I have a problem again with an Arduino Mega 2560 board (SainSmart). The IDE gets stuck at the "Uploading to I/O board..." message. The bargraph shows around 95% but then there is no further progress. I tried this with Windows 7 64bit and Win XP, with 101 and 0023. Uploading is impossible. Board type and COM port are correctly set in the IDE. Any ideas to solve the problem?

  • \$\begingroup\$ Is there any error message or does it just hang? If it hangs does it have an info bar saying at what stage? \$\endgroup\$
    – Oli Glaser
    Jul 16, 2012 at 3:53
  • 1
    \$\begingroup\$ Did you try verbose mode? Turn on verbose mode in preferences(1.0) or hold shift(0022) \$\endgroup\$
    – jippie
    Jul 17, 2012 at 21:32

1 Answer 1


Do you have another Mega board to test with? That way we can tell if it's just this specific board. Is it timing out? Something like...

avrdude: stk500_2_ReceiveMessage(): timeout

It could very well be a driver issue. Give this a go:


1) Go to System Preferences -> Network

2) If it asks you to add the Arduino (modem device), say cancel

3) Remove the Arduino device from the list if its there

4) Try uploading a sketch!


1) Go to Device Manager

2) Find your Arduino in the list, go to its properties and update its driver manually, using the .inf file which came with your Arduino (0021+) IDE

Also, make sure you're not sending !!! via serial at any point in your sketch as that initiates a special monitoring mode baked into the bootloader.


Also, take a look at the official Arduino troubleshooting guide.


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