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[on:]

After setup my project and loading my first sketch on a brand new Arduino Leonardo, the board doesn't connect with PC anymore. Plugging USB connection now I see at first "Arduino Leonardo" on COM9 (like the first time) but then it disappear from COM ports (while at first it switched on COM8 and it remained there).
I have to resign to a permanent damaged board or I could attempt something ? Connections (image attached) I made could have burn the board ?
Thanks
alberto

[Reply #1 on:]

Have you checked for short circuits? Disconnect everything and connecting it to the PC again.

[Reply #2 on:]

Thank you for advice Shpaget, but the board, now completely disconnected, doesn't connect.

[Reply #3 on:]

Suggest power down and restart the PC (and of course the Arduino) and start from a clean state.

Can you now see and select the Arduino's COM port in the IDE? If so, try uploading any of the example sketches (ensure the correct board type is selected first).

[Reply #4 on:]

I did all of these. Reboot PC , unplug Arduino board, disconnect all wires from board, then re-plug USB connection and PC shows for a second an Arduino Leonardo on COM9 but immediately disappear (instead of automatically pass on COM8 port like before) .
No COM8 (or COM9) port in Arduino IDE neither in Windows Device Manager so I cannot load any sketches (or bootloader) on board. Board in Arduino IDE is correctly selected

thanks for support

[Reply #5 on:]

I don't know what drivers come with the Leonardo board, but the ordinary Arduino board uses drivers for the FTDI chip.

Try to find out which drivers the Leonardo board uses and reinstall them.

[Reply #6 on:]

I understand you all suppose this is a driver issue but nothing worked until now. Uninstall drivers (during those the few second it appear on COM9) , then poweroff PC , poweron, then plugin USB and reinstalling drivers. Trying on different USB port. Always the same behaviour, a few second I can see Arduino Leaonardo on COM9 then it disappears.

Thank you all

[Reply #7 on:]

OK. Solved !  
I wrote a new sketch simple as possible. then I pushed upload button and immediately I made a board reset. (During these few seconds it is connected on port9, I suppose) Arduino IDE was be able to upload that sketch to the board. After that I made a new reset of the board and the COM association is come back normal (few seconds on COM9 and then keep up on COM8) and the new sketch work fine (I can see messages on port monitor).
So I can tell you the problem is in my original sketch that, in some way break the connection.

Thank you all guys again for support
Alberto

[Reply #8 on:]

OK. Solved !  
I wrote a new sketch simple as possible. then I pushed upload button and immediately I made a board reset. (During these few seconds it is connected on port9, I suppose) Arduino IDE was be able to upload that sketch to the board. After that I made a new reset of the board and the COM association is came back normal (few seconds on COM9 and then keep up on COM8) and the new sketch work fine (I can see messages on port monitor).
So I can tell you the problem is in my original sketch that, in some way break the connection.

Thank you all guys again for support
Alberto

The ATmega32U4 used in the Leonardo includes USB, so it can be "stuck" in a seemingly damaged way.  The Teensy 2.0 (that also uses the ATmega32U4) is a little more robust with problems like this.  But, it seems you've figured out what you need to do.  This won't be the last time either, it happens often.  I also have problems when doing ultra-low powered sketches that turn off the USB interface.  Kind of hard to upload to the CPU if the sketch turns off the USB.  You may want to avoid doing this with an Leonardo till you're a little more experienced.

Another good tip is to add a 2 second delay at the start of your sketch when doing something that could get you stuck.  That should give you enough time to make sure you don't end up in bad situation.

Tim