Powering beaglebone black via P9 header pins

[robpar...@gmail.com]

Hi There,

I have been working on a project using a beaglebone black which I am trying to power with a 3-cell LiPo battery. To do this, I have connected the output of a hobbywing ubec 5V-3A voltage regulator to pins P9_5 and 6. This seemed to work well for a while, but just now the BBB abruptly turned off and will not turn back on. I have tried disconnecting everything from the BBB and connecting it to my PC with the USB cable. This results in a quick, faint flash of the PWR led followed by nothing. Pressing the power button with the USB cable plugged in yields the same behavior. I just tested the voltage regulator output and my voltmeter reads 5.3 V. My understanding is that the BBB requires a well regulated 5 +- 0.25 V power input. So technically my power supply is 50 mV above the limit. Is it possible that I have fried the board by doing this? Is there any way to recover it without buying a whole new BBB? Thanks in advance for your help!

[gra...@flex-radio.com]

The single blink means that the Power Management Chip is going into self protect.

You need to put a scope on the output of your regulator and see what is going on.

5.3 V will not fry the BBB.

It would run fine from a 5.3 V supply that never went above 5.5V

But it will respond the way you describe to short transients that go above 5.5 or below 4.5.

There is also a rise time spec on the start up Voltage rise.

Or, it could mean that something else did fry the board, such as a blown I/O pin, which is causing an over current protect on the part of the power management chip.

The single blink does not tell you what is wrong, just that something is wrong, and the power management chip is still alive and doing its job.

--- Graham

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[Rob Parsons]

Thanks for your reply. I have scoped my regulator output and it shows a steady 5.38 +- 0.05 V. Besides the power pins, I only have connections to P9_19 and 20 to use i2c2 bus. The thing that really worries me about this board is that when I remove all connected items, and attempt to power with the USB only the behavior is unchanged. (faint flash of power led then nothing)

In my system I have i2c from the BBB communicating with an arduino which controls a stepper motor. That's it. In my mind this is fairly simple. I'm not sure how I could have killed the BBB this way. Should I just try to RMA the BBB?

I know it is difficult to diagnose the issue without seeing the specifics of my setup so I appreciate your help.

[gra...@flex-radio.com]

With everything disconnected, and a simple USB cable for power acts the same, points in the direction of an over current shutdown due to shorted IO on the BBB CPU.  

If you can RMA it and get another, I would try that.

You need to examine your application and make sure that all I/O pins are operated within Voltage and current limits, and the inductive "kick" from your stepper motor is not getting back, somehow, into the BBB I/O.

--- Graham

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