I've been using a power supply for an arduino project that was powering three arduinos. I accidently reconnected the arduinos with the voltage around 30V. One of the three immediately got fried, but the other two's LEDs are functional and they show up on my computer but won't allow me to upload a sketch. Each one gives me the can't open message. Do you think I've just fried them as well?
Yuh. Sounds like you seriously abused the power supply, which will often trash the board. The 16u2 that they use as a serial converter seems to be very easy to burn out if you do something bad to the power supply (particularly while it's plugged into USB), and it's in a no-lead package that's very hard to replace.
The 16u2 seems to be the weakest link (other things that often blow are the '1117 regulator, and the '358 opamp that they use for the power switching circuit). Interestingly, the 16u2 seems to be more prone to failure of this sort than the cheaper serial adapters used in many clones.
Thanks guys, definitely going to be more careful next time. This 16u2 is interesting though. Is it on pretty much every arduino board? I have another Nano that wasn't connected to the board when I fried everything, because it's been giving me that error message for a while now. Do you think it could be that 16u2?
Nano uses FT232, not 16U2