Waveform Input¶

Overview¶

A Waveform Input generates a timed value — a waveform — in response to the
edges of another input. When the observed input switches on or off, it plays back a
sequence of (time, value) points you define. Typical uses are clutch-by-wire
engage on button press and release on button release, blinker / hazard
lights, and simple test signals. It watches an input you already configured and
produces a value from it.

Prerequisites & hardware¶

• A source input to observe — usually a button or switch (for example a
  Digital Input). Create it first and note its identifier.
• The observed input is treated as digital: a value < 512 is LOW, a value
  ≥ 512 is HIGH.
  • A LOW → HIGH transition fires the RISE trigger.
  • A HIGH → LOW transition fires the FALL trigger.
• At startup no transition is detected, so the first trigger can occur no earlier
  than the second cycle.

Add it in the app¶

1. Add a new input and choose Waveform Input as the type.
2. Set the Observed input to the source you want to watch.
3. Give it a clear alias (e.g. Clutch Command).
4. Define the Rise waveform and Fall waveform as lists of (time, value)
   points.
5. Set the idle values and the repeat / minimum repeats behaviour.

Settings reference¶

Schema: config/WaveformInputConfigData.proto.

How a waveform is described¶

Each waveform is a list of (time, value) points. After a trigger, a timer starts
at 0 ms and the input outputs the value scheduled for the elapsed time, linearly
interpolating between points to give a smooth ramp:

value
 1000 |          ______
      |         /
    0 |________/
      +--------+----+----> time (ms)
      0       200  300
   points: (0,0) (200,1000) (300,1000)   -> interpolated between points

When the timer passes the last point, the input either holds the idle value
(repeat off) or resets to 0 ms and plays again (repeat on).

Common settings¶

Waveform Input also uses the shared setting — alias. See
Common IO Settings.

Example — clutch engage on press, ramped release on release¶

Watch a clutch button (a Digital Input) and drive a clutch
command from 0 (open) to 1000 (closed).

1. Type Waveform Input, alias Clutch Command, Observed input = the
   clutch button.
2. Rise waveform (button pressed → engage quickly):
   (0 ms, 0) → (200 ms, 1000) — ramps up over 200 ms.
3. Fall waveform (button released → ramp out gently):
   (0 ms, 1000) → (600 ms, 0) — ramps down over 600 ms.
4. Rise repeat off, Fall repeat off — each plays once, then holds idle.
5. Idle value (LOW) 0, Idle value (HIGH) 1000 — so once engaged it
   stays closed and once released it stays open.

For a hazard light instead: put a square pulse in the Rise waveform and turn
Rise repeat on so it blinks continuously until the next trigger.

Troubleshooting¶

• Nothing happens on the first press: at startup no edge exists; the first
  trigger comes no earlier than the second cycle. Toggle the input once.
• Waveform never stops / keeps looping: repeat is on. Turn it off for a
  one-shot, or set minimum repeats so the next trigger can interrupt it.
• A new press is ignored mid-play: minimum repeats is too high — lower it
  (or use 0) so the next trigger can interrupt.
• Output sits at the wrong level between presses: check Idle value (LOW/HIGH).
• Ramp too fast or too slow: adjust the point timestamps — the output
  interpolates linearly between consecutive points.
• Triggers fire on the wrong edge: LOW/HIGH is split at 512 — make sure the
  observed input crosses that threshold.

Related¶

• Digital Input — a typical button/switch source to observe.
• Constant Value Input — a fixed value with no timing.
• Counter Input — count edges rather than play a waveform.