Attiny1624 programming fails in Ubuntu

[giusmos]

Hi all, I have an issue programming the Attiny1624 in Ubuntu Linux while it works fine in Windows 11. My setup is the following:

1. OS: Ubuntu 24.04
2. IDE: Arduino 2.3.7 linux AppImage downloaded from Arduino website
3. megaTinyCore: 2.6.12
4. Programmer: Adafruit High Voltage UPDI Friend
5. IC: ATTINY1624-SSF

In Ubuntu I can successfully program an Attiny1614 but the programming fails when I try with the attiny1624. In Windows 11, the exact same setup (same Arduino IDE version, same programmer and same megaTinyCore version) can successfully program the attiny1624.

I paste below the output from the Arduino IDE serial console while attempting to program the attiny1624 from the Ubuntu PC. Is this happening to anyone else? I would greatly appreciate if you can help me solving this issue in Ubuntu, I don't really want to have to use Windows :)

Sketch uses 1871 bytes (11%) of program storage space. Maximum is 16384 bytes.
Global variables use 149 bytes (7%) of dynamic memory, leaving 1899 bytes for local variables. Maximum is 2048 bytes.
"/home/user/.arduino15/packages/megaTinyCore/tools/python3/3.7.2-post1/python3" -u "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/prog.py"  -t uart -u /dev/ttyUSB0 -b 57600 -d attiny1624 --fuses 0:0b00000000 2:0x02 6:0x04 7:0x00 8:0x00 "-f/home/user/.cache/arduino/sketches/13870171F2DA4C1512A2C5C7DE307E65/Blink_LED.ino.hex" -a write -v
SerialUPDI
UPDI programming for Arduino using a serial adapter
Based on pymcuprog, with significant modifications
By Quentin Bolsee and Spence Konde
Version 1.3.1 - Aug 2025
Using serial port /dev/ttyUSB0 at 57600 baud.
Target: attiny1624
Set fuses: ['0:0b00000000', '2:0x02', '6:0x04', '7:0x00', '8:0x00']
Action: write
File: /home/user/.cache/arduino/sketches/13870171F2DA4C1512A2C5C7DE307E65/Blink_LED.ino.hex
pymcuprog.programmer - INFO - Setting up programming session for 'attiny1624'
pymcuprog.deviceinfo.deviceinfo - INFO - Looking for device attiny1624
pymcuprog.serialupdi.physical - INFO - Opening port '/dev/ttyUSB0' at '57600' baud
pymcuprog.serialupdi.link - INFO - STCS 08 to 0x03
pymcuprog.serialupdi.link - INFO - STCS 06 to 0x02
pymcuprog.serialupdi.link - INFO - LDCS from 0x00
pymcuprog.serialupdi.link - INFO - UPDI init OK
pymcuprog.serialupdi.link - INFO - STCS 06 to 0x02
pymcuprog.serialupdi.link - INFO - Setting UPDI clock to 4 MHz
pymcuprog.serialupdi.link - INFO - STCS 03 to 0x09
pymcuprog.serialupdi.physical - INFO - Switching to '57600' baud
pymcuprog.serialupdi.application - INFO - SIB: 'tinyAVR P:0D:1-3M2 (04.59B0D.0)'
pymcuprog.serialupdi.application - INFO - Device family ID: 'tinyAVR'
pymcuprog.serialupdi.application - INFO - NVM interface: 'P:0'
pymcuprog.serialupdi.application - INFO - Debug interface: 'D:1'
pymcuprog.serialupdi.application - INFO - PDI oscillator: '3M2'
pymcuprog.serialupdi.application - INFO - Extra info: '(04.59B0D.0)'
pymcuprog.serialupdi.application - INFO - Using 16-bit UPDI
pymcuprog.serialupdi.link - INFO - LDCS from 0x00
Traceback (most recent call last):
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/prog.py", line 289, in <module>
pymcuprog.serialupdi.physical - INFO - Closing port '/dev/ttyUSB0'
    main()
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/prog.py", line 129, in main
    return_code = pymcuprog_basic(args, fuses_dict)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/prog.py", line 200, in pymcuprog_basic
    status = pymcu._start_session(backend,
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/libs/pymcuprog/pymcuprog_main.py", line 545, in _start_session
    backend.start_session(sessionconfig)
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/libs/pymcuprog/backend.py", line 359, in start_session
    self.programmer.setup_device(
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/libs/pymcuprog/programmer.py", line 78, in setup_device
    self.device_model = get_nvm_access_provider(self.transport,
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/libs/pymcuprog/nvm.py", line 42, in get_nvm_access_provider
    accessprovider = NvmAccessProviderSerial(transport, device_info, baud=frequency, options=options)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/libs/pymcuprog/nvmserialupdi.py", line 59, in __init__
    self.avr.read_device_info()
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/libs/pymcuprog/serialupdi/application.py", line 125, in read_device_info
    self.logger.info("PDI revision = 0x%02X", self.readwrite.read_cs(constants.UPDI_CS_STATUSA) >> 4)
                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/libs/pymcuprog/serialupdi/readwrite.py", line 25, in read_cs
    return self.datalink.ldcs(address)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.arduino15/packages/megaTinyCore/hardware/megaavr/2.6.12/tools/libs/pymcuprog/serialupdi/link.py", line 87, in ldcs
    raise PymcuprogError("Unexpected number of bytes in response: "
pymcuprog.pymcuprog_errors.PymcuprogError: Unexpected number of bytes in response: 0 byte(s) expected 1 byte(s)
Failed programming: uploading error: exit status 1

[giusmos]

@SpenceKonde, have you experienced this issue with the Attiny1624 or any other 2-series variant on linux? Do you have any suggestions on what to try to make this work also in linux? Maybe the linux drivers of the CH340E chip are not good enough and I need to use another USB to serial IC? If yes, which one?

[giusmos]

I have now tested using a cheap CP2102 USB-to-UART adapter from Aliexpress, I just added a 1k Ohm resistor between RX and TX pin and connected the RX pin to the UPDI port of the attiny1624. This works fine as I can successfully program the MCU from Ubuntu Linux.

The Adafruit HV UPDI Friend works on Linux with the attiny1614 but not with the attiny1624, while it works with both on Windows 11.

I think this shows that the CH340 drivers do not work well with the 2-series attiny in Linux. I wonder why.