I have an older WordClock using a Pro Trinket 3V. I was trying to reset the clock by reloading the sketch. I opened Arduino IDE and it wanted to upgrade to 2.3.8. I let it upgrade and it also wanted to upgrade some libraries. Now when I try to upload the sketch I get the following error: Using port : usb Using programmer : usbtiny Warning: cannot open USB device: Permission denied Error: cannot find USBtiny device (0x1781/0xc9f) Error: unable to open port usb for programmer usbtiny I then tried to upload using another computer without updating and it loaded correctly. I then updated the software and it generates the same error. I have tried reloading older versions of the arduino IDE software and the libraries. I'm wondering if it is a configuration problem or some error in the updated software.

There is an issue with the driver for usbtiny following a windows or ide update ( dont know which ) - there is a fix using the zadig utility to load a generic usb driver - this worked for me . If following the install keep usb tiny plugged in throughout and in device manger uninstall it and tick the remove driver (?) box first . (Meanwhile you’ll find arduinoISP still works) See here Use Zadig to install the libusb-win32 driver: Plug in USBTinyISP. Open Zadig. Select “USBTiny” from the dropdown. Choose libusb-win32 and click “Install Driver”. What a pain !( the usbtiny option didn’t appear for me (3), but carry on with 4) Mr google will find you more mentions on this .

Thanks. That worked, but I had to install WinUSB to get it to work. Not sure what caused the problem.

Cannot open USBtiny after upgrade

Development Tools Uploading

xfpd March 14, 2026, 12:13am 2

A discussion and temporary patch here... Attiny by SpenceKonde

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Cannot open USBtiny after upgrade

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