UPDI fails to initialise

Hi,

Using pymcuprog to program an AVR4809 with the following command line:

pymcuprog write -d atmega4809 -t uart -u COM3 -c 250k -f .pio\build\ATmega4809\firmware.hex —erase

I get the following error:

ERROR - Operation failed with PymcuprogError: UPDI initialisation failed

I have a 1k resistor connected across the tx and rx pins of an FTDI chip as per the pyupdi diagram here. I use it a lot with other 4809 projects.

Is there anything I can try to resolve this?
thanks.

I just tried a different command line:

pymcuprog write -d atmega4809 -t uart -u COM6 -c 115k -f .pio\build\ATmega4809\firmware.hex --erase

which just changed -c 250k to -c115k and the upload works:

pymcuprog write -d atmega4809 -t uart -u COM6 -c 115k -f .pio\build\ATmega4809\firmware.hex --erase
Connecting to SerialUPDI
Pinging device...
Ping response: 1E9651
Erasing device before writing from hex file...
Writing from hex file...
Writing flash...
Done.

But the blinkled code doesn’t work …
I’ll use my Arduino Uno programmer to check…

yes my Led on pin 23 blinks if I upload the same code via the arduino IDE and jtag2updi Uno programmer.

Any help to get Pymcuprog sorted would be much appreciated.