Why is or are PCF857x IO expansion modules always low trigger for output? I have got several different types of PCF857x modules and relays, and I was trying to find a combination of low relay open, high relay close, to avoid creating NPN circuit complexity, to invert the low/high logic, but it appears that can't be done with any of the canned PCF857x modules you can find on ebay or amazon?
I can find and have relays that are dual trigger, and this works great when driven by direct GPIO, depending on the jumper settings of course. But not when an i2c PCF857x module is used? I have tried, and the i2c PCF857x modules never signal low to high when pin is set for output, they only signal high to low.
This appears to be something related with how the i2c PCF857x pins default to input, i.e. initialize high by default? Read somewhere that i2c PCF857x modules typically (always by my experience) only generate an interrupt on input by high to low sequence, never low to high sequence.
I am right on this, or does someone have different experience? Tackled low to high logic without creating custom board/module?