Rapid flashing of L LED -- upload fails

I am using the 0021 IDE with a mature/working Duemilanouve board…

This post relates to the L (Pin 13) LED rapid flash syndrome. It appears to be common and there are several posts about this over an 18 month period. During the fast flash time, uploads are aborted. The LED flash starts about 7 seconds after poweron.

I tried uploading a simple “Hello LED” sketch DURING the short period after power on and before the LED goes into a 10Hz flash mode. This worked and at least temporally fixed the problem. Others have suggested this trick.

I could then upload complex sketches w/o problem. Then the “fast blink LED” problem returned! This is a pain and seems no one has really found the source of the issue.

FYI after the upload times out I get this error message;

avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51

Any suggestions…

Thanks! Al

Any suggestions.

I would suggest that this statement:-

with a mature/working Duemilanouve board.

is not true and that the auto reset circuit is gone. Try a manual reset, hold down the reset button, click the download icon, when the message showing the sketch appears count to two and release the reset button.

I have tried lots of manual reset maneuvers. I can get it to download if I upload immediately after poweron. Then I can download other sketches until it hangs again. My comment about "mature/working" was meant to imply that the board had worked fine until this odd problem took hold.

Your idea about the auto reset being faulty may be the case. I may need to replace the card. The Mega2560 has a HW reset chip. I am not sure how the Duemilanouve is reset...


I am not sure how the Duemilanouve is reset...

It uses the DTR line from the serial port through a capacitor.

I can get it to download if I upload immediately after poweron

If you can do this but not get it to download with the manual reset button it sounds like you have a bad joint between the button and the reset pin on the processor.

The manual reset button works fine. The problem happens on poweron. I suspect there is some odd problem that may be related to hardware, unclear. I do wonder if there is some corruption of the bootloader that may cause the problem. Thanks for the help...

I am not sure if these two statements from you stack up:-

I can get it to download if I upload immediately after poweron.


The problem happens on poweron

You have me confused as to what you are seeing. :-/

Well, on poweron the LED L goes into 10hz flash mode after about 5 seconds. Hitting the reset button during this time does not prevent the LED flash sequence from starting.

Now, if I quickly do a small upload during the 5 free seconds, I can usually get the sketch to run. Others on this forum have been able to upload "Hello LED" during this time too. Then if I upload another sketch (more complex) the LED L flash sometimes returns..

My plan is to wait for the Mega2560 and associated software to stabilize then jump to it. Thanks again.

Are your programs using the serial connection to the computer a lot? I had this happen to me once and used the ol' "hold reset, upload sketch, release reset at just the right time" trick to fix it but it took 4 hours of research to figure out that was the fix.

Then I was working on my project some more and was having trouble. After another hour of research I found out pins 0 and 1 are used for serial communication which I did not know.

Then I just read this thread and it seems to me it might be that if you try to upload a sketch at the same time serial communication is going on it could cause a problem.

I am not using the serial connection -- just the USB port connected to my PC. I have used this same configuration many times and only recently has the "flashing LED L" syndrome been an issue. Something has changed and I will assume for now that it is HW related.