I am doing my first steps with a TMC2209 V1.2 stepper motor driver and a NodeMCU.
I power the motor side via 12 V supply (12 V on the lower rails). In the circuit, this is represented by a 9 V battery)
And I supply the board logic voltage with a MB102 breadboard power supply (5 V on the upper rails).
The jumper on the lower rails of MB102 is disconnected.
I ran into the weird problem. My driver circuit will power up when I connect my NodeMcu to my laptop via USB. But the only things connecting them are the logic pins for "enable", "direction" and "step".
I subsequently disconnected pins and narrowed it down to the step pin, which is switched every 2000 µs.
So I am guessing the current from the "step" pin is enough to supply the driver a little bit. Even the LED on the MB102 is turning on. It's not enough to control the motor correctly though, because its just shaking.
But why can the driver be powered via its digital inputs?
Should I prevent this and how?
Should I disconnect the 12 V motor supply when connecting to USB?