Beagle/cape power problems


I have two Beaglebone 6As purchased from Lady Ada, and two OpenROV capes from circuitco. Neither cape will power either bone. I can get the bones to power at 5.5 volts with dimension engineering SWADJ3 switching power supplies or 7805 TO-220s (w/ a decent sized heat sink). I think the problem might be with the NCP349 on the bones. Anyone else having this problem?


That's strange... BB should power up at 5.0v (they should not need 5.5) Are you putting 12v into the OpenROV Cape?



Yes. Seeing that the cape is safe up to 40V, I ran it up to about 20 just to make sure that wasn't the problem. One thing I did notice is that the cape's voltages increased as the power input increased, but just not enough to get the cape to power up. That's not supposed to happen with a regulated switching power supply such as is on the cape.

Powers up with a 7805(linear) at 5V, but on a switching supply needs 5.5V - strange. I suspect the rise times of the switching supplies are somehow causing an issue with the UVLO/OVLO chip.

I'd like to get involved with the new board design that's been hinted at. I happen to own a PCB assembly line and I am almost finished with an Eagle layout for a board with the same functionality as the existing one.


After thinking about this a little bit more, I think I may know where your trouble is coming from. If you look at the documentation sheet called "BeagleBone OpenROV Cape Rev A1" (which can be found in the Electronics branch of our GitHub account here), there is a note above the 5v supply to the BB on page three that says "This wont be populated in Shield Adapter version VDD_5V comes from DC Jack on Bone".

You mentioned that you bought your Cape directly from CircuitCo, so I think it may be that your version of the Cape does not have the electronics necessary to power the BB.



I did see that in the schematics. Not sure exactly what "Shield Adapter" means, but it definitely powers it, just not enough get the NCP349 to close its connection from VDD_5V to DC_IN. I'll have a closer look when I get home tonight, but it definitely has a handful of very large inductors on the bottom of the board. Applying power to Header 2H creates power on the BB's 2.1mm jack. If none of those components were populated, I cannot see a path to the BB in the schematic - unless I am overlooking something.


Yep - just confirmed it - everything's populated except for a hand full of resistors cutting off the native Arduino shield headers.