I recently resurrected a “fried” arduino NG. I thought it might be useful to give the details, in case anyone else runs into this.
The ATMega is a very tough chip. I burned out a voltage regulator and the FTDI chip, but the microcontroller was just fine. So here I am with my arduino board that is currently unusable because of two bad components.
Well, the power is not that big a deal. The voltage regulator is only used for external power, to get +5v. If you use USB power, an external regulator, or just replace the regulator, all is well.
The loss of the USB chip is more critical. Without some way to program the NG, it’s still a brick. You could use an ICSP programmer, buy a new arduino or get a Serial-TTL converter. Better still, get a USB-TTL cable. That’s what I did (I was getting a boarduino anyway).
The USBTTL cable has a 6 pin interface. PWR and GND are easy enough. There is also TX and RX which go to pins 0 and 1 of the arduino. But what about the other two pins? Those are the CTS and RTS signals. The CTS can be tied to ground. But the RTS should be tied to the reset pin. The newer board have a header for the reset pin. The NG does not. However, one of the lines for the ICSP is tied directly to the reset pin. I crimped a female molex pin to a wire and put it on pin 5 of the ICSP.
Diagram (of sorts)
USB-TTL pin Arduino pin
GND (Black) ---- gnd
CTS#(brown) ---- gnd
VCC+5(red) ---- 5V
TXD(orange) ---- Pin 1 (tx)
RTS(yellow) ---- reset pin (pin 5 of the ICSP header)
RXD(green) ---- Pin 0 (rx)
The wire colors on your cable may differ, read the schematic carefully. If you have a board that has the reset pin brought out, you can use that instead of the ICSP pin. Be sure to have the pwr jumper set for USB.
I hooked up my Arduino NG (that has no FTDI chip now) like this and it works fine.
Hope this is helpful.