Optocoupler in Roto Toolboard

[Jords27]

Hello everyone. I was looking at the Roto Toolboard schematic and saw that IO3 isn't routed to a connector. It is routed the same way as the other IO pins, but where the other IO pins route to a connector, IO_3_IN is connected to GND through an optocoupler. The optocoupler is continuously activated by the 3.3V supply. Wouldn't that then mean that IO_3_IN is continuously pulled to GND?
Thank you all in advance once again.

[dc42]

@Jords27 it's not an optocoupler, it's an optional IR proximity sensor, which is not fitted on the board as shipped but can be added by the user. It's the same as for the TOOL1LC board except that there is only a footprint for one proximity sensor instead of a choice of two. See https://docs.duet3d.com/Duet3D_hardware/Duet_3_family/Duet_3_Roto_Toolboard#adding-an-io_3-reflective-optical-sensor.

[Jords27]

@dc42 Thank you, that makes sense!