Hi, guys, I am quite new to playing with Arduino. I have two Arduino, one of which is from ELEGOO. Yesterday I was doing some testing, and everything seemed okay, at least all connections were working properly. I then pressed the side reset button to reset the board to re-upload new codes. Thereafter, I can no longer find the port to the ELEGOO UNO, on top of it, when I plug the USB into its port, the bottom of the port begins to heat up. While the Arduino Uno one was doing fine (I also reset the Arduino Uno board by pressing the side button). In the first picture, I have circled out the heating area. The second picture shows the error when I connected the ELEGOO UNO. The third picture shows the correct port (the 2nd one) when I connect the Arduino UNO. The ports in the second picture are selected by me, and not automatically detected by the Arduino board. I wonder what the problem was, is there anyone who encountered the same situation and fixed it? Thank you guys very much!
On the other side of such area there's the serial interface chip (ATmega16U2), so I'm sorry to say I think something went wrong with it. For example, if when prototyping you don't have a clean table any small conductive item (like cutted wires) could damage your circuit, maybe .
Anyway, have a look at the top of the Uno around that area and search for any type of anomaly. Try also to wipe all the surface off using a small soft brush, then connect the USB cable and see what happens.
But if it was a temporary short circuit (e.g. something under the Uno when you pressed the reset button) damaging the chip, you won't be able to see any visible change, and you can't do anything more than that.
Hi, @wenxuanxiss
Welcome to the forum.
You don't have to do that, just keep uploading when you need to.
RESET doesn't erase your code, and the bootloader takes care of the programming.
Can you post a schematic and/or images of your project, showing ALL the devices you had connected to the UNO when this occurred?
Thanks.. Tom.. 
Indeed, I think I have fried the communication chip and I also do not think there is anything I can do. But thanks still for your answer.
Hi, Tom, thanks for your suggestion, but I am afraid that I have fired the communication chip. I went to a local maker space and had some of the teachers checked for me, they confirmed that I had successfully fried my first Arduino. https://www.youtube.com/watch?v=RfrDtAEQ95c, this is the tutorial I followed. But instead of having a Mosfet, I used a bipolar transistor, and I made the exact connection without noticing the pins on the Mosfet and the bipolar transistor were different.
Good move, you also need to check the base series resistor value when going from MOSFET to BJT.
Tom..
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