Arduino FTDI upload works only once, then locks up

This is puzzling.

Having upload problems with a formerly reliable set-up for months, using BBB & RBBB atmega168 arduino-clones, several of each.

I'm uploading via COM3 FTDI with latest drivers. Windows 7.

Sketch upload via Arduino-0018 works ONCE via the FTDI, then produces

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

on each additonal try.

The only 'new' changes to my setup: Having downloaded WinAVR and AVRstudio, I thought perhaps it was multiple copies of avrdude. I've since removed all but the one in Arduino-0018. Also removed and reinstalled Arduino-0018. Removed and reinstalled all com ports. Tried reinstalling bootloaders on the Arduinos. Tried an upload via COM1 using a P4 serial upload form moderndevices, THAT works reliably with multiple uploads. Tried COM1 ports both higher and lower than COM3 Removed all other programs that could conceivably deal with the COM ports. Checked task manager to see what else was running. Tried fresh drivers directly from FTDI even though Win7 said I had the latest. Rebooted between each of the above steps.

My gut tells me for some reason the FTDI is not 'releasing' COM3, since it will work once each time the COM port is reinstalled.

Any suggestions on what else I can try? Uploading via the FTDI is more convenient than the P4 serial cable.


I have always had this problem when using an ftdi cable, upload once then zilch/nothing. I have to press the reset button to upload or unplug/replug the cable and start again.

I also have a Sparkfun usb/ttl breakout board which works perfectly every time so it seems that my problem is with the ftdi cable.

Glad to see I’m not going crazy! It’s not fundamental to a working cable. Something must be horked on our set-ups, and on mine, recently. I was able to repeatably upload via FTDI for two years of Arduino development.

In addition to the above, I’ve experimented with changing the COM port speed from 9600 all the way to 38400. I’ve also removed WinAVR and AVRstudio.

Getting close to a Win7 reinstall! Hope I don’t need to go there.

“reseting” between uploads doesn’t seem to help, in my case, although it seems to helped in yours.


Well, that was good for a whole day of debugging.

Not sure which of the dozens thing I did 'lead' to a fix, but I can help others with the last thing I did before it started working reliably again.

I reburned my atmega168(s) with the vanilla bootloaders from the Arduino hardware directory.

I set the COM port speed up to 115k

I set the the RTS on close flag in the 'advanced' COM port settings for the COM port corresponding to the FTDI cable.

About 90% sure it was this last item - I can reliably have it lock up on the 2nd upload when this flag is unset, and then reliably fix it when it when this box is checked.

I still have no theory why I've never needed to set this before for reliable operation or perhaps something unset it after myriad installs/removals of other software.