I configured the PCF8575 expander board the same way as your OS Expander – address 0x24, Vcc=EVIN from OS expander connector. I added a RED LED with 220R series resistor to test 8575 outputs. The schematic is the same as of the exp30DC.
There is a strange problem:
When I start the OS along with the expander, all expander outputs are H, which os OK. Then I force the ZONE9 for 10 seconds and the LED goes ON, but when the 10s period is over, the LED doesn’t goes off?! The software says it is off, but it is not.
The other issue is that just ZONE09 ( first zone of the PCF8575 ) is “working”, the others not.
Any idea what could be the problem?