dr_d_gee
Posts: 84
Joined: Fri Jan 04, 2013 1:30 pm

Pi 2 video problem

Sun May 10, 2015 11:24 am

I'm having a problem with my Pi2 when it's connected to my HD monitor via a KVM switch. A small, bright multicolored square about 1cm square appears not far from the top right corner of the display shortly after the machine starts booting, and remains there until it shuts down, even when the X window desktop is showing (Raspbian OS).

This does not happen with two different Pi1s connected via the same KVM switch, running either Raspbian or RISC OS.

What's causing this and is there any way to cure this problem?

User avatar
rpdom
Posts: 15583
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: Pi 2 video problem

Sun May 10, 2015 12:46 pm

The small coloured square is a warning that the Pi isn't getting enough power. Either the output of the power supply isn't enough, or the micro USB cable is not good enough to handle the current required. The red PWR LED will turn off as well.

The square appears if the voltage drops below about 4.65V, which is outside the safe range for the Pi2. Try a different PSU and power cable.

The Pi model B doesn't have this feature, so you get no warning if the power is low. The B+ does have the warning. Also the Pi2 needs more power than the Pi1, so a supply that works well on the P1 might not be good enough for the Pi2.

dr_d_gee
Posts: 84
Joined: Fri Jan 04, 2013 1:30 pm

Re: Pi 2 video problem

Sun May 10, 2015 3:06 pm

It doesn't happen without the KVM switch. Since it takes power from USB it must be demanding too much from the Pi. I'll try another power supply or maybe introducing a powered hub. Longer term I probably need to look at an independently-powered HDMI switch of some kind.

Thanks for a VERY helpful reply—knowing what the problem is helps in solving it!

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