I have an updated version.
I made this FW especially for a 3-LED SRK that I bought cheap through eBay. I got the BLF SRK FET board from RMM.
The UI is inspired by the Olight S20 Baton. Instead of blinking modes, I added the ability to cycle down the level by double clicking from ON. In the Baton, that would switch to blink modes.
The FW uses EEPROM for the mode table, so you will need to program the EEPROM using this avrdude command line.
avrdude -p t13 -c usbasp -u -D -Uflash:w:dth_Momentary.hex:a -Ueeprom:w:dth_Momentary.eep:a -Ulfuse:w:0x75:m -Uhfuse:w:0xff:m