I have tried using a board that contains an MCP23017 chip. It seems to work fine in verification tests on a Raspberry Pi 4 (test SW that came with the board).
There are a few things that I don't understand about the suggested settings:
1. Why is 'pin' set to a value of 9? A value of 'I2C' seems to make more sense.
2. When I add the line described in the hardware setting, I expected to get 16 more programmable 'zones' (relays) in the WateringPlan, whereas I get only one, called 'expPIN01'. The home page shows the same thing.
3. When I connect the hardware to the I2C pins, set the address, GND, VCC and one interrupt pin to GND, the Pi does not seem to send any I2C commands.
4. I expected to find a 'canned' setting for the 'expansion board' to be in the drop-down list at the top of the HardwareSetting page, but I don't see it in the list. If it were there, I expect that it would work for my board as well and might have solved my problem.
I fear that I don't understand somthing very basic. Can I get some advice from the Forum?
Images of the screens are below and the HardwareSettings as a pdf file.
Peter Dewdney
Good, I just updated the documentation after I received your comment so probably it was not your fault when you read it the first time 😁. Anyway thanks to your feedback now things are more clear.