Hi all,
to make it clear from the beginning, I do not need assistance in resolving this error and read up on the troubleshooting guides and tests. I rather would like to know your ideas on what actually caused this to avoid it in the future.
Here's the current state:
- Device is an Arduino Uno R2, connected to a PC with Windows 7 x64 via USB
- Arduino does not boot. LED on Pin 13 does not blink -> No bootloader or defective atmega
- Device is recognized by PC on USB port and loopback test works fine
As far as these tests show, the board should be fine and can communicate with PC but the atmega is defective or missing a bootloader. Did I get that right so far?
Now what I did was the following:
I had Arduino running on 12 V external supply. I needed to change the sketch and upload again, so I connected the USB cable WHILE the 12 V external supply was running. As the Arduino should automatically switch USB power supply off when external supply is connected, I assumed that the device would just reboot and, running on external power, enable serial communication. It did reboot, but never came up again.
Before this, I was able to upload a sketch without problems.
Now why did I do this in the first place:
Following the adafruit tutorial to connect a RGB5050 LED strip to arduino, I connected a NTD18N06LT4G N-Channel, Logic Level MOSFET to my board, Source to GND, Gate to PIN11 (PWM) and Drain to the Blue Channel of the LED strip.
The 12V+ channel of the led strip was connected to Vin on Arduino.
See wiring: Adafruit Learning System
I uploaded the source code successfully to set PWM of PIN11 gradually from 0 to 255 and back to 0.
I disconnected the Arduino from USB and plugged in external 12V supply, rated 6 A. Sure enough, the strip lit up blue, but did not oscillate. I suspected that I should slow down the cycles and wanted to debug via USB port while external power is supplied, leading to this situation.
So what are your guesses? Is my arduino salvageable with a new bootloader? Did the IC go bye-bye? Was it because I had external power and USB at the same time? Or is my circuit bad?
Thanks for your thoughts...
Robert