avrdude: usbdev_open(): cannot open device: Permission denied

Question

I'm trying to upload anything to my Arduino Uno Wifi Rev2, I'm on Arch Linux, but I'm failing with the following error be it via IDEv2 or arduino-cli:

avrdude: usbdev_open(): cannot open device: Permission denied

avrdude: jtag3_open_common(): Did not find any device matching VID 0x03eb and PID list: 0x2145

The device permissions:

crw-rw-rw- 166,0 root uucp 9 Jan 23:22 /dev/ttyACM0

My udev rule:

KERNEL=="ttyACM[0-9]",MODE="0666",GROUP="uucp",TAG+="uaccess"

lsusb:

Bus 001 Device 005: ID 03eb:2145 Atmel Corp. ATMEGA328P-XMINI (CDC ACM)

First two entries from udevadm info -a -n /dev/ttyACM0:

 looking at device '/devices/pci0000:00/0000:00:14.0/usb1/1-3/1-3:1.1/tty/ttyACM0':
 KERNEL=="ttyACM0"
 SUBSYSTEM=="tty"
 DRIVER==""
 ATTR{power/control}=="auto"
 ATTR{power/runtime_active_time}=="0"
 ATTR{power/runtime_status}=="unsupported"
 ATTR{power/runtime_suspended_time}=="0"
 looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1/1-3/1-3:1.1':
 KERNELS=="1-3:1.1"
 SUBSYSTEMS=="usb"
 DRIVERS=="cdc_acm"
 ATTRS{authorized}=="1"
 ATTRS{bAlternateSetting}==" 0"
 ATTRS{bInterfaceClass}=="02"
 ATTRS{bInterfaceNumber}=="01"
 ATTRS{bInterfaceProtocol}=="01"
 ATTRS{bInterfaceSubClass}=="02"
 ATTRS{bNumEndpoints}=="01"
 ATTRS{bmCapabilities}=="6"
 ATTRS{iad_bFirstInterface}=="01"
 ATTRS{iad_bFunctionClass}=="02"
 ATTRS{iad_bFunctionProtocol}=="01"
 ATTRS{iad_bFunctionSubClass}=="02"
 ATTRS{iad_bInterfaceCount}=="02"
 ATTRS{physical_location/dock}=="no"
 ATTRS{physical_location/horizontal_position}=="left"
 ATTRS{physical_location/lid}=="no"
 ATTRS{physical_location/panel}=="top"
 ATTRS{physical_location/vertical_position}=="upper"
 ATTRS{supports_autosuspend}=="1"

I feel like I've tried everything so far:

• sudo chmod a+rw /dev/ttyACM0
• sudo usermod -a -G uucp $USER
• adding udev rule with all different configs (although if chown/chmod doesn't work what will it change??)
• changing ownership to my user...
• I checked the process for the IDE to make sure it runs on my user and it does
• After all these steps I always either restarted and/or reloaded everything with sudo udevadm control --reload-rules && sudo udevadm trigger
• Went through plethora of similar topics, no clues

I feel like I must be doing something awfully stupid here, it doesn't make any sense to me why it wouldn't work even after I chown'ed it to my user...

Answer 1

Looking at the board definition for the UNO WIFI R2, it doesn't use the serial port for upload. It's using an mdbg chip that it speaks to over a non-cdcacm USB protocol. Getting yourself into the group-owner for the serial device is good for communicating to the board through the serial monitor though.

The megaavr board package seems to come with a file for creating your udev rules that you should find at:

"${USER}/.arduino15/packages/arduino/hardware/megaavr/1.8.8/scripts/create_dfu_udev_rule"

The 1.8.8 subdirectory of megaavr is current as of writing. It will no doubt change. I still have 1.8.7 on my system.

Running it should create the necessary udev rule for allowing avrdude to speak directly to the USB device. Specifically they're adding this:

SUBSYSTEM=="usb", ATTR{idVendor}=="03eb", ATTR{idProduct}=="2145", MODE="0666", ENV{ID_MM_DEVICE_IGNORE}="1"

They seem to be creating a udev rule for the tty device as well, though that shouldn't strictly be necessary given what you've already done with becoming a member of the serial device's group. Basically you're doing it by becoming a member of the owning group where what they did was just open the device up to RW permissions for everyone.

• nieomylnieja: It worked! Thank you so much for that insight, I wouldn't have figured it out in a reasonable time on my own for sure, I just ran the script to add both tty and usb rules, and removed the one I made previously. I haven't tested if adding just the usb rule works but afair the perms on the tty device were alright (rw for the owner group)
• S G: could u send the exact commands u used to fix the error? @nieomylnieja
• timemage: You can try sudo "${USER}/.arduino15/packages/arduino/hardware/megaavr/1.8.8/scripts/create_dfu_udev_rule" It may work. I can't practically do that for every version of every distribution of Linux in combination with every core version and executed from every command shell. In case this isn't clear, "${USER}" will evaluate to your user name. Or rather it will in bash. 1.8.8 is current as of this comment.