Dear Ivan,
I’m extremely impressed by your code and documentation! 
- I wonder: Why isn’t it listed as ‘1 click installable binding’ at OH2 ?
- What is the difference between the other MQTT bindings listed there?
After reading everything I had to realize:
- it does not seem to support PCF8574 8GPIO I2C expansion boards.
So I did not install it yet.
How much work would it be to enhance your code to be able to handle this board too?
https://www.waveshare.com/wiki/Raspberry_Pi_Tutorial_Series:_I2C#Control_PCF8574_IO_using_i2c-tools
Is it possible that you could do it and I would pay for it? If yes, how much would it cost me?
I’m not a rich guy at all (my programming rate is 10-15$/hour) but I don’t like to ask for favours for free.
Why those boards?
- Very cheap
- easy to connect 8 of them in a row
- has jumpers easy to change Address IDs 0-7
- Available at my County from stock
- Already bought 8 (need 64+48 I+O port. Later maybe more…)