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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).

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  • Could you detail each connection you have made between the Pi and your kit? – joan Sep 26 '15 at 21:13
  • Acorrding to the BED schematic, there are pull-up resistors on the STEP and DIR inputs, so you should see something close to Vcc on those input pins when they are not connected. – Peter Bennett Sep 26 '15 at 21:38
  • @joan Updated question with additional info. – bheni Sep 26 '15 at 22:32
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    No one here is going to be able to answer your question, because we can't know exactly what you did or the quality of your wiring. In my experience these kind of problems are due to unexpected things like floating earths. If one of the boards was powered by 12v but not properly earthed it can put excessive voltage on the Pi. With these kind of projects it is important that the Common/0v of each board is solidly connected together and to the power. You could insert a 470Ω resistor in series with input to the Pi for extra protection. – Milliways Sep 26 '15 at 23:45
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    Did you power down your system while hooking/unkooking the drivers? Or did you hot-plug them while 5V or 12V was on? – Dmitry Grigoryev Apr 11 at 13:52

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