Hello, I am attempting to build a 20x9 tri-colour LED matrix using a mega2560, I decided to use 6 AS1107 LED Driver chips and I also bought a 12v 1 amp external power supply to power the arduino.
When I was attempting to test the setup of the 6 cascaded chips I had the arduino powered externally and plugged into my laptop through USB, the arduino started to heat up badly and even started smell quite awful, I unplugged the arduino from the wall and as I did the laptop reset. the laptop works fine, but when I plug the arduino into it now it gives the message "USB device not recognised" and won't do anything. The arduino still quite happily draws power and even powers other things through the 5v lines but I cannot get it to communicate.
Ick. I accidentally hit my ATmega328 yesterday with a quick 12V pulse (from a battery pack, was experimenting with LEDs and constant-current driver chips) and my Macbook spontaneously powered off, after recovering everything I found my Arduino wouldn't talk anymore either, couldn't program the fuses or write the bootloader with an AVR-ISP mkII either. It was cooked. I'm pretty much betting yours is too, especially if you smelled smoke.
It was easy for me to remove the DIP package from my arduino NG board and swap in a new one (have 9 spares...) and burn the fuses/bootloader, but the Arduino Mega has a surface mount processor, so unless you're handy with SMT desoldering and can buy a new $12 ATmega2560 or ATmega1280 chip you're probably looking at a whole new Arduino Mega board.
Actually rereading that a little closer, I'm not sure what you just saw--you said it was plugged in externally and USB connected? Shouldn't the external power source get regulated down to 5V by the built-in voltage regulator? Not sure why you had that happen now.
Do you see any evidence that the Arduino's processor can still perform its logic and operations (i.e. is the sketch still running and blinking LEDs?)
Maybe it's just the USB interface chip that died...
The arduino still quite happily draws power and even powers other things through the 5v lines but I cannot get it to communicate.
When connected over USB or through external power?
First, disconnect all hardware from the Arduino.
When plugged into USB only, is the Arduino recognized and accessible (try reprogramming it.)
Do the 3V3 and 5V lines both measure correctly?
Physically, in between the USB port and voltage regulator is a Poly Fuse device. Measure the voltage (relative to GND) on both sides of that device while powered. Then measure the direct voltage drop. When you disconnected your external power, you had a sudden surge of current through USB. It is possible you damaged the Poly Fuse.
spirilis:
Do you see any evidence that the Arduino's processor can still perform its logic and operations (i.e. is the sketch still running and blinking LEDs?)
Maybe it's just the USB interface chip that died...
The sketch was sadly not actually working when it happened, so I've no idea if it's still trying to do what I programmed it to do.
[quote author=James C4S link=topic=71548.msg534103#msg534103 date=1315320913]
When connected over USB or through external power?[/quote]Using USB power, I haven't tried external power again.
When plugged into USB only, is the Arduino recognized and accessible (try reprogramming it.)
Windows doesn't recognise it at all, it gives an error saying "USB device not recognised" and doesn't assign it a COM port.
Do the 3V3 and 5V lines both measure correctly?
Physically, in between the USB port and voltage regulator is a Poly Fuse device. Measure the voltage (relative to GND) on both sides of that device while powered. Then measure the direct voltage drop. When you disconnected your external power, you had a sudden surge of current through USB. It is possible you damaged the Poly Fuse.
I don't have access to the arduino at the moment but I will test this tomorrow and get back to you.
"Windows doesn't recognise it at all, it gives an error saying "USB device not recognised" and doesn't assign it a COM port."
Sounds like a dead ATMega8U2 chip.
Once confirmed, and if the 2560 is still good, you can try removing it from the board, and wire in an extermal CP2102 module or FTDI Basic kind of part instead.
is the power led on? if not it may be a problem with a power switching transistor. Also if the led is on try to connect the board to another computer and check is it identified (some time ago I had that problem with standard mega and connecting it to my second pc solved the problem oO )
For those asking, the 5v line gives 4.79v, 3v3 gives 3.3v. This is using USB power. Using external 5V gives 5.02v, 3v3 gives 3.31v
Relative to ground the side of the polyfuse near the ATMega2560 gives 4.81v and the other side gives 4.91v. Over the polyfuse itself it gives 0.10v on USB power. External gives 1.76v on both sides of the fuse.
CrossRoads:
Sounds like a dead ATMega8U2 chip.
Once confirmed, and if the 2560 is still good, you can try removing it from the board, and wire in an extermal CP2102 module or FTDI Basic kind of part instead.
This is what I thought when it happened, is there a way to confirm if the 2560 is still good or if the 8U2 is blown?
The power led is on and I've tried using a different computer, no dice.