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Topic: Arduino Uno RX and TX lines not working/flashing when board is plugged into PC (Read 1 time) previous topic - next topic


Hello fellow Arduino users,

after playing around with a few test sketches for arduino with the Leonardo board, I changed to the Uno r3 board so I can use the Leonardo for other tasks.

Upon plugging the Genuino Uno R3 into the working USB port (provenly works with Arduinos, just not with my Uno) the power LED and the pin13 LED lit up, however the RX and TX LEDs did not.
Usually when I plug in my Arduino boards the RX LED flashes once or twice, but that doesn't happen anymore.

I can communicate with my Leonardo board which I can find in the tool options, however I can not communicate with the Uno board which simply doesn't show up in the serial port menu.

Did anyone ever have this problem before? What can I do to fix it?

Thanks to everyone in advance for taking time to answer my question.

Important Informations:

Affected board: Genuino Uno R3
No software updates were made and also no short circuits occured while playing around with it, from one day to another it stopped communicating.

The USB cable is not broken, all 4 lines (pwr, gnd, D+, D-) are connected in the proper order and are not broken, I doublechecked with a second USB Type-B cable

The USB port on my laptop is working with arduino as well, the Leonardo has no problems communicating with either USB ports, the RX LED flashes upon plugging the Leonardo in, but not with the Uno.

I can not see any visibly damaged or fried components, when I plug it into 9V DC or connect it to a powerbank/PC the power LED lights up, the pin13 LED lights up and no components get hot after being plugged in for several minutes.


Any unknown devices in device manager?

Which serial adapter does it use? Ch340g drivers aren't included with the ide sincenits only used in clones (but they work great), so you'll have to download those if you don't have that installed already. FT232 can be fake (google ftdigate) and the fakesndont work anymore. And the 16u2 used on the official boards seems to be fairly prone to failure from electrical abuse.

I don't recall seeing tx/rx flash on plugging board in on non-native usb avr boards (havent played with micro / Leo boards)
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I'm using a MacBook with OS X El Capitan to code it, I never changed anything and I'm 100% positive that it'll have to do with the board itself.

The chip close to the USB port of the Uno is an ATMEL Mega16u2

In that case it seems that this chip is broken and I guess I'd be better off buying a new arduino rather than ordering a new Mega16u2 and fiddling around with soldering it on.

Do you think that this might be the reason why it's not working?

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