Crescendo: A ramping UI for reverse-clicky switch lights
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Instead of having specific modes and mode groups, this UI works based on 
a smooth ramp of all possible brightnesses.  It gives direct access to 
moon and maximum, plus optional memory.  The idea is that you turn it 
on, it ramps up, and you stop it when it reaches the desired level.

The ramp follows a zigzag pattern with brief pauses at both ends.  When 
it reaches the highest level, it also blinks very briefly since it can 
otherwise be hard to tell when it hit maximum.

No eeprom is modified while ramping, so it's safe to leave the light in 
ramp mode indefinitely.


UI terms:

  - Click: Fully press and release the button.  ("long press")
    Assumes that the light was off for at least a second before 
    clicking.  Is the same as half-pressing for a second or more.

  - Tap: QUICKLY half-press and release the button.  ("short press")
    Assumes the light was on before the tap.  Is best if you tap as 
    quickly as possible.


How to use
----------

From off:

  - Click:
    - Without memory: Ramp up, starting at moon.
    - With memory: 0.5s of moon, then the memorized mode and level.
      (memory is short-cycle, so a short-press will then go back to the 
      ramp at the beginning of the mode sequence)
  - Click, tap: Go directly to moon mode.
  - Click, tap, tap: Go directly to maximum output.
  - Click, tap, tap, tap: Battery check mode.
  - Click, tap 15+ times until light stops lighting up: Config mode.

In ramp mode:

  - Tap: Stop ramping and stay steady at the current level.

  - These work too, but likely won't be used much:
    - Tap, tap: Go to maximum output.
    - Tap, tap, tap: Go to battery check mode.

From the normal "steady" mode:

  - Tap: Ramp up.
  - Tap, tap: Ramp down.
  - Tap, tap, tap: Go to maximum output.
  - Tap, tap, tap, tap: Go to battery check mode.

From the "turbo" mode:

  - Tap (immediately): Advance to the next mode.
  - Tap (after 0.5s or longer): Go back to "steady" mode at the 
    previously-used level.

From any other mode (all blinkies and specials):

  - Tap: Advance to next mode.

In any mode except "off":

  - Click: Turn off.  Will reset to mem or ramp next time it's used.


Config mode
-----------

To enter config mode, quickly tap a bunch of times until the light stops 
lighting up.  It should be 16+ times.  Then it'll scroll through the 
options:

  1. Memory toggle.  Tap during the "buzz" to turn memory on or off.
  2. Thermal calibration.  Tap during the "buzz" to enter thermal 
     calibration mode.
     - Light turns on at a low level: Tap now to set default temperature 
       limit.  Otherwise, wait.
     - Light goes to full brightness: Tap at any time to set temperature 
       limit to the current temperature.  Basically, wait until it feels 
       hot, then tap.

So, to set a temperature limit:
  - Tap 16+ times.
  - Wait for the light to blink twice.
  - Tap during the "buzz".
  - Wait until the light feels hot, then click to turn it off.


Mode list
---------

  - Memory (if enabled)
  - Smooth auto-ramp
  - Steady output at last-used ramp level
  - Max/Turbo
  - Battcheck: 4 bars, 8 bars, or volts+tenths (depends how it was compiled)
  - Other special modes / blinkies; whatever was compiled in


Special modes available
-----------------------

  - Goodnight:  Slowly ramps from low to moon for an hour, then shuts 
    off.  Useful on a night stand.

  - Biking:  Pulses bright once per second but otherwise stays steady.  
    Good when you need to both see and be seen.  Comes in both medium 
    and bright flavors.  Can be compiled for a single pulse or a 
    stutter.

  - Tactical strobes:  For stunning or disorienting people.
    - Random: Pseudo-random strobe, variable speed.
    - Police: Two-speed alternating strobe.
    - Strobe: One-speed basic strobe.

  - Heart beacon:  Pulses once per second in a 2-flash heartbeat 
    pattern.  Can run for a long time.  Useful as a long-running beacon.

  - Party strobes:  Designed to freeze motion for fun visual effects.  
    Point it at moving water or spinning fans or dancing people, or walk 
    around while using it to make life feel like a bad horror movie.
    - 12 Hz
    - 24 Hz
    - 60 Hz
    - Variable (slow)
    - Variable (fast)

  - SOS:  Distress signal.

  - Memtoggle:  Turn memory on or off.  Buzzes quickly as a warning to 
    the user (and to help identify the mode visually), waits a second to 
    give people some time to skip to the next mode, then buzzes again 
    for a longer time.  To change the memory setting, turn the light off 
    during the longer buzz.


Compile-time options
--------------------

There are many options which can be enabled or disabled.  It should be 
able to run on virtually any driver, including nanjg drivers, FET+1, and 
FET+N+1.  It does not need an offtime capacitor.  Can also be compiled 
for attiny13, attiny25, attiny45, and attiny85 MCUs.  On attiny13 
though, space is limited and you may not be able to enable many special 
modes at the same time as memory.

One of the most important parts to configure is the ramp table.  This is 
very hardware-specific, especially on multi-channel drivers, so you 
should probably generate your own ramp with bin/level_calc.py .