I have a Protoneer board v3.51 and I just received my new XYZProbe today. I'm wondering how the probe hooks up to the controller board. Does it connect like an endstop? I was looking at an Instructables article that described setting up a probe (not the OpenBuilds one) on a Protoneer board and they described connecting the probe to the SCL/GND inputs on the board, not the endstop inputs. Where does GRBL expect the probe to be connected? The docs for the XYZProbe just say connect it to the "probe" pin on the controller, but I don't think the Protoneer has a pin they describe as being specifically for a probe.
Cross check the Grbl Wiki - it has the raw Uno pinouts (Probe is labelled there). See the Connecting page of github.com/gnea/grbl/wiki
Just to follow up, the probe pin on the Uno is A5 and it it is connected to the SCL pin on the Protoneer board. So, the instructables article I saw was showing the proper connection for any probe including the XYZProbe.
