Not sure if anyone else will run into issues like I did – I’m a QMK veteran and I’ve been using QMK toolbox to flash boards for years.

The first issue was the microcontroller type – while most boards use atmega32u4, xwhatsit uses atmega32u2.

Second issue was using the custom site at http://35.164.28.200:5000/#/xwhatsit/brand_new_model_f/f62/wcass/LAYOUT_all gave me issues because of the filename of the download.

Renaming the .hex file will do the trick.
First time will work, subsequent tries will fail because of the extra “%20(##)” string in the filename.

Sample error:

>>> dfu-programmer atmega32u2 erase –force

Erasing flash…Success

Checking memory from 0x0 to 0x6FFF…Empty.

>>> dfu-programmer atmega32u2 flash /Users/<user>/Downloads/xwhatsit_brand_new_model_f_f62_wcass_default_6523a7c%20(3).hex

Error opening /Users/<user>/Downloads/xwhatsit_brand_new_model_f_f62_wcass_default_6523a7c%20(3).hex

See –debug=51 or greater for more information.

>> dfu-programmer atmega32u2 reset

Renamed:

*** DFU device connected

*** Attempting to flash, please don’t remove device

>>> dfu-programmer atmega32u2 erase –force

Erasing flash…Success

Checking memory from 0x0 to 0x6FFF…Empty.

>>> dfu-programmer atmega32u2 flash /Users/<user>/Downloads/f62-firmware.hex

Checking memory from 0x0 to 0x55FF…Empty.

0%100%Programming 0x5600 bytes…

[>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>]Success

0%100%Reading 0x7000 bytes…

[>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>]Success

Validating…Success

0x5600 bytes written into 0x7000 bytes memory (76.79%).

>>> dfu-programmer atmega32u2 reset

*** DFU device disconnected

Hope this helps someone.