The RF power sensor uses essentially an ADC with an SPI interface for reading the DC voltage of the diode detector and a I²C temperature sensor for temperature correction.
Maybe it is possible to use a small microcontroller board like a Blue Pill (STM32F103), an Arduino Nano or a Raspberry Pi Pico as a substitute for the CYC7C64743?
A Pico has the additional advantage of running Micropython on it, which could reduce the development time substantially.
Does a Pico fit into the space between the bottom side of the PCB and the bottom lid?
No, unfortunately there are two screws in the way! But they should be able to be removed without affecting functionality:
Now this looks better! The USB connector is still in the way, but can be easily desoldered. To protect the other components, I stuck on some Kapton tape:
To desolder the old controller without a professional desoldering tool, I took a piece of 1.5 mm² copper wire and bent it into a U-shape so that all pins had thermal contact with the wire. With this arrangement, the controller was easy to remove, even though it was also glued to the board:
After removing excess solder with soder-wick and cleaning the PCB from flux with some alcohol, the PCB looked shiny and clean:
In order to prevent short-cuts on the Pico, I glued Kapton tape to the bottom of the PCB:
What I tried next did NOT work:
I connected the USB data lines with short pieces of wire from the solder pads of the controller (pins 15/D- and 16/D+ of the CYC7C64743) to the solder pads of the Pico and the USB power pins to pins 14/USBVcc and pins9/10/Vss.
The PC reported a USB error!
What now?