I got most of the electronic pieces together on the bench today - upon power up the arduino kicks off both stepper motors for a time until stopping with the AL002 error. From looking at the code I can’t see why it would want to move at all from the start. Anyone else run into this? I’m assuming that this is unexpected given the AL002 error.
This is most probably the homing function kicking in. The Arduino is moving the steppers till the optostops are triggered (homed axis).
I assume ( @azisi would know better) that AL002 is homing unsuccessful 
Ah ok, I don’t have the optostops looped in to this yet (still waiting on those PCBs, missed them in the first order)
speaking of which - where do they tie in to this?
Looked at the code and .sch - to answer my own question here for posterity:
the “SW” block on the satnogs pcb (J3) is for each of the end stop boards (Signal, gnd, vcc)x2