Make a Periodic class, use it to blink the LED less often

src/Periodic.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <Arduino.h>
+
+/**
+ * Periodically invoke a callback.
+ * 
+ * FIXME: currently just syntatic sugar for polling in loop (you must call .loop), but eventually
+ * generalize with the freertos scheduler so we can save lots of power by having everything either in
+ * something like this or triggered off of an irq.
+ */
+class Periodic
+{
+  uint32_t lastMsec = 0;
+  uint32_t period = 1; // call soon after creation
+  uint32_t (*callback)();
+
+public:
+  // callback returns the period for the next callback invocation (or 0 if we should no longer be called)
+  Periodic(uint32_t (*_callback)()) : callback(_callback) {}
+
+  // for the time being this must be called from loop
+  void loop()
+  {
+    uint32_t now = millis();
+    if (period && (now - lastMsec) >= period)
+    {
+      lastMsec = now;
+      period = (*callback)();
+    }
+  }
+};