Saidly the stock situation has changed… PCF8575 looks like a good replacement but it would require changing the PCB as well as selecting other power supply IC.
As for your next question, you can of course use only the inputs and daisy chain another PCB. Or you can update the PCB and get rid off the output parts and replace them with optocouplers. This way you will end up with inputs only board
Wow, very nice design @pilotak !! I’ve been working myself on a much simpler design, less efficient as it uses a lot more ESP32 modules and switch ports to reach the same number of I/Os, but it is built on non specialized components that hasn’t been affected by the supply shortage. In case anyone is interested they are described here:
I’ll soon attach a permissive open hardware license to them.
EDIT: a next iteration will possibly bring the ESP32 to the main board giving the possibility to use more GPIOs.
Cheers
Tales
I was also thinking about replacing the digital IO expanders and use the classic multiplexer like CD74HC4067 and many others old fashion ICs. This will expand your IO range instead of using multiple ESPs and dealing with the pin requrements during setup. Those are available all time.
For driving relays NPN with diode will do as well. The reason why i have dedicated switch is because i can control 12/24V lights and other inductive/capacitive load directly without relays.
For optocouplers just use per channel instead of bunch in one package.