Modified Weatherstation Codelab Activity to handle CPU temperature

WeatherStationActivity.java

/*
 * Copyright 2017, The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.androidthings.weatherstation;

import android.app.Activity;
import android.graphics.Color;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.Handler;
import android.support.annotation.NonNull;
import android.util.Log;

import com.google.android.things.contrib.driver.apa102.Apa102;
import com.google.android.things.contrib.driver.bmx280.Bmx280SensorDriver;
import com.google.android.things.contrib.driver.ht16k33.AlphanumericDisplay;

import java.io.IOException;
import java.io.RandomAccessFile;
import java.text.DecimalFormat;
import java.util.Arrays;

import rx.Observable;
import rx.Subscriber;
import rx.android.schedulers.AndroidSchedulers;
import rx.schedulers.Schedulers;

public class WeatherStationActivity extends Activity {
    private static final String TAG = WeatherStationActivity.class.getSimpleName();

    public static final String CPU_FILE_PATH = "/sys/class/thermal/thermal_zone0/temp";
    private static final float HEATING_COEFFICIENT = 0.55f;
	private static final long UPDATE_CPU_DELAY = 50;

	private SensorManager mSensorManager;

    // Default LED brightness
    private static final int LEDSTRIP_BRIGHTNESS = 1;

    private AlphanumericDisplay mDisplay;
    private Apa102 mLedstrip;
    private Bmx280SensorDriver mEnvironmentalSensorDriver;

	private Float mCpuTemperature = 0f;
	private Observable<Float> mCpuTemperatureObservable;
	private Handler mHandler;

	@Override protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "Weather Station Started");

        // Initialize 7-segment display
        try {
            mDisplay = new AlphanumericDisplay(BoardDefaults.getI2cBus());
            mDisplay.setEnabled(true);
            mDisplay.display("0042");
            Log.d(TAG, "Initialized I2C Display");
        } catch (IOException e) {
            throw new RuntimeException("Error initializing display", e);
        }

        // Initialize LED strip
        try {
            mLedstrip = new Apa102(BoardDefaults.getSpiBus(), Apa102.Mode.BGR);
            mLedstrip.setBrightness(LEDSTRIP_BRIGHTNESS);
            int[] colors = new int[7];
            Arrays.fill(colors, Color.RED);
            mLedstrip.write(colors);
            Log.d(TAG, "Initialized SPI LED strip");
        } catch (IOException e) {
            throw new RuntimeException("Error initializing LED strip", e);
        }

        // Initialize temperature/pressure sensors
        try {
            mEnvironmentalSensorDriver = new Bmx280SensorDriver(BoardDefaults.getI2cBus());
            // Register the drivers with the framework
            mEnvironmentalSensorDriver.registerTemperatureSensor();
            mEnvironmentalSensorDriver.registerPressureSensor();

            Log.d(TAG, "Initialized I2C BMP280");
        } catch (IOException e) {
            throw new RuntimeException("Error initializing BMP280", e);
        }

        mSensorManager = getSystemService(SensorManager.class);

        // create observable for CPI temperature
		mCpuTemperatureObservable = getCpuTemperatureObservable();
		mCpuTemperatureObservable.subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread());

		mHandler = new Handler();
		mHandler.post(mTemperatureRunnable);
	}

	private Runnable mTemperatureRunnable = new Runnable() {
		@Override public void run() {
			mCpuTemperatureObservable.subscribe(new Subscriber<Float>() {
				@Override public void onCompleted() {
					Log.e(WeatherStationActivity.TAG, "Completed.");
				}

				@Override public void onError(Throwable e) {
					Log.e(WeatherStationActivity.TAG, "Error: " + e.getMessage());
				}

				@Override public void onNext(Float resultCpuTemperature) {
					// Log.i(WeatherStationActivity.TAG, "Temp: " + resultCpuTemperature); // for debugging
					mCpuTemperature = resultCpuTemperature;
				}
			});

			mHandler.postDelayed(mTemperatureRunnable, UPDATE_CPU_DELAY);
		}
	};

	@Override protected void onStart() {
        super.onStart();

        // Register for sensor events here
        // Register the BMP280 temperature sensor
        Sensor temperature = mSensorManager.getDynamicSensorList(Sensor.TYPE_AMBIENT_TEMPERATURE).get(0);
        mSensorManager.registerListener(mSensorEventListener, temperature, SensorManager.SENSOR_DELAY_NORMAL);
        // Register the BMP280 pressure sensor
        Sensor pressure = mSensorManager.getDynamicSensorList(Sensor.TYPE_PRESSURE).get(0);
        mSensorManager.registerListener(mSensorEventListener, pressure, SensorManager.SENSOR_DELAY_NORMAL);
    }

    @Override protected void onStop() {
        super.onStop();

        // Unregister for sensor events here
        mSensorManager.unregisterListener(mSensorEventListener);
    }

    @Override protected void onDestroy() {
        super.onDestroy();

        mHandler.removeCallbacks(mTemperatureRunnable);

        // Close peripheral connections here
        if (mDisplay != null) {
            try {
                mDisplay.clear();
                mDisplay.setEnabled(false);
                mDisplay.close();
            } catch (IOException e) {
                Log.e(TAG, "Error closing display", e);
            } finally {
                mDisplay = null;
            }
        }

        if (mLedstrip != null) {
            try {
                mLedstrip.write(new int[7]);
                mLedstrip.setBrightness(0);
                mLedstrip.close();
            } catch (IOException e) {
                Log.e(TAG, "Error closing LED strip", e);
            } finally {
                mLedstrip = null;
            }
        }

        if (mEnvironmentalSensorDriver != null) {
            try {
                mEnvironmentalSensorDriver.close();
            } catch (IOException e) {
                Log.e(TAG, "Error closing sensors", e);
            } finally {
                mEnvironmentalSensorDriver = null;
            }
        }
    }

    /**
     * Update the 7-segment display with the latest temperature value.
     *
     * @param temperature Latest temperature value.
     */
    private void updateTemperatureDisplay(float temperature) {
        // Add code to write a value to the segment display
        if (mDisplay != null) {
            try {
                // calculate temperature given proximity to CPU
                if(mCpuTemperature > temperature) temperature =
			                (temperature - HEATING_COEFFICIENT * mCpuTemperature) / (1 - HEATING_COEFFICIENT);
				mDisplay.display(new DecimalFormat("##").format(temperature));
			} catch (IOException e) {
                Log.e(TAG, "Error updating display", e);
            }
        }
    }

    /**
     * Update LED strip based on the latest pressure value.
     *
     * @param pressure Latest pressure value.
     */
    private void updateBarometerDisplay(float pressure) {
        // Add code to send color data to the LED strip
        if (mLedstrip != null) {
            try {
                int[] colors = RainbowUtil.getWeatherStripColors(pressure);
                mLedstrip.write(colors);
            } catch (IOException e) {
                Log.e(TAG, "Error updating ledstrip", e);
            }
        }
    }

    // Callback when SensorManager delivers new data.
    private SensorEventListener mSensorEventListener = new SensorEventListener() {
        @Override public void onSensorChanged(SensorEvent event) {
            final float value = event.values[0];

            if (event.sensor.getType() == Sensor.TYPE_AMBIENT_TEMPERATURE) {
                updateTemperatureDisplay(value);
            }
            if (event.sensor.getType() == Sensor.TYPE_PRESSURE) {
                updateBarometerDisplay(value);
            }
        }

        @Override public void onAccuracyChanged(Sensor sensor, int accuracy) {
            Log.d(TAG, "accuracy changed: " + accuracy);

        }
    };

	/**
	 * Creates an observable which reads the CPU temperature from the file system.
	 *
	 * @return the observable
	 */
	@NonNull private Observable<Float> getCpuTemperatureObservable() {
		return Observable.create(new Observable.OnSubscribe<Float>() {
			@Override public void call(Subscriber<? super Float> subscriber) {
				RandomAccessFile reader = null;
				try {
					reader = new RandomAccessFile(CPU_FILE_PATH, "r");
					String rawTemperature = reader.readLine();
					float cpuTemperature = Float.parseFloat(rawTemperature) / 1000f;
					// Log.i(WeatherStationActivity.TAG, "Parsed temp: " + cpuTemperature);  // for debugging
					subscriber.onNext(cpuTemperature);
				} catch (IOException ex) {
					ex.printStackTrace();
					subscriber.onError(ex);
				} finally {
					if(reader != null) try {
						reader.close();
					} catch (IOException e) {
						e.printStackTrace();
						subscriber.onError(e);
					}
				}
			}
		});
	}

}