[Exnor]

(26th Apr, 2015 01:14 AM)marcello Wrote:  

(19th Feb, 2015 08:34 AM)mansp Wrote:  

(19th Feb, 2015 01:23 AM)Exnor Wrote:  Is this data sheet usefull for you?

I did pick up a new micro usb cable today that was shorter, an old sony cable. It was perhaps half of the length of the old one that I have been using, and now the rainbow square is gone. So I guess that the cable was the weak link here. I am however stuck with my original problem, that the TV switches to the other hdmi source unless I plug the cable in that port.

Hi Mansp,
I got into quite some undervoltage issues too, and finally traced it back all the way to cheap micro USB cable's. I lost up to 0.25 volt for just the cable when feeding the more powerhungry Pi2, and usb stick and wifi.
5 Volts 2.4 amps is easily printed by 'less educated engineers' or their marketing buddies.
But providing a stable PSU for the Pi2 needs just a bit more than a cheap phone charger and cables you got lying around.
I have learned it the hard way too, and corrupted quite some SD setups in the process.
But Hey, I powered the pi2 ( and bplus ) from the TV and streamed heavy content which needed audio processing for output though the TV while it was rescanning the server library :-).
A 2 amps power supply that outputs just up to the max of 5.15 volt even at the rated max current does the trick for me, without changing the cables.
greetz M

If you have access to an oscilloscope and multimeter you can "debug" all that very fast...

Plug the PSU output to the oscilloscope to see how stable is the output.. if you see too much harmonics or even worse if the output wave is not near flat, then you have a crappy PSU that might not deliver the stability that the Pi 2 needs.

To test if the PSU is feeding the necessary amps you need to use the multimeter...