[gpsd-dev] GR-701W hangs on Pi-3

Hal Murray hmurray at megapathdsl.net
Fri Jun 3 05:30:23 UTC 2016

oliver at mutability.co.uk said:
> Do you trust your power? The Pi 3 is even more picky than the Pi 2.

Thanks.  That could be the problem.  Meter says 4.8V.  I didn't get out a 
scope to look for dips below that.

gem at rellim.com said:
> Everyone should have a USB V/A meter, they are cheap.  Here is one for $6: 

Beware.  Inserting a current meter will actually drop the voltage you get.  
You should probably get a real meter to see if the USB meter is showing the 
high side or low side of the current measuring resistor.

gem at rellim.com said:
> The Pi people say 2 amps is not good enough, they recommend 2.5A. 

That depends upon the stuff you plug into your Pi.  With a regulated supply, 
it doesn't help to have one with a higher current rating.  It might run 

In theory, each USB port can ask for 500 mA.  I don't know how much the Pi 
will give out.  Then you can plug in a HAT...

Adafruit says their wall wart style power supplies targeted at the Pi 
actually set the output voltage at 5.25 to give a little more room after the 
end of the cable.

> I have a USB Volt/Amp meter on my Pi3, never seen it pull more than 700 mA
> while compiling a kernel, and running gpsd, ntpd and the GR-601W. 

> 28AWG is 0.064 ohms per foot.  Double that for out and back to 0.128 ohms/ft
> of USB cable. 

0.128 * 3 * 0.7 is 0.268 V.  So if you start with 5V, you will be under 4.8.

Adafruit also has 6 inch cables.  :)

These are my opinions.  I hate spam.

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