Reprap driver pinouts

This is largely a memo-to-my-future self, but it may save some time for someone else facing what I was last weekend.

I’ve been putting together a Reprap recently, seeded by the purchase of a partially assembled one from someone local who was leaving town and didn’t want to take it with them.

One of the issues it had was that 2 of the stepstick driver boards it uses were burnt out, and in NZ there are no local suppliers – that I could find. There is however a supplier of Easydriver driver boards, which are apparently compatible. (The Reprap electronics is a sanguinololu, which has a fitted strip that exactly matches stepstick (or pololu) driver boards. The Easydrivers are not physically compatible, but they should be pin compatible.. no?

I mapped across all the pins carefully, and the only issues were: there are three GND’s on the Easydriver vs 2 on the stepstick, and the PFD pin isn’t exposed on the stepstick board so it can’t be mapped across.

I ended up with this mapping (I’m not sure where pin 1 is *meant* to be on the stepstick, so I’m starting with VMOT, the anti-clockwise corner pin on the same side as the 2B/2A/1A/1B pins, when looking down on an installed board pin 1, and going clockwise from there).

Stepstick – Easydriver

2B – B2
2A – A2
1A – A1
1B – B1
VDD – +5V
Dir – Dir
Step – Step
Slp – Slp
Rst – Rst
Ms3 – Nothing
Ms2 – Ms2
Ms1 – Ms1
En – Enable

But, when I tried to use this, the motor just jammed up solid.

A bit of debugging and trial and error later and I figured it out. The right mapping for the motor pins:

2B – B2
2A – B1
1A – A1
1B – A2

Thats right, the two boards have chosen opposed elements for labelling of motors coils pins – on the step stick 1/2 refers to the coil and A/B the two ends that need to have voltage put across them, on the easydriver A/B refer to the coil and 1/2 the two ends…

Super confusing, especially as I haven’t been doing much electronics for oh, a decade or so.

I’m reminded very strongly of Rusty’s scale of interface usability here.