Just fried a raspberry pi 2 using 4 of Big Easy Driver's from Sparkfun. Would love to know why it happened and how I can fix it.
Here is a link to the stepper motor drivers I'm using. This page links to their data sheet and hookup guide: Sparkfun Big Easy Driver (BED).
So I am building a cnc machine. I’ve hooked up 4 BEDs using recommendations from the hookup guide (See link above). I’ve closed the 3v/5v jumper, adjusted the POTs so that 3 of them supply a max of 1.3amps and the 4th will supply a maximum of 0.3 amps. I had all these working individually, I even had 3 connected without issue. But as soon as I hooked up the 4th it completely fried my RPi2 (Won't boot. Completely bricked).
The BEDs are all connected using a 12v 5.2A power supply. The thing is, when I disconnect EVERYTHING and connect a single BED to power (and only power) I see the DIR and STEP pins read 3.3v. I’m not sure why these input pins are reading high. I did a lot of testing and I don’t see any evidence of shorts. No idea how many mA they are putting out but was wondering if the cumulative current from the 8 connections (4 DIR, 4 STEP) could have fried my board.
So the question is, why did this happen, and how do I wire this so that the BEDs don't fry the RPi2? Do I need to put a resister between the RPi2 output pins and the BED input pins? Is there something else?
Really appreciate any help.
Update 1: There are 2 GPIO pins connected per BED. One for the STEP, one for the DIR (There are no resistors here, just straight connections). So 8 total GPIO pin connections. Also there is a single RPi2 GND pin (pin 39) connected to all 4 of the BED logic GND pins.
Then each BED is connected to a motor using the AABB pins. Finally the BEDs power pins (GND and M+) are all connected to a 12v 5.2amp power supply.
The remaining BED pins are unconnected (VCC, SL, RS, M3, M2, M1, EN).