You are correct, the speed is not my biggest concern, but I would like to operate the device using a web interface.
The advantage for me is the integration of BT and WiFi.
The embedded SPIFFS filesystem allows local storage of HTML pages, without need of SD cards. And that for approx $4 (Aliexpress)
Hardware design is tested and ready, 1 thing to do on the Analog input port.
Digital imputport protected using an optocoupler
More details on the following page: https://wimnijholt.nl/projects
The current Arduino sketch can be used, just adapt the pin numbers.
On the link you find the details regarding GPIO ports used.
And one new include.
The development of the code is on its way leaving the original code almost untouched. Just added some hooks to the web part. I hope I can show you the results in short while.