MightyHat Power output with Pine64 [SOLVED]

[BenCranston]

Quick question on the MightyHat..  If' I supply it with 5v at 2.5A will it be able to provide that current "downstream" thru the Pi?  The application is for a Pi with an external USB Hard drive.  In addition to the HD, the MightHat with the Moteino and RFM69 radio, I'm planning on having a XBee, Z-wave USB stick and potentially a Bluetooth/WiFi dongle...    you know me, something on every port.

I'm currently running the Pi with the 5v @ 2.5A power supply, USB Hard Drive, Moteino w/ RFM69HW, Z-Wave USB Stick -  all without issue.  My hope is to move to the MightyHat for cleaner integration of the Moteino and the benefit of the LCD display.

Thoughts?  Thanks!

[Felix]

I haven't tried it but given the parts specs I think a pass through should be OK. However if power is cut it won't be able to deliver 2.5A of 5V from a LiPo battery.
The MHat was designed to power the Pi (keyboard, HDMI etc) and not much more. Any power hungry devices should be powered separately.

[BenCranston]

Ok, so a follow up question..  Can I disable the MH's back power into the Pi?  I've been looking about for a schematic and can't clearly see how that might be done.  Basically reverse the power flow.  Instead of the MH providing power to the Moteino and the Pi.  Take power from the Pi and power the Moteino.  I'd still leverage the buttons to turn on and off the Pi, but not leverage the power boost in the MH.  I know it's silly, but logically it's a possibility.  My preference is to have the MH manage the LiPo and power supply into the Pi including supervision, but if I have to go the other direction with power and have the MH feed off of the Pi I'd like to know how.  Thanks.

[Felix]

Not really, the power path and digital circuitry is behind several blocking mosfets and diodes. The main purpose of this board is to provide power to the Pi, while taking care of the battery management and backup. The power input moves from the Pi uUSB to the MHat uUSB.

[BenCranston]

Well, that settles it then..  Power path is *from* the MightyHat to the Pi, period.    I can work with that.  Besides, I'm pretty sure I don't need more than 1.5A of 5v to make the entire thing work.  Or at least without doing the math I believe so.  915MHz radio, Moteino, LCD, Pi, Z-Wave USB stick, WiFi & Bluetooth & ZigBee on the Pi.

I'll attach photos when it's all assembled.  I have to adapt a board to make the stand offs and thru-holes work from both the Pi and the MightyHat.  Ok, its not a Raspberry Pi, its Banana Pi Pro, Hence the mounting hole adaptation.

Oh, any chance you'll be posting the schematic for the MightHat?  Thanks again Felix!

[BenCranston]

Well, after much hiatus here is my adaption board for the MightyHat to connect to the Pi2 port of a Pine64. 

[BenCranston]

And a few more photos..

[BenCranston]

So now I come to the fun part...  If you carefully look at the MH you'll see that +5v always on jumper is soldered..  that's because is a moment of confusion I plugged the power into the Pine64 with the MH attached.  "that's funny I didn't think the MH would be able to source power from the Pi2 interface, hum..." and in that moment at least one FET was sacrificed to the gods of stupidity and the MH cannot switch the power anymore to the Pi2 interface.... ugh.

So, Felix, can you recommend a trace or which component I can lift off the board to take the damaged stuff out of the circuit and limp along?  Thanks.

[Felix]

Hi Ben,
So you're trying to power your new target (Pi compatible) or just use it with the MHat?
I think what youre saying is you had the "5V* ALWAYS ON" jumper soldered. This means as long as the MHat has input power, it would power the target Pi (or 5V* pins) permanently - this is OUTPUT fromo the MHat not INPUT to the MHat. The MHat gets its power from the uUSB/battery and can also be powered from a 2.1 jack from the bottom.

Otherwise can you take a more step-by-step approach and explain what exactly happened?

[BenCranston]

Sure thing...  So the plan was to use the MH to power the Pine64 via the Pi2 interface just like the MH would have powered a Pi2.  I had to build an adaptation board given that there are not compatible holes to mount the MH to the Pine64.  That's the tan perf board you see in the pictures.  Anyway, I plugged my 5v2a power supply into the MH and the Pine64 didn't not boot.  Expected..  The default script on the MH was waiting for me to hit the power button.  Hit the power button and power started to flow to the Pine64.  It didn't boot.  Unplugged everything and checked again.  same process - still no boot.  So then I said, "maybe not getting enough power via the MH so I'll move the power to the Pine64 input and see if it boots.  Nothing.  but the MH booted up from power supplied from the Pine64.  Interesting I thought.  It was then I discovered the uUSB card was not fully inserted so it wasn't going to boot.  moved the power back to the MH and tried again.  now when I push the power button the power goes on for a moment and then everything resets on the MH and the power goes off on the Pine64 again.  10th of a second type thing.  Great..  I fried a component with the back power from the Pine64.  So, with no Pine64 attached to the MH, the button works correctly but with a load it just reboots the MH.  I solder jumpered the always on bridge on the MH and that's how I'm working right now.  Working is a relative term as there is *something* damaged on the MH and I'm limping along with the jumper bridged...  So back to the original question, sans schematic, I'm at a loss of where to begin trouble shooting what I damaged.  hence the question of an easy cut or component lift that would stabilize things.

[Felix]

Ok I see now. So it's working with the solder jumper.
The MHat might be OK even if backpowered although I don't think I ever tried that
Try this - there is a through-hole capacitor pad where you can try soldering something like a 1000uF capacitor (6.3v spec ok, I'd go with 10v). Your Pine64 might need too much inrush current for the MHat to boost at the startup instance, hence you see the 10th/second behavior then everything dies. It just can't provide the power. Try solder the capacitor then try it again, let me know what happens.

See this thread for a similar situation.

[perky]

Maybe an NTC inrush current suppressor on the power line might also help?
Mark.

[BenCranston]

Are those thru-holes immediately to the right of the 5v always on jumper as viewed from the top of the board? (Antenna to the right and FTDI port to the left)  I see two holes that would accommodate a small capacitor, one with a + symbol next to it.

[Felix]

It's this:

[BenCranston]

Most Sweet.  I see it.  those were the holes I was thinking.  The MH is soldered to the header so I can't remove the adaption PCB to see under the MH board anymore.  perfect.  One capacitor coming right up.  Thanks Felix!