Cannot select serial port for Mega2560 in GUI

I have received my Mega2560 but cannot upload a sketch. The Arduino GUI does not let me select the serial port, it is greyed out.

I have arduino version 21 installed on a Debian squeeze system. The arduino shows up as /dev/ttyACM0.

This is what I have atready done:

in ~./.arduino/preferences.txt serial.port=/dev/ttyACM0

checked permissions: my user is in the dialout group which has r/w permissions on the device. echo "something" > /dev/ttyACM0 lets the RX led on the board blink.

Still no luck with the GUI.


Take a look at the following thread, they might be something for you :

Troubleshooting ? No ttyUSB0 in arduino IDE Ubuntu

Check also the kernel version you are using : uname -a

On the thread above, somebody mentioned a fix should be included in kernel "2.6.37.x"

Thanks a lot kilotron.

I have studied the thread you gave, but it did not help. I do not really think it is the same problem, as ttyUSB0 works fine here (with older Arduino boards) but devACM0 does not (mega2560). I have invested so many hours to find a solution, but still have no clue.

Could it be a hardware problem? (keep in mind that ´echo "something" > /dev/ttyACM0´ does show activity on the Arduinos RX led).

Any suggestions very much appreciated.

btw, I´d rather stay on Debian squeeze kernel, as I do a lot of testing squeeze on this machine. 2.6.32-5-686. If I´d really get the impression that it would be a kernel bug I´m not afraid of applying patches and compiling kernels though. I only would run into hd space problems right now... But I do not think it is the kernel bug mentioned in the other thread.

I´d rather stay on Debian squeeze kernel

I agree with you, I just did not know what you were using.

Do you have a lot of hardware connected to the computer’s USB ports ?
(mouse, scanner,…)

What is connected to your Arduino board ?
(sensor, motors…)

How do you power your board ?
(from the USB port, external power supply)

If connected to the USB port only (no external power supply), try a test.
Connect the minimum amount of hardware to the board and try the upload one more time.

kilotron, I had already tried most of your suggestions before, and did check adding an external power supply to the (empty) Mega2560 board now, but still no luck :(

I have managed to find a Windows XP machine to try there (Arduino v21). On this installation I can select the serial port. Trying to upload hangs after compiling the blink example.

After a reboot (well, it´s windows) I tried SHIFT+Upload and get: avrdude: stk500_2_ReceiveMessage(): timeout

I have also tried to press reset on the arduino before uploading.

I finally have it running!

I have purged all arduino related software from the system and renamed ~./.arduino Then I downloaded the tarfile from, untared it and re-installed the dependencies. Seems to work fine now :)

The strange thing is, that I already had tried this before and it did not help the first time. I can´t remember what I did different last time. Then there is the thing with the avrdude timeout on windows. I do not use windows, so I don´t care too much, but there might be a hidden bug in the software or my board is somehow strange.