I, like many others, have encountered the avrdude error. However, I am not sure how to go about fixing mine after looking at numerous forums, etc.

avrdude: verification error, first mismatch at byte 0x0002
     0x74 != 0xe6
avrdude: verification error; content mismatch

I am simply trying to upload a simple sketch, but right when it seems it is about to finish, I get this error and the uploading loading bar simply never finishes...

Thanks for the help!


I had lots of issues when I first started. these are all things I tried and at least one of them stopped this problem occurring, but I haven't a clue which.

  1. Close the IDE (if you are using it and open it again)
  2. Disconnect your board, wait 10 seconds and reconnect it.
  3. Check you settings, are you using the correct board, etc.
  4. Use a different cable.
  5. Update your drivers.
  6. Update your IDE/Toolset.
  7. Use a different physical port on your PC.
  8. Load the Blink example, if that doesn't work you serious have issues.
  9. Reboot your PC.
  10. If you can, try a different PC.
  • So I have tried all of those except for 5 and 6. I have a mac so I am not sure how to update my drivers since they were automatically downloaded. – tyler a Jun 14 '16 at 11:59
  • Damn, always makes it more difficult when people have odd hardware platforms :). Does it work when you try and upload blink? – Code Gorilla Jun 14 '16 at 12:05
  • I does not, gives me the same error actually. – tyler a Jun 14 '16 at 15:33
  • Do you have a spare board? Are you communicating via a 3rd party board (a USB to TTL device?) – Code Gorilla Jun 14 '16 at 15:39
  • I do have a spare board, another Arduino Leonardo that works just fine. It is only this one that for some reason has been giving me this error. And I am not sure what to do. – tyler a Jun 15 '16 at 8:12

I have a USB socket on the PC which causes the Arduino to lose track of its COM port although apparently Ok with other USB devices. Check your COM port before and after you try uploading.

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