A4988 Stepper Motor Driver Carrier - cannot pulse the step line with Photon

I have the ‘Blink an LED’ program running on my Photon. D7 led blinks. I connected D7 to the STEP pin on the A4988. I noticed the voltage at that pin the collapses to around 1V and the LED does’t blink either. It should be around 3.3v. I unplugged power from the A4988 and it still happens.

WEIRD! I figured the STEP input on the A4988 was high impedance. Even with it unplugged from power, it still happens. Doesnt this seem weird? Anyone have good or bad experience with the A4988 Stepper Motor Driver Carrier from Pololu? I think I may have got a dud. Any input is appreciated!

Brian

These boards are so simple there isn’t a lot to go wrong with and I’ve not had problems with my Pololu shields so far.
To check whether the board is a dud or not you could just tap the step pin with a jumper wire to 3v3 and see what happens.

But for a question like yours we’d usually expect to see your code and how you’ve wired the system.

For sure. Welp, I bet I fried it. I realized I had the 12v motor voltage connected to the input voltage pin as well as the motor voltage pin on the driver. After connecting the voltage input to 4V, It still collapses the voltage on the output pin of my microcontroller but I could have caused a short inside from connecting it to 12V. I have a second driver one I will try connecting tomorrow. :blush:

Brian