Add initial (untested) version of Arduino sketch

source/arduino/config.h

@@ -0,0 +1,11 @@
+// SSID and password of the WiFi network to which we broadcast the door lock's
+// status.
+char SSID[] = "";
+char PASSWORD[] = "";
+
+
+// Port on which to listen for status requests
+unsigned int PORT = 12345;
+
+// Pin to which the reed switch is connected
+uint8_t REED_PIN = 0;

source/arduino/door_status.ino

@@ -0,0 +1,87 @@
+#include <SPI.h>
+#include <WiFi101.h>
+#include <WiFiUdp.h>
+
+#include "config.h"
+
+uint8_t OPEN = 1;
+uint8_t CLOSED = 0;
+
+int wifi_status = WL_IDLE_STATUS;
+
+WiFiUDP Udp;
+
+void setup() {
+  pinMode(REED_PIN, INPUT_PULLUP);
+
+  Serial.begin(9600);
+  while (!Serial);
+
+  if (WiFi.status() == WL_NO_SHIELD) {
+    Serial.println("No WiFI shield present");
+    // TODO: Create noShieldLoop with visual indication.
+    while (true);
+  }
+
+  while (true) {
+    // TODO: Visually indicate that we are trying to connect
+    Serial.print("Connecting to SSID: ");
+    Serial.println(SSID);
+    status = WiFi.begin(SSID, PASSWORD);
+
+    if (status == WL_CONNECTED) {
+      break;
+    }
+
+    // TODO: Visually indicate that we waiting for trying to connect again
+    delay(10000);
+  }
+
+  printNetworkInfo();
+
+}
+
+void loop() {
+  int reed_state = digitalRead(REED_PIN);
+
+  int packetSize = Udp.readPacket();
+  if (packetSize) {
+    Udp.beginPacket(udp.remoteIP(), Udp.remotePort());
+
+    if (reed_state == HIGH) {
+      Udp.write(CLOSED);
+    } else {
+      Udp.write(OPEN);
+    }
+
+    Udp.endPacket();
+  }
+  // TODO: Visually indicate open/closed state.
+}
+
+
+void printNetworkInfo() {
+
+  Serial.print("Connect to WiFi");
+
+  IPAddress ip = WiFi.localIP();
+  Serial.print("IP Address: ");
+  Serial.println(ip);
+
+  byte mac[6];
+  WiFi.macAddress(mac);
+  Serial.print("MAC address: ");
+  for (int i = 5; i >= 0; --i) {
+    if (mac[i] < 16) {
+      Serial.print("0");
+    }
+
+    Serial.print(mac[i], HEX);
+
+    if (i > 0) {
+      Serial.print(":");
+    }
+  }
+  Serial.println();
+
+}