split off the DHT11 conversion, corrected the algorithm for temperatures below 0 degrees celsius.

Author: sijskes

DHT.cpp

@@ -39,6 +39,15 @@ float DHT::readTemperature(bool S, bool force) {
   if (read(force)) {
     switch (_type) {
     case DHT11:
+      f = data[2];
+      if (data[3] & 0x80) {
+        f *= -1 -f ;
+      }
+      f += (data[3] & 0x0f) * 0.1;
+      if(S) {
+        f = convertCtoF(f);
+      }
+      break;
     case DHT12:
       f = data[2];
       f += (data[3] & 0x0f) * 0.1;