Calibrate distance calculation with temperature

lib/HomieNodes/PingNode.cpp

@@ -61,6 +61,7 @@ void PingNode::send()
     setProperty(cStatusTopic).send(valid ? "ok" : "error");
     if (valid) {
       setProperty(cDistanceTopic).send(String(_distance));
+      setProperty(cPingTopic).send(String(_ping_us));
       setProperty(cChangedTopic).send(changed ? "true": "false");
     }
   }
@@ -82,7 +83,7 @@ void PingNode::loop()
     {
       float ping_us = sonar->ping_median();
       // Calculating the distance @ 10 °C from d = t_ping /2 * c => t_ping /2 * 337 [m/s] => t_ping_us / 1e-6 * 1/2 * 337 
-      float newDistance = ping_us*0.0001685;
+      float newDistance = ping_us*_microseconds2meter;
       fixRange(&newDistance, cMinDistance, cMaxDistance);
       if (newDistance > 0) {
         _ping_us = ping_us;
@@ -118,7 +119,11 @@ void PingNode::setup()
 void PingNode::setMicrosecondsToMetersFactor(float temperatureCelcius)
 {
   //float soundSpeed = 337.0; // @ 10°C
-  float soundSpeed = 331.4 * 0.6*temperatureCelcius;
+  float soundSpeed = 331.4 + 0.6*temperatureCelcius;
+  printCaption();
+  Homie.getLogger() << cIndent 
+    << "SpeedOfSound: " << soundSpeed << " " << cUnitMetersPerSecond 
+    << " at " << temperatureCelcius << " " << cUnitDegrees << endl;
   // Calculating the distance from d = t_ping /2 * c => t_ping /2 * 337 [m/s] => t_ping_us / 1e-6 * 1/2 * 337
   _microseconds2meter = 0.5e-6 * soundSpeed;  
 }

lib/HomieNodes/PingNode.hpp

@@ -40,7 +40,7 @@ private:
 
   NewPing* sonar;
   float _distance = NAN;
-  int _ping_us = NAN;
+  int _ping_us = 0;
   float _lastDistance = 0;
   ChangeHandler _changeHandler = [](){};
   

lib/HomieNodes/RelayNode.cpp

@@ -36,9 +36,15 @@ HomieInternals::Uptime relayUptime;
 
 bool RelayNode::handleOnOff(const String &value)
 {
-  if (value == "true" || value == "false")
+  if (value == "true" || value == "false" || value == "toggle")
   {
-    setRelay(value == "true");
+    if (value == "toggle")
+    {
+      bool current = getRelayState();
+      setRelay(!current);
+    }
+    else
+      setRelay(value == "true");
     return true;
   }
   else

lib/HomieNodes/constants.hpp

@@ -5,6 +5,7 @@
 #define cUnitPercent "%"
 #define cUnitVolt "V"
 #define cUnitMeter "m"
+#define cUnitMetersPerSecond "m/s"
 #define cUnitMicrosecond "μs"
 
 // Topics