4 Arduinos Down :(

  1. Uno gives error when compiling:
Binary sketch size: 1,084 bytes (of a 32,256 byte maximum)
avrdude: verification error, first mismatch at byte 0x0042
         0x9d != 0xbf
avrdude: verification error; content mismatch
  1. Mega 2560 USB Device Not Recognized error in windows

  2. Mega 2560 does absolutely nothing when plugged in it's as if it isn't plugged in

  3. Mega 2560 same as 3

This really sucks. This is a lot of money. These boards die on me once a year. This is over about 4 years and I've lost them all. They seem to work fine until I have them externally powered at the same time I am uploading a sketch via usb. The first two times it happened I didn't realize that was the problem. Then I started to think about it. So the next one I used I never did that. Until last week. I did it by accident. And soon after that, It gave me the USB Deice Not Recognized error. As far as the UNO goes.. I let that sit in a drawer and barely used it so I think that one is fine if you guys can just help me with that error code. I'm using 1.0.3 and yes I select the correct board. Has anyone else ever had this problem? This is ridiculous. It seems as if the only thing wrong is the usb device. Is there an alternative way to program these that is just as easy through ICSP maybe?

Have you seen this rather long thread about bricked 2560's using external power and USB at the same time: http://arduino.cc/forum/index.php/topic,82046.0.html

If you don't want to read the whole thread, you can jump to final answer here: http://arduino.cc/forum/index.php/topic,82046.msg758170.html#msg758170

See page 10 re: protection diode


TI part is not used, I think a NXP part is, whomever the actual source is has similar statement on their datasheet.
I think added this diode from output to input would prevent this bricking.

Awesome info guys. Thanks. I'll look into it. I was actually powering it through the power jack with 12V.