hi guys,

trying to set up my rpi zero w with pixhawk as per these insructions: http://ardupilot.org/dev/docs/raspberry-pi-via-mavlink.html

did a quick test to see if I get power by connecting power via usb to pixhawk ONLY and I don't seem to get anything.

am I assuming the wiring from a "large" raspberry pi would be the same for the zero?

to  clarify I have connected the +5v but no power being drawn.

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David, did you ever figure out your issue? I'm trying to do the same thing. 

The image is meant for a RPI3, not a RPI zero. That might be the issue.

So after some research the wiring is the same for rpi3 and zero, has anyone got the zero to work?

That's terrible insane advice - never power the raspberry from the pixhawk.  That's an error in the docs and should be fixed.  Power the raspberry from a BEC or USB, separately.

Fnoop, first time I've heard this, can you explain a little? I've powered a pi3 this way before but didn't know it was a bad idea. Are you able to explain your setup?

Firstly the telem2 port in that diagram is a lower power port, the telem1 port is 'high power' as detailed here: 

http://ardupilot.org/copter/docs/common-telemetry-port-setup-for-ap...

but can still only handle up to max 1a and is still not a good idea to go up that high - and a raspberry can easily exceed that if you push it (max cpu, wifi, anything plugged into usb) particularly if powered directly through the 5v rail which has no limiting, unlike the usb.  If you're just using a pi zero on it's own then you should be fine most of the time, as it draws a lot less power.  I think that doc page was created back before the raspberry had quad cores, wifi etc which consume a lot more power.

The main problem is if you draw too much power then you will affect the voltage available to the pixhawk itself and risk suffering a brownout, where the voltage drops to a point that the pixhawk can no longer function.  Then your craft drops out of the sky.

So it's strongly recommended to power anything significant from a separate power source.

Well thanks for that fnoop, anything that can cause a catastrophic failure is obviously not a good idea, do you know if there is an official or advised way to power the pi3? As I'm struggling to catch your drift with powering from bec (as you can tell I'm no pro)

Most of us are amateurs-in-learning :) (I certainly am).  You can buy a 5v BEC from any drone/hobby shop, as long as it does 2-3a that will take care of anything a raspberry is likely to consume.  A lot of PDB (power distribution boards) for your ESCs these days have 5v BECS as well that will power a raspberry.  Yes a zero is powered through the GPIO pins the same as any other raspberry, so should work.  Make sure you have the right pins connected (!) and you have the ground connected.

If you can, power the raspberry through the USB as it has polyfuses and other protection that the GPIO power rails don't have - it's a little safer for the raspberry, but a bit harder to wire up as you have to cannibalise a USB cable.

Thanks again fnoop, helpful as always. I don't suppose you have any info on the usb  cable conversion?

Hey, it's actually super simple.  Take a normal usb2 cable, cut in half, take the small plug half and strip the outer sheath where you cut it.  You'll end up with something like this:

https://electronics.stackexchange.com/questions/183218/can-the-data...

Then just connect the + and - from your BEC to the black and red wires of that bit of the usb cable.  Really simple, and gives your raspberry some protection from spikes, reverse polarity, incorrect voltage etc.

Awesome, thanks a ton!

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