mhz16: Split the getData(int* gas, int *temp) function into two separate functions and updated the C++ an Java examples

Signed-off-by: Stefan Andritoiu <stefan.andritoiu@intel.com>
Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

examples/c++/mhz16.cxx

@@ -62,14 +62,15 @@ int main (int argc, char **argv)
 
   sleep(1);
 
-  int gas;
-  int temp;
-
   while (shouldRun)
     {
-      co2->getData(&gas, &temp);
+      if(!co2->getData()){
-      cout << "CO2 concentration: " << gas << " PPM, "
+        cerr << "Failed to retrieve data" << endl;
-           << "Temperature (in C): " << temp <<endl;
+        continue;
+      }
+
+      cout << "CO2 concentration: " << co2->getGas() << " PPM, "
+           << "Temperature (in C): " << co2->getTemperature() <<endl;
 
       sleep(2);
     }

examples/java/MHZ16Sample.java

@@ -36,9 +36,6 @@ public class MHZ16Sample {
 
 	public static void main(String[] args) throws InterruptedException {
 		// ! [Interesting]
-		int[] gas = new int[1];
-		int[] temp = new int[1];
-
 		// Instantiate a MHZ16 serial CO2 sensor on uart 0.
 		upm_mhz16.MHZ16 co2 = new upm_mhz16.MHZ16(0);
 
@@ -48,9 +45,12 @@ public class MHZ16Sample {
 		System.out.println("but rather the temperature of the sensor elements.");
 
 		while (true) {
-			co2.getData(gas, temp);
+			if (!co2.getData()) {
-			System.out.println("CO2 concentration: " + gas[0] + "PPM, Temperature (in C): "
+				System.out.println("Failed to retrieve data");
-					+ temp[0]);
+				continue;
+			}
+			System.out.println("CO2 concentration: " + co2.getGas() + "PPM, Temperature (in C): "
+					+ co2.getTemperature());
 
 			Thread.sleep(2000);
 		}

src/mhz16/mhz16.cxx

@@ -183,7 +183,7 @@ bool MHZ16::verifyPacket(uint8_t *pkt, int len)
   return true;
 }
 
-bool MHZ16::getData(int *gas, int *temp)
+bool MHZ16::getData()
 {
   // the query command
   const unsigned char cmd[9] = 
@@ -214,12 +214,22 @@ bool MHZ16::getData(int *gas, int *temp)
   verifyPacket(packet, sizeof(packet));
 
   // pull out the data and return it.
-  *gas = (packet[2] << 8) | packet[3];
+  gas = (packet[2] << 8) | packet[3];
-  *temp = packet[4] - 40;
+  temp = packet[4] - 40;
 
   return true;
 }
 
+int MHZ16::getGas()
+{
+  return gas;
+}
+
+int MHZ16::getTemperature()
+{
+  return temp;
+}
+
 void MHZ16::calibrateZeroPoint()
 {
   // the query command

src/mhz16/mhz16.h

@@ -135,14 +135,27 @@ namespace upm {
     bool verifyPacket(uint8_t *pkt, int len);
 
     /**
-     * Queries the sensor and returns gas (CO2) concentration and
+     * Queries the sensor and gets the gas (CO2) concentration and
      * temperature data.
+     * Should be called before other "get" functions.
      *
-     * @param gas Returned gas concentration
-     * @param temp Returned temperature in Celsius
      * @return True if successful
      */
-    bool getData(int *gas, int *temp);
+    bool getData();
+
+    /**
+     * Returns the gas (CO2) concentration data.
+     *
+     * @return Gas concentration
+     */
+    int getGas();
+
+    /**
+     * Returns the temperature data.
+     *
+     * @return Temperature in Celsius
+     */
+    int getTemperature();
 
     /**
      * Sets the zero point of the sensor
@@ -156,6 +169,8 @@ namespace upm {
   private:
     mraa_uart_context m_uart;
     int m_ttyFd;
+    int gas;
+    int temp;
   };
 }