Arduino Mega sold with faulty CH340G interface

Community General Discussion
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I just acquired an Arduino Mega. It's a made in China version with a CH340G USB to serial interface.

After a brief diagnostic I came to the conclusion that it has been sold to me faulty.

  • Burn bootloader from external programmer... OK
  • Upload sketch using tx/rx on DIO pins... OK
  • Upload sketch using USB interface... FAIL

Clearly something is wrong with the USB-serial interface.
We have been using the CH340G with other devices maybe around ten thousand times and do this every day. So driver issues are not the case here.

Before I savage the card by trying to replace the 12mhz crystal and/or the CH340 itself has anyone been confronted to the same problem? If so did you find a hardware fix for it?

(I liaising with whoever sold this to me as well of course).

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Yes, I have had the same problem.

My hardware solution is to buy at least two and hope that at least one works and throw the bad one in the trash. Overall, it's still cheaper than buying one of the official Arduino Megas.

They crank out those boards by the thousands/month (maybe more). The micro is pre-programmed with blinky, so if the LED blinks, I guess they consider the whole board to be good.

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Right - Buy trash and don't support The Project.
Brilliant!

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I'm sure that the original Arduino team knew what they were doing when they decided to make it open source hardware.

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Just send it back. If the seller won't exchange it, support a more responsible seller.

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Did you try manually resetting the mega when the upload starts, to see if it was a problem with the auto reset circuit?

Have you tried a sketch to send text out Serial to see if it shows up in the serial monitor?

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I think you should contact the seller ASAP. If the board is still under warranty, they must provide a replacement.

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the manual reset gets nowhere. Good thinking though. Thanks.

Monitoring the serial output using a FTDI232 adaptor connected on tx/rx DIO works really solid (as expected).

On the USB interface however I get the first second of output then nothing (just using a sketch that output every seconds). Somehow the CH340 can not cope.
Probably not an issue with the crystal then otherwise it would not work at all.

Yes I am in contact with the seller. However if I find a quick way to fix it that would do me as I can't be bothered waiting another week to get a new board and work on the project.
When you buy cheap... you get cheap. I know.

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most likely it's just bad soldering, a fairly common occurrence on Chinese boards

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