Hi, I have started to have an intermittent problem which has now become persistent, and I can’t upload code to my AVR4809. There are two separate 4809s in a project box with separate FTDIs. Each is on its own breadboard. The one uploads fine, the one with the fault now will not upload code and I get this pymcuprog error:
PS C:\Users\Paul\Documents\PlatformIO\Projects\Live\Stepper> pymcuprog write -d atmega4809 -t uart -u COM17 -c 250k -f .pio\build\ATmega4809\firmware.hex
pymcuprog.serialupdi.link - WARNING - Check failed
pymcuprog.serialupdi.link - WARNING - Check failed
Traceback (most recent call last):
File "c:\users\paul\appdata\local\programs\python\python39\lib\runpy.py", line 197, in _run_module_as_main
return _run_code(code, main_globals, None,
File "c:\users\paul\appdata\local\programs\python\python39\lib\runpy.py", line 87, in _run_code
exec(code, run_globals)
File "C:\Users\Paul\AppData\Local\Programs\Python\Python39\Scripts\pymcuprog.exe\__main__.py", line 7, in <module>
File "c:\users\paul\appdata\local\programs\python\python39\lib\site-packages\pymcuprog\pymcuprog.py", line 285, in main
return pymcuprog_main.pymcuprog(arguments)
File "c:\users\paul\appdata\local\programs\python\python39\lib\site-packages\pymcuprog\pymcuprog_main.py", line 80, in pymcuprog
status = _start_session(backend, device_selected, args)
File "c:\users\paul\appdata\local\programs\python\python39\lib\site-packages\pymcuprog\pymcuprog_main.py", line 549, in _start_session
backend.start_session(sessionconfig)
File "c:\users\paul\appdata\local\programs\python\python39\lib\site-packages\pymcuprog\backend.py", line 363, in start_session
self.programmer.setup_device(
File "c:\users\paul\appdata\local\programs\python\python39\lib\site-packages\pymcuprog\programmer.py", line 78, in setup_device
self.device_model = get_nvm_access_provider(self.transport,
File "c:\users\paul\appdata\local\programs\python\python39\lib\site-packages\pymcuprog\nvm.py", line 44, in get_nvm_access_provider
accessprovider = NvmAccessProviderSerial(transport, device_info, baud=frequency, options=options)
File "c:\users\paul\appdata\local\programs\python\python39\lib\site-packages\pymcuprog\nvmserialupdi.py", line 51, in __init__
self.avr = UpdiApplication(port, baud, self.dut)
File "c:\users\paul\appdata\local\programs\python\python39\lib\site-packages\pymcuprog\serialupdi\application.py", line 81, in __init__
datalink.init_datalink()
File "c:\users\paul\appdata\local\programs\python\python39\lib\site-packages\pymcuprog\serialupdi\link.py", line 60, in init_datalink
raise PymcuprogError("UPDI initialisation failed")
pymcuprog.pymcuprog_errors.PymcuprogError: UPDI initialisation failed
the pymcuprog command i use for code uploads on the two AVRs is identical:
pymcuprog write -d atmega4809 -t uart -u COM17 -c 250k -f .pio\build\ATmega4809\firmware.hex
So I am hoping someone might have an idea what the problem is. Here’s the things I’ve tried
Checked all the connections on the breadboard
rechecked particularly the UPDI wiring several times
Reseated the 4809 in its zif connector
Reseated the zif in the breadboard (it’s back in EXACTLY the same place btw 
)
Checked VCC at the avr4809 VCC pin which is 5.5V (power is derived from the FTDI chip)
Replaced the 1k resistor between the Tx and Rx lnes as per PyUPDI
changed the -c parameter in the pymcuprog command to -c 115200
Restarted the USB hub
Changed the USB cable
Changed the FTDI chip
Is there any thing else I could do before swapping out the AVR4809?
any ideas much appreciated.
I guess it’s worth adding that I know the connections are correct because every now and again, the code will upload - I get a success message, but the code doesn’t seem to run, I have no serial comms for instance via the serial monitor (the code has been tested extensively). I was hoping to upload a blinkled program, but can’t upload at all now.