I have a setup where RPi may join existing I2C -bus as master when powered on. Before taking over, it will first notify secondary master with "slave select" -line so that the bus becomes free for taking.
The RPi is hardwired to the bus. Problems is that its SDA/SCL -pins doesn't seem to be open as I expected when RPi is powered off. I thought it would be fair to expect this since this would also mean that RPi used as I2C slave would also block the whole bus if powered off. Doesn't sound very nice...honestly I think this can't be true and I've just screwed up something.
So what am I missing? Or do I have any other options than external switch controled by RPi's 3v3 between RPi and the bus?
EDIT: The board is Raspberry Pi Zero W 1.1 (BCM2835)