TI LM74 Temperature Sensor Implementation

bulldog-devices/src/main/java/io/silverspoon/bulldog/devices/sensors/LM74TemperatureSensor.java

@@ -0,0 +1,111 @@
+package io.silverspoon.bulldog.devices.sensors;
+
+import java.io.IOException;
+
+import io.silverspoon.bulldog.core.gpio.DigitalOutput;
+import io.silverspoon.bulldog.core.io.bus.spi.SpiBus;
+import io.silverspoon.bulldog.core.io.bus.spi.SpiConnection;
+import io.silverspoon.bulldog.core.io.bus.spi.SpiDevice;
+import io.silverspoon.bulldog.core.io.bus.spi.SpiMessage;
+import io.silverspoon.bulldog.core.util.BulldogUtil;
+
+/**
+ * Texas Instruments LM74 temperature sensor implementation.
+ * 
+ * @author <a href="mailto:[email protected]">Matej Perejda</a>
+ *
+ */
+public class LM74TemperatureSensor extends SpiDevice {
+
+   private DigitalOutput digitalOutput = null;
+
+   /**
+    * This constructor is disabled. It can be used just if DigitalOutput is initialized.
+    * 
+    * @param connection
+    */
+   private LM74TemperatureSensor(SpiConnection connection) {
+      super(connection);
+   }
+
+   /**
+    * This constructor is disabled. It can be used just if DigitalOutput is initialized.
+    * 
+    * @param bus
+    * @param address
+    */
+   private LM74TemperatureSensor(SpiBus bus, int address) {
+      super(bus, address);
+   }
+
+   public LM74TemperatureSensor(SpiConnection connection, DigitalOutput digitalOutput) {
+      super(connection);
+      this.digitalOutput = digitalOutput;
+   }
+
+   /**
+    * LM74 activation signal. LM74'll be activated when signal goes from 1 to 0.
+    */
+   public void initSensor() {
+      digitalOutput.low();
+      digitalOutput.toggle();
+      BulldogUtil.sleepMs(500);
+   }
+
+   /**
+    * Reading a temperature from temp sensor. Two's complement calculation.
+    * 
+    * @see Page 11: http://www.ti.com/lit/ds/symlink/lm74.pdf
+    * @return float temperature value
+    * @throws IOException
+    **/
+   public float readTemperature() throws IOException {
+
+      float temperature = 0;
+      int bitShift;
+
+      this.initSensor();
+      this.open();
+
+      // sending bytes
+      byte[] buffer = new byte[] {(byte) 0x00, (byte) 0x00};
+
+      try {
+         SpiMessage message = this.transfer(buffer);
+
+         byte[] rec = message.getReceivedBytes();
+
+         int rec_0 = rec[0] & 0xFF;
+
+         int merged = (((BulldogUtil.getUnsignedByte(rec[0]) << 8)) | BulldogUtil.getUnsignedByte(rec[1]));
+         int first = rec_0 & Integer.parseInt("80", 16);
+
+         // negative temperature
+         // first binary digit 1 represents negative value
+         // 128 = b10000000
+         if (first == 128) {
+            int substr = merged - 1;
+            short inverted = (short) ~substr;
+            bitShift = inverted >> 3;
+            temperature = (float) (bitShift * 0.0625 * -1f);
+         }
+         // positive temperature
+         else {
+            bitShift = merged >> 3;
+            temperature = (float) (bitShift * 0.0625);
+         }
+
+         // chip shutdown
+         buffer = new byte[] {(byte) 0xFF};
+
+         this.transfer(buffer);
+
+         return temperature;
+      } catch (IOException e) {
+         throw new IOException("Something went wrong! SpiMessage was not transfered.");
+      } finally {
+         this.close();
+      }
+   }
+
+}