Level Change Events (2)

Attach handlers on a GpioPin after configuring pull / direction / debounce, before or as you enable.

This is an example of setting a handler to trigger when a pin goes low. The method on the object is called handleGpioLow – the method name is arbitrary, but event handlers customarily start with handle then the name of the event being handled.

  // ( mr:MethodRef index:i -- )
  o:.handleGpioLow~ 0 t:.setOnLow^

Stack for both setters: ( handler:MethodRef index:i -- ) on the pin. Use index when several pins share one handler (ev.index).

This handler is used for both a “disable” and “enable” blink button; index distinguishes them. The code does a compare to the index of the enable button, then uses that bool results to set the blink field. Note that accessing the .index field still leaves the event on DS; the nip removes it.

// ( ev:Event -- ) o( inst:LedBtnCtrl )
: LedBtnCtrl#handleGpioLow
  .index@ nip
  LedBtnCtrl.idxEnable ==
  o:.blink!
;

Be careful to never leave an event on DS, because they will accumulate, possibly leading to stack overflow, but certainly polluting your stack!

Debouncing is covered in Debouncing. Event basics: Events.