Turn dmx_into into class with state.

This is much nicer to read and in the future more state will be added to support all the rdm stuff.

wled00/dmx_input.h

@@ -0,0 +1,23 @@
+#pragma once
+#include <cstdint>
+
+/*
+ * Support for DMX/RDM input via serial (e.g. max485) on ESP32
+ * ESP32 Library from:
+ * https://github.com/sparkfun/SparkFunDMX
+ */
+class DMXInput
+{
+public:
+  void init(uint8_t rxPin, uint8_t txPin, uint8_t enPin, uint8_t inputPortNum);
+  void update(); 
+
+private:
+  uint8_t inputPortNum = 255; // TODO make this configurable
+  /// True once the dmx input has been initialized successfully
+  bool initialized = false; // true once init finished successfully
+  /// True if dmx is currently connected
+  bool connected = false;
+  /// Timestamp of the last time a dmx frame was received
+  unsigned long lastUpdate = 0;
+};