Firmware for a Sinner Cypreus Tri-EDC with a FET+1 driver with 
triple XP-L emitters and a capacitor to enable off-time memory.

Interface:

  See the state change diagram for details, but here is a quick 
  overview:

  - A short press (0.5s or less) moves the mode forward by one.
  - A medium press (~0.5s to 1.5s) moves the mode backward by one.
  - A long press (more than 1.5s) resets to the first mode.  So, after 
    being off for a while it always starts at the first mode.
  - Going "backward" from the first mode will take you to hidden 
    modes.
  - A short press from any hidden mode has various effects.

Solid modes:

   1. Moon.
   2. Low.
   3. Medium.
   4. High.
   5. Turbo. (will step down after ~15s)
   6. Max Turbo. (will step down after ~15s)

Primary / intermediate hidden modes:

   -1. Max Turbo.
       Short press -> Moon.
   -2. Bike flasher (bright).
       Short press -> Dim bike flasher.
   -3. 24 Hz strobe.
       Short press -> 12 Hz strobe.
   -4. Battcheck mode.
       Short press -> Heartbeat beacon.

Full / secondary hidden modes:

   7. Dim bike flasher.
   8. Medium bike flasher.
   9. Bright bike flasher.
  10. Battery check mode.  Measures, blinks 0 to 5 times, waits, repeats:
      - 0 blinks: < 3.0V
      - 1 blink : 3.0-3.5V
      - 2 blinks: 3.5-3.8V
      - 3 blinks: 3.8-4.0V
      - 4 blinks: 4.0-4.2V
      - 5 blinks: > 4.2V
  11. 1Hz Heartbeat beacon.  Blinks twice, waits, repeats.
  12. 12Hz motion-freezing strobe.  (not tactical, more like a party strobe)
  13. 24Hz motion-freezing strobe.
  14. 60Hz motion-freezing strobe.
  15. Self-ramping 7Hz to 18Hz motion-freezing strobe.  Point it 
      at a ceiling fan or something, it looks neat.
  12. Self-ramping 16Hz to 100Hz motion-freezing strobe.

Mode changes:

  See the state change diagram for a visual summary.

  There are basically three mode groups: Normal, primary hidden, and 
  full hidden.  Normal modes loop both directions except that a 
  medium press from moon enters the primary hidden group.  The 
  primary hidden group is reversed and loops back to moon at the 
  end, with each forward action going to various other places.  The 
  full hidden group loops on both ends and can only be exited by 
  doing a long press.

When the battery voltage gets low, the light will step down and 
eventually turn off.  If on a blinky mode, it'll "step down" to the 
"Med" mode first, then low, then off.  If on a regular/solid mode, 
it will step down one level each time until it's at "moon", then 
turn off.