I finally had enough with this bug tonight and wanted to know exactly what makes a GOPRO HERO3 lock up when charging with some USB chargers. The tell tale sign that this has happened to your camera is the dimly lit back LED and no response to any button presses. So I finally hooked it up to my scope and had a looksie using the below setup. Basically, all I'm doing is powering the GOPRO HERO 3 via my benchtop powersupply and monitoring it with a multimeter and an oscilloscope. (Non techie may skip to the end)
What I found is this, many USB chargers are supposed to be 5V but without any load hover around 5.2V. Most consumer electronics deals with this fine, but the GOPRO HERO3 actually locks out. The camera at this point is either latches up or hopefully a software errors out on this event. At this point the only resolution is to pull the battery and reinsert to get the camera responding again.
Below is a good connect cycle at 5.2v. My scope is a bit off and that was actually at a 5.2v input. The ringing is most likely caused by the long lead of my probe ground, but the current spike is definitely there. I should also note that a wall-wart USB charger will ring more than a bench top. Please note that the spike is at roughly 7.32v.
Below is what happens when I bring the voltage up to 5.21v. As you can see a 10mv difference brought it up to an 8.36v spike! The current at this time is 180mA and thinking that is just flowing through a resistor or BJT back out to ground or perhaps even powering the camera which is now in a frozen state. I don't wish to take apart my camera to trace it. :-) Also, I don't have a current probe so I couldn't measure the current spike, but even adding a 100uf cap to the line didn't prevent the "overvoltage" lock from occurring.
So the moral of this story is it appears the GOPRO HERO3 is very sensitive to the USB Charger being used. The voltage can not reach 5.2 volts at steady-state or else it will lock out your camera! If your particular charger doesn't work, unfortunately find another. I've had a lot of luck with genuine Apple iPhone chargers and my laptop. Luckily, I also noted while charging, it only draws about 300mA of current. Therefore a 500mA charger and your computer should be fine. Because of how "chargers" compensate for current draw, you probably will be better off with a 500mA charger than a 2Amp (2000mA) charger.
If you like to test out yours with a multimeter please see this diagram and carefully probe pins 1 & 5 on the mini b side or 1 & 4 on the Type A side. You must see below 5.2 volts to prevent this lockout from occurring.
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