Got two fried Arduino, any advice? Rx Tx Blinking together

I have two arduino, i dont know if they are really fried, both have blinking RS TX together after usb connection. Is there any way to fix? Someone has the same problem?

Which Arduino's?

Have you tried the "serial loopback test", see if the USB/Serial chip is still working?

Actually i dont know what this means:

  1. Connect the terminal application to the serial port for your board. The baud rate is irrelevant.

Wich is the serial port? How shoul i connect the serial port?

My arduino is nano.

Your Nano uses USB as serial port like most arduinos.

It may be possible other devices are also connected and behave like serial ports, selecting the right one is important. Easiest is probably disconnecting the nano first, starting the arduino software on your PC and clicking Tools -> Serial port.

Remember which Com:-ports are already showing ( if any) and after that repeat these steps with... your Nano connected to the PC. If the USB-chip is still talking to the PC there should be another COM-device added to the list of serial ports.

If it shows you'll need to select that specific serial-port in Tools -> Serial port and continue the test with jumpers on the right places. If it doesn't show the USB-chip on the bottom-side of the Nano isn't communicating with the PC.

The other COM is not showing, but the pc emitts plugghed sound device. So what is fried?

I guess (!) the FT232-chip (bottom nano) which takes care of communication with the PC has a problem/may be fried, but I'm not sure.

Hearing a sound might indicate the PC still detects something is plugged in, but that it can't detect what. If the chip is fried it still is a question what the condition is of the other components on the Nano.

I must say I don't know whether not seeing the right com-port automatically means the chip is fried, I would expect most USB-cables to act as they should, but changing a cable to see what happens doesn't hurt.

Ditto for checking device management of your PC, If the PC makes the sound it detects something... and hopefully a device shows up in the device management-list. Re-installing the USB-driver for the chip http://www.ftdichip.com/Drivers/VCP.htm would be the next step in case software on your PC causes problems. If both Nanos stopped functioning at the same time that could be the case.

I'm far from an expert, should these steps give no results, I think it's strange that the leds are still blinking. I would expect 'm to be on or off, not blinking. Whether a working sketch on the microcontroller might still be able to trigger the leds to blink on a (perhaps) partly fried chip, or that a partly fried chip might still blink as it normally also does when it's connected, I don't know.

USB-communication is quite delicate/difficult, the USB-chip itself can also be configured, it has its own EEPPROM. I would not expect chips to change configuration though. On http://www.ftdichip.com/Support/Utilities.htm you can find several utilities to look at/change settings, FT_prog might... give you some info if the chip still functions.

I must say I.... never used/needed these utilities, I just discovered 'm today. According to the warnings on the site you might ruin a good chip if you configure it wrong using these utils. Should the chip still give some info I'd be very sure to know what I'd change before doing so.

Thank you really much for your explanation :)