Bad Atmega8u2 chip, possible to still upload via ftdi cable?

I accidently got a 12v wire mixied up with a output from the 5v rail on my arduino uno and fed 12v back into the 5v rail.... Everything is still functional but the Atmega8u2 chip(looked like i was emeril for a moment, cooked it like a roast). the current sketch still runs fine, the output voltage from the reg is correct, so i beleive that the only part damaged was the actual 8u2 chip. Now my question is without replacing the 8u2 chip can i use a ftdi cable of ftdi breakout board to upload sketches into the main chip? Is there going to be any ill effects backfeed signals and power into the smoked 8u2 chip?

Thanks zack.

Looks like the UNO doesn't have the FTDI connector holes like some earlier models but you should be able to wire it up and use it to upload.

Black - Ground --- GND Brown - CTS Red - Vcc -------- +5v Orange - RXI -------- D0 Yellow - TXO ------- D1 Green - DTR --||-- Reset (100 nF cap?)

yea there's no standard ftdi six pin socket on this one, that's what kinda made me almost think that there was no bypassing the atmega chip, i have tryed it several times like the way you listed and couldn't get it to work and thought i was missin something.... I was i forgot to set of the reset pin. lol. hopefully this works so i can still use it till the new chip comes in.

cheers!!! zack

If the auto-reset doesn't work, just hold down the reset button till you see the "Binary sketch size" message to do it manually.

tried it both ways... still no dice. may be time to just get another uno and make a breadboard version with this one. bummer

thanks for the help!! zack.

Now i have completely removed the 8u2 chip and still can't upload anything to the board via a ftdi breakout. I'm going to order a new 8u2 chip this week but wanted to see if there was any other way of loading code into the main chip first, because if something else is messed up i don't want to waste the time and effort into putting another 8u2 on the board.

thanks for the help, Zack.

Another way is using SPI via the SPI pins.

Grab a USBtiny programmer, one is available from Adafruit for $US 22 :

http://www.adafruit.com/products/46

They are useful to have anyway, for uploading bootloaders etc.

If that doesn't work you may have fried your Atmega328 chip (or parts of it), but that should be replaceable.

I’ve def been looking into getting one of those actually, my question is whats the dif between that programmer and this one?

http://cgi.ebay.com/USB-ISP-Programmer-ATMEL-AVR-51-ATMega-ATTiny-/160589596203?pt=LH_DefaultDomain_0&hash=item2563e2c62b

Or this even this one

Obviously the adafrat one also includes a 10 pin cable but as far as programming these few atmel chip we use what does one do that the other doesn’t for me?

Thanks zack

rsxpeed7: I've def been looking into getting one of those actually, my question is whats the dif between that programmer and this one?

http://cgi.ebay.com/USB-ISP-Programmer-ATMEL-AVR-51-ATMega-ATTiny-/160589596203?pt=LH_DefaultDomain_0&hash=item2563e2c62b

Or this even this one

http://www.sparkfun.com/products/9825

Obviously the adafrat one also includes a 10 pin cable but as far as programming these few atmel chip we use what does one do that the other doesn't for me?

Thanks zack

The first one has a 10-pin cable, the Uno uses a 6-pin one. You would need an adapter.

The second one looks like it has a cable with both 6 and 10 pins.

Bearing in mind the need for the adapter for the 10-pin cable (or make your own) both should be fine.