Modified begin function on MKRTherm.cpp

Modified Begin function, on MKRTherm.cpp, in order to return error if shield not present.

Author: Rocketct

examples/ReadSensor/ReadSensor.ino

@@ -20,7 +20,10 @@ void setup() {
 
   while (!Serial);
 
-  THERM.begin();
+  if (!THERM.begin()) {
+    Serial.println("Failed to initialize MKR Therm shield!");
+    while (1);
+  }
 }
 
 void loop() {

src/MKRTherm.cpp

@@ -28,10 +28,19 @@ THERMClass::THERMClass(int cs, SPIClass& spi) :
 
 int THERMClass::begin()
 {
+  uint32_t rawword;
+
   pinMode(_cs, OUTPUT);
   digitalWrite(_cs, HIGH);
   _spi->begin();
 
+  rawword = readSensor();
+  if (rawword == 0xFFFFFF) {
+    end();
+
+    return 0;
+  }
+
   return 1;
 }
 
@@ -64,7 +73,6 @@ uint32_t THERMClass::readSensor()
   return read;
 }
 
-
 float THERMClass::readTemperature()
 {
   uint32_t rawword;
@@ -91,8 +99,6 @@ float THERMClass::readTemperature()
   return celsius;
 }
 
-
-
 float THERMClass::readInternalTemperature()
 {
   uint32_t rawword;