I want to change from the good old noisy A4988 to the supposedly quieter MKS LV8729. So I disconnected my steppers, replaced the stepper drivers, set vref/current, connected the steppers again, shutting off the power before each step.

Unfortunately, none of my LV8729 output any stepper voltage or current, the voltage between the A1,2 and B1,2 pins is ~0V. In consequence, none of my stepper motors work, they don't hold their position without any input and don't react to controls either, obviously. The stepper drivers are correctly oriented.
I'm baffled, really. Any ideas?

The board I am using is Generation 7 Electronics 2.0 ARM [reprap-diy.com] with teacup firmware.

Update: By chance I noticed that all LV8729 work as long as I have at least 1 A4988 driver on my board. As soon as I replace all drivers with the LV8729 I get no power at any motor, and if I keep at least one A4988 I get power on all motors. How can this be? It should be a board-related issue then?

Edited 4 time(s). Last edit at 04/28/2018 06:18PM by Fivefold.

I have similar LV8728MR drivers and I have to invert the enable signal in firmware. Maybe that's also the case for your drivers?

That seems to have done the trick. They work fine now, although not quite as silent as I have hoped, even with 1/128 microstepping. Still a major improvement compared to the A4988s. Thank you!