I accidentally fed 12v DC to the 5v pin of Arduino Nano. Now the atmega chip gets very hot within some microseconds. But, com port shows up and board gets connected. It ends up with 'uploading' status in my PC and not further. I have 4 of them here in this condition. Am i done with these boards? Or is there any way to fix these?
If you fed them 12 volts to the wrong pins you are probably done with them.
Even if you could get one to work at all there is still a good chance you fried something that you may need for a project.
Not at all sure why you picked "Website and Forum" to post so i will move you to the correct section.
Could you also take a few moments to Learn How To Use The Forum.
Other general help and troubleshooting advice can be found here.
It will help you get the best out of the forum in the future.
It's toast. But on the lessons learned part- If you don't overpower the arduino and it randomly starts acting odd, go ahead and feel it. If it is hot, you cooked it either by shorting a pin you didn't notice or draw too much from too many pins. I have done both many times! They should never get that hot