Help With My Arduino Mega Build

Using Arduino Microcontrollers
1

Hi
I have made a Arduino Mega schematic for my project, according to the 'Arduino Mega' Schematic on Arduino.cc, Revision 3.
I printed a test batch of the boards to test everything but I cannot connect using my usb.
Simply put, I plug in the usb, the pc does not register anything and the ATMEGA16U2 (USB Chip) just gets hot.
Not able to upload anything or even open the serial monitor as a COM Port does not open for the board.

Can anyone look over my schematic and tell me if they see anything wrong with it?
Schematic_EMS_LVL3_CONTROLLER_2022-04-06 (1).pdf (207.7 KB)

2

A standard ATmega16U2 comes with no firmware on it. Did you program it before connecting to USB? As your schematics doesn't show an ICSP header for that chip I assume you forgot that.

How hot does it get?

3

That's not good. It suggests either a major design flaw or an assembly defect. Time to whip out the multimeter and probe all voltages around that 16U2 chip and see what's up.
If you're lucky it's not yet fried. I wouldn't bet any money on it though...

4

I see now that the ATMEGA16U2 has a header, I missed that the first time. I will add that.
And I would say quite hot to the touch, something is definitely not right there.

5

It could be when i applied solder paste, I may have put to much and thus something is shorting under the chip, however, this is still the prototype phase and i have a few chips to spare.

6

Is this a QFN part or does it have leads? In any case, usually you can clean up the excess with solder wick. It also helps to have a hot air smd soldering station at hand.

I don't think this is your issue though.

7

It is the 16U2-MU so the connections are at the bottom of the part.
When i first applied solder paste, i applied way to much, and i had to remove the excess around the outside of the part with solder wick, but i cannot see under the part.
Quick question, if the 16U2-MU does not have firmware on, will my pc still pick it up in the usb port?
Also i can send my board design but everything is connected as per the arduino schematic as far as i can tell

8

Don't think so, no.

9

So the only way i can test it is to connect it and just make sure its not getting hot?
For now at least

10

Yeah, pretty much so.

11

Umm one more question, do you perhaps know what the jumpers are used for? And should i leave them open or close them up on my design?

12

Errr....this is your design isn't it...

13

Yes, but I mean in the Arduino schematic on Arduino.cc there are a few 'jumpers' in the schematic that i read were just open solder pads, but what are their function when it comes to the functionality of the Arduino?

14

Using the GND pads you can connect the USB GND to the system GND or separate them.
Using the RESET pads you can cut the trace that connects always and then have a solder bridge that defines if a DTR signal resets the main processor or not (given you use the Arduino firmware for the ATmega16U2).
Have you found more?

15

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