Driving Mega2560 from external 5V bricks USB port

Using Arduino IDE 1.x
16

After another hour of experimentation I found something that worked:

The following instructions are for Macintosh/osX (Lion), with the Arduino IDE 1.0.0 installed in the applications folder.

  1. Plugin a usb cable to the arduino mega rev3 in order to supply it with power.

  2. Plugin an avrispmkII programmer into the 6 pin icsp1 jack located adjacent to the usb connector (observe pin1 orientation via the dot on the board).

  3. Open a terminal window, paste in the following command and execute it:

/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/avrdude -C /Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/etc/avrdude.conf -p m16u2 -F -P usb -c avrispmkii -U flash:w:/Applications/Arduino.app/Contents/Resources/Java/hardware/arduino/firmwares/Arduino-COMBINED-dfu-usbserial-atmega16u2-Mega2560-Rev3.hex -U lfuse:w:0xFF:m -U hfuse:w:0xD9:m -U efuse:w:0xF4:m -U lock:w:0x0F:m

  1. Unplug both the programmer and the usb cable, then plug the usb cable in and the mac (and the pc) should recognize the usb port as long as the arduino mega rev 3 is KNOWN TO BE GOOD.

Note that I had to alter the '-p' device code to 'm16u2', AND I had to use the .hex file that was contained in the arduino IDE's firmwares folder which was 21kb - The one I downloaded from git hub was 93kb, I have no idea why, but I do know that the instructions above work for me.

NOTE THAT THESE INSTRUCTIONS DID NOT REPAIR THE BOARDS THAT I THOUGHT WERE DAMAGED HOWEVER.

In one case the programmer indicated there were verify errors and did not restore the dead board.
In another case the programmer indicated the burn was successful but again did not restore the board.

The reprogramming only worked on the board that I bricked by apparently erasing the 16u2, or uploaded bad firmware.

Thus it still appears to me that I have 3 dead mega's and no clue as to WHY they're dead. Per-the-above-help, I have verified that the external regulator puts out a nice steady 4.98 volts both loaded, and unloaded and ripple is within the OKI-78's specifications.

Anybody have any other thoughts on the matter?