[SOLVED] Strange connection issue with Arduino Leonardo

I just got a new Arduino Leonardo board yesterday and it worked flawlessly after i first plugged it in to my notebook. I also uploaded some programs and tested with some devices on the breadboard. No sign of error was found at that time.
But after i unplugged it and moved to another notebook this morning. The Arduino Leonardo entry does appear in the device manager for a while between the L led has been blinking then the entry became hidden from the list. Pushing the reset button gives the same result as re-plugging the cable.
I thought it was the voltage problem. So, i put the 9v external power to the board and nothing changed.

After forcing the device manager to show all items, I’ve found my device with the lighter color of icon (as in the attached picture). By entering the properties menu, it said “Currently, this hardware device is not connected to the computer. (Code 45)” while my cable is already connected and the green led is turned on steadily.

Also found a guy that’s facing the same problem with me here Atmega32u4 de-registeres itself -Freetronics Forum . Surely no answer for him yet :confused:

Any suggestion ?


Try moving to another USB port. Also, if you have a USB Hub it can help. I think this is more an operating system issue.

spcomputing: Try moving to another USB port. Also, if you have a USB Hub it can help. I think this is more an operating system issue.

Using all ports of 2 notebooks, both are running Windows 7 with x64 and x32. There's no difference. I'll update the result after trying the Hub. Thanks for reply :)

I have a Leonardo coming in tomorrow, but it should behave like my other Unos and Megas. I have 4 laptops to torture with it...

Finally I figured it out. Not sure if there was a conflict in the last time i unplugged after uploading or not. - -a But i fixed the port in preferences.txt to the same port as the pale icon in my first picture then uploaded the new sketch at the moment that the Leonardo's entry appears in the device manager (this happened for 2 - 3 seconds after pressing reset button as i said) and it works. The OS recognized it as new device and gave it new port number.

Hope this information helps when your device arrives. Anyway, more hope for no problem at all :)

Wow. That is one grumpy Arduino... With that connecting and disconnecting (CDC/VCOM) no wonder the USB got confused. When mine "hangs" during upload for more than 8 seconds, a simple hit to the reset button seems to recover it and upload commences.

Fading "D13" is kinda fun. Has anyone got the Serial to come out of serial monitor while a sketch is running? I tried the while(!serial) hack to no avail.