Strange issue while flashing

Hi,

I developed a board based on an Arduino Nano (Atmega328P) where I use an external FTDI adapter to flash it.

I have both boards in breadboard and produced in PCB and flashing always worked fine.

Now when I made consecutive flashes on both (breadboard or PCB) I get immediately all 10 programming failures in a row without any waiting delay for the next retry:

avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00 avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0xe0 avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0xe0 avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0xe0 avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0xe0 avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0xe0 avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x00 avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0xe0 avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0xe0 avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0xe0

If I wait a few seconds (like 15 to 20 seconds) I can flash the board again.

Is this a software bug or feature? Or a error in my hardware? The strange thing is that this issue never occurred before.

This issue does not happen if I use an Arduino Nano. I can reflash it immediately after finishing a flash.

Any ideas?

Thanks

Vasco

Solved!

The reset diode and resistor were placed wrong when I reassembled the breadboard.

The produced PCB was experiencing the same problem because I was not aware that I was using an older hardware revision.