Which Particle pins are used for control?

Sorry, I’ve been through the docs, and I still don’t understand which pins on the Photon are used to push commands to the relay controller chip. I am using the Photon on a 4-relay board with the NCD4relay library.
This one: 4-Channel DPDT Signal Relay Shield. I had some LEDs connected to D0 and D1 which didn’t work, so I am suspecting these two, but some other diagrams I saw show the serial pins used for SDA and SCL. I am not using the I2C out port at all.

Is there any way you could post a photo of your setup? We can probably see the problem immediately in a photo.

Thanks for the help. I am trying to code for the 4-relay board, but I don’t have the board yet for testing. I will very soon.
I see from the mechanical board drawing that D0 and D1 are indeed used with the Photon. Those pins correspond with D1 and D2 on the Electron. It’s strange that there are no pinMode() calls in the example firmware.

There is no need to make any calls to set pinMode since the Wire.begin() call does that itself.

Did you order the board with the IOT interface socket here which has a socket the Photon/Electron can plug directly into:

Or did you order this board:

If you ordered the second board did you order one of our I2C particle adapters here:

Just trying to get an idea of what you have. You really don’t need to worry so much about the IO lines, just know that SDA and SCL lines are connected to the MCP23008 IC on the board which drives the relays.

Good question. It was purchased by my client and as I understand it, it is the IoT interface version.
I don’t really understand Wire methods so I can’t tell from reading the library which pins are being used.
My understanding is that I don’t need any connections to onboard GPIO pins because the drivers do it.
However, having a sensor connected to some pin on the Photon causes a problem if that pin is in use by the relay controller, right?

That’s correct, just make sure you do not use the D0 or D1 lines on the module for anything else as they are used for I2C communication to the MCP23008 IC on this board, you can use any other pins you like.