Thank you for the instruction.
Instead of using cmd commands in the first post, I successfully updated my D4v2 and KR4 using GUI version of AVRDUDE. I thought it was much more convenient, so I would like to share it.
Here is what I did.
1. Install Zadig (USB driver) as described in the first post.
2. Download portable AVRDUDESS 2.14 ( AVRDUDESS – A GUI for AVRDUDE | Zak’s Electronics Blog ~* ). Run avrdudess.exe and set the following options.
2-a. In “programmer” select USBasp.
2-b. In “Port” select usb
2-c. In “MCU” select ATtiny 1634
2-d. in “Flash” select your .hex file ( I downloaded my hex file from here: Index of /torches/fsm/anduril2 )
3. Place the pogo pins on the pads then hit “Detect” in MCU Panel. If the pins are properly placed, it will say it detected ATtiny1634.
4. Hit “Program!” if you get ATtiny1634 Detected message.
The whole process took about 13 seconds in my case. For me, the only hard part was to properly align 6 pogo pins, especially for KR4 because the pads were placed deeper into the tube. The less exposed pads made it hard for me to use high power magnification.
Also, I tried to read the original hex file and save it. However, it resulted in an error. After the error the programmer did not work properly for a while. I was able to use the programmer again after I reinstalled the driver and restarted the computer. I do not recommend you try to read the hex file unless you know what you are doing. I saw several instances where people had problems when they tried to read the hex file off their flashlight. When I tried reading hex file off of my flashlight, it was successful in reading the hex file, but it failed saving and displayed errors.
The above instruction on AVRDUDESS is modified version of the instruction by thefreeman ( WTS : Flashing adapters for Attiny1616 (Sofirn/Wurkkos) - #2 by thefreeman ). His instruction was for his flashing kit and I revised it a little for it to work with the flash kit from Hank. Thank you thefreeman!
Finally, I would also like to thank the OP for maintaining this thread.