My board is not detected, possible solutions

Hi, people! Newbie here, but enthusiast and eager to learn.

Sometime ago I bought an Arduino Uno R3 clone, with Atmega 328P and the famous CH340G. Uploaded some sketch and everything was working just fine. But last Wednesday my Mac doesn’t recognized anymore the board. Before I go on with the issue, let me say that I checked with:

  • MacOS 11.3. Arduino IDE 1.8.13.
  • Windows 10 on Lenovo.
  • Linux Debian on a Raspberry Pi.

None of them recognized the board. Not even from the terminal.

On Mac ioreg -p IOUSB -w0 | sed 's/[^o]*o //; s/@.*$//' | grep -v '^Root.*' doesn’t show anything.
On Linux lsusb neither.

Others peripherals where recognized (like my Kindle or my iPhone). I bought another cable, and neither worked.

After some research, I saw that the CH340G need some drivers to working. But in this case, it’s not a driver issue, since until last month everything works correctly.

Found the schematics for the exactly model that I have here: https://www.terraelectronica.ru/pdf/show?pdf_file=%2Fz%2FDatasheet%2FU%2FUNO_R3%28CH340G%29.pdf

By the way, I found the pinout of the ATmega 328P in Reddit, here: https://i.redd.it/bggdd9srui351.png

And with a multimeter I checked the communications line between the CH340G and the Atmega 328P. Specially this:

  • PIN 2 (TXD) to R8 resistor and then to ATmega’s PIN 30.
  • PIN 3 (RXD) to R9 resistor and then to ATmega’s PIN 31.

No issues with these lines.

Since when I plug the Arduino to the USB of my Mac, all leds are on, and the last code I uploaded still function (checked), the last thing I inspect are the lines UD - and UD + of the CH340G.

Always with the multimeter set to continuity, I check communication between PIN 5 and 6 and the pads of the USB B conector. Found that PIN 6 (D-) have communication, but PIN 5 (D+) haven’t.

So, my questions are:

Is this the possible the reason because my board is not recognize?

Theoretically, if I strip a wire of an old USB A conector, and solder each cable to each specific connector (PT1 for +5V, GND to any metal on board, and D+ and D- to PINS 5 and 6), it should work, right?

Thanks in advance! And, like I say, I’m newbie, so please bear with me!

Okay, here is your bear :bear:

You can try to solder a USB cable to the CH340G. I think a pcb trace near the connector might be broken by the forces on the connector. Are you very sure that there is no connection ? Can you solder a thin wire from the USB connector to pin 5 ?

Some have trouble with the CH340G chip itself and some say that the CH340G is unreliable. I had no problems with it yet.
The cheap crystal next to the CH340G might be broken if you hit the board against something.

My advice: Buy a new one. It is not worth the trouble (but it can be fun to actually fix it).

That’s what happens when you are argentinian but with Google Translate try to do your best in english writing. Lol.

The other lines are working. I mean, they communicate correctly with the resistors or capacitors according the schematics. I have continuity there. And also between the resistors and capacitors and the ATmega.

That’s exactly what I want to read. Yeah! It’s already broken in some kind, so… Just for fun I’m going to finish broke it. Or… Fix it. Who knows?

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