Add Raspberry Pi sensor observables

src/main/java/com/easternedgerobotics/rov/io/CpuInformation.java

@@ -0,0 +1,45 @@
+package com.easternedgerobotics.rov.io;
+
+import com.easternedgerobotics.rov.value.CpuValue;
+
+import com.pi4j.system.SystemInfo;
+import rx.Observable;
+import rx.exceptions.Exceptions;
+import rx.schedulers.Schedulers;
+
+import java.io.IOException;
+import java.util.concurrent.TimeUnit;
+
+public final class CpuInformation {
+    private final Observable<Long> interval;
+
+    /**
+     * Constructs a CpuInformation instance that polls CPU properties at the specified interval.
+     *
+     * @param interval the interval at which to poll the CPU properties.
+     * @param timeUnit the {@code TimeUnit} the interval is specified in.
+     */
+    public CpuInformation(final int interval, final TimeUnit timeUnit) {
+        this.interval = Observable.interval(interval, timeUnit);
+    }
+
+    /**
+     * Returns an observable stream of CPU values.
+     *
+     * @return a stream of CPU values.
+     */
+    public final Observable<CpuValue> observe() {
+        return interval.observeOn(Schedulers.io())
+            .map(this::pollCpu)
+            .observeOn(Schedulers.immediate());
+    }
+
+    private CpuValue pollCpu(final long tick) {
+        try {
+            return CpuValue.create(
+                SystemInfo.getClockFrequencyArm(), SystemInfo.getCpuTemperature(), SystemInfo.getCpuVoltage());
+        } catch (final InterruptedException | IOException e) {
+            throw Exceptions.propagate(e);
+        }
+    }
+}

src/main/java/com/easternedgerobotics/rov/value/Cpu.java

@@ -0,0 +1,23 @@
+package com.easternedgerobotics.rov.value;
+
+class Cpu implements ImmutableValueCompanion<CpuValue> {
+    /**
+     * The ARM clock frequency.
+     */
+    public long frequency;
+
+    /**
+     * The core temperature of the main SoC in celsius.
+     */
+    public float temperature;
+
+    /**
+     * The core voltage.
+     */
+    public float voltage;
+
+    @Override
+    public CpuValue asImmutable() {
+        return new CpuValue(this);
+    }
+}

src/main/java/com/easternedgerobotics/rov/value/CpuValue.java

@@ -0,0 +1,59 @@
+package com.easternedgerobotics.rov.value;
+
+import java.util.Objects;
+
+public class CpuValue implements MutableValueCompanion<Cpu> {
+    /**
+     * Constructs a CPU value with the given frequency, temperature, and voltage.
+     *
+     * @param frequency the ARM clock frequency.
+     * @param temperature The core temperature of the main SoC in celsius.
+     * @param voltage the core voltage.
+     * @return a CPU value with the given frequency, temperature, and voltage.
+     */
+    public static CpuValue create(final long frequency, final float temperature, final float voltage) {
+        final Cpu cpu = new Cpu();
+        cpu.frequency = frequency;
+        cpu.temperature = temperature;
+        cpu.voltage = voltage;
+        return new CpuValue(cpu);
+    }
+
+    private final Cpu cpu;
+
+    CpuValue(final Cpu cpu) {
+        this.cpu = cpu;
+    }
+
+    @Override
+    public final Cpu asMutable() {
+        return cpu;
+    }
+
+    @Override
+    public final boolean equals(final Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        final CpuValue cpuValue = (CpuValue) o;
+        return Objects.equals(cpu, cpuValue.cpu);
+    }
+
+    @Override
+    public final int hashCode() {
+        return Objects.hash(cpu);
+    }
+
+    @Override
+    public final String toString() {
+        return String.format(
+            "CpuValue{frequency=%d, temperature=%f, voltage=%f}",
+            cpu.frequency,
+            cpu.temperature,
+            cpu.voltage
+        );
+    }
+}