Re: Goto off

George Cushing

Tearing my hair out on this for s few weeks trying to build motor cables. So I dug into it and seems to me that the problem of driver outputs goes back to the original Allegro Micro Demo board's design. The A4988ET IC was laid out with four outputs for bipolar steppers. Pin 24 was Channel 1 OutA (1A), pin 21 was Channel 1 OutB (1B), pin 28 was Channel 2 OutA (2A) and pin 1 was Channel 2 OutB (2B). Where 1A /1B connected to the motor's coil A and 2A/2B went to coil B. When laying out the Demo board it was easier to present the pinouts in the order of 2B, 2A, 1A &1B. 

Then Pololu Electronics came along, grabbed the A4988ET and designed their motor driver carrier. In doing this they adopted the pinout odder of the Demo board, that is,  2B, 2A, 1A &1B. Pretty much all the succeeding drivers followed their lead. A notable exception is the ST820 from FYSEC.

This pin layout is a bit counter intuitive in that the first connection reading down the carrier is the last connection of the stepper. The confusion this engenders is made only worse by the use of various step motor makers to designate the motor inputs using A+/A-( A/B, A'/A, A/B, etc.) for the first coil and B+/B-, etc for the second. 

Here's my cue card for the drivers I use. TMC2130, 2209, 5160, A4988, DVR8825 and LV8729.

Join to automatically receive all group messages.