Hi all!

A strange problem came up today when I switched my MKS Gen L for a BTT SKR v1.4 Turbo. For my stepper motors (1.7A) in combination with my LV8729 stepper drivers (R100) I need a Vref of about 0.68V (where the max Vref for this stepper is around 0.75V), so I had set the adjustment screw in the correct position for this (did this a few weeks ago on the MKS Gen L board).

However, after simply switching the stepper drivers onto the new (SKR v1.4) board the value of Vref is now suddenly 0.48V. I tried to turn the screw to increase the voltage but as it already was almost at its maximum I can't increase the voltage any further than 0.55V which is too low for my motors. Does anyone know what the problem could be here and how to fix this?

Note that I ordered 2 BTT SKR v1.4 Turbo boards and the same occurred on both of them, and I also tried this with 5 different LV8729 stepper drivers without any change in result.

UPDATE: So I just tried my DRV8825 stepper drivers and these seem to be working just fine, so it has to be something with the compatibility with the LV8729 drivers as I just checked them on my Gen L board and they're still working fine on that one...

Edited 2 time(s). Last edit at 07/23/2020 07:54AM by CaptainJackas.

DRV8825 is a fairly difficult technique. So you should be careful to operate it. good luck.

I think it's unfortunate, but SKR 1.4 provides 3.3v instead of 5v to the drivers. The same problem occurs with A4988. I solved this by cutting the VDD pins of the drivers and soldering wires that I connected to one of the several terminals that supply 5v on the board.