Improve app reliability

Signed-off-by: Severin Kaderli <severin@kaderli.dev>

src/MagSend-Website/scripts/Constants.js

@@ -5,7 +5,7 @@ class Constants {
    * @type {Number}
    */
   static get CLOCK_TIME() {
-    return 1000;
+    return 500;
   }
 
   /**

src/MagSend/app/src/main/java/dev/kaderli/magsend/activity/BaseSensorActivity.kt

@@ -16,7 +16,7 @@ abstract class BaseSensorActivity : BaseActivity(), SensorEventListener {
     super.onResume()
     sensorManager = getSystemService(Context.SENSOR_SERVICE) as SensorManager
     sensor = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
-    sensorManager.registerListener(this, sensor, SensorManager.SENSOR_DELAY_UI);
+    sensorManager.registerListener(this, sensor, SensorManager.SENSOR_DELAY_GAME);
   }
 
   override fun onStop() {

src/MagSend/app/src/main/java/dev/kaderli/magsend/activity/ReceiveActivity.kt

@@ -25,6 +25,9 @@ class ReceiveActivity : BaseSensorActivity() {
    */
   private var signal = ArrayList<Sample<Signal>>()
 
+  /**
+   * Flag that determines if the preamble was already received.
+   */
   private var preambleReceived = false
 
   override fun onCreate(savedInstanceState: Bundle?) {
@@ -50,19 +53,51 @@ class ReceiveActivity : BaseSensorActivity() {
       return getMidRangeOfData() + 3
     }
 
-    return getMidRangeOfData();
+    return getMidRangeOfData() + 2
+  }
+
+  private fun getThresholdForLowSignals(): Float {
+    if (getRangeOfData() < 3) {
+      return getMidRangeOfData() + 3
+    }
+
+    return getMidRangeOfData() - 2
   }
 
   private fun getMidRangeOfData(): Float {
     val maxValue = samples.maxByOrNull { it.value } ?: Sample(0f)
     val minValue = samples.minByOrNull { it.value } ?: Sample(0f)
-    return (maxValue.value + minValue.value) / 2;
+    return (maxValue.value + minValue.value) / 2
   }
 
   private fun isHigh(value: Float): Boolean {
     return value > getThresholdForHighSignals()
   }
 
+  private fun isLow(value: Float): Boolean {
+    return value < getThresholdForLowSignals()
+  }
+
+  /**
+   * Check if the given sample should count as a high or low signal. If the sample is inside
+   * the threshold area it is not counted.
+   */
+  private fun getSignalForSample(sample: Sample<Float>): Sample<Signal>? {
+    if (isHigh(sample.value)) {
+      return Sample(Signal.High)
+    }
+
+    if (isLow(sample.value)) {
+      return Sample(Signal.Low)
+    }
+
+    return null
+  }
+
+  /**
+   * Attempts to detect the preamble in the already received signal. If it can find the preamble it returns true and
+   * false otherwise.
+   */
   private fun detectPreamble(): Boolean {
     val cleanedSignal = cleanSignal(signal)
     val compressedSignal = compressSignal(cleanedSignal)
@@ -89,9 +124,11 @@ class ReceiveActivity : BaseSensorActivity() {
     return false
   }
 
+  /**
+   * This functions takes the signal and filters out samples that are only in a cluster of 3 or less of the same signal.
+   * This way we can remove single jumps that occur in the signal.
+   */
   private fun cleanSignal(signal: List<Sample<Signal>>): List<Sample<Signal>> {
-    // TODO: Improve this method
-    // Remove outliers from the signal (single signal spikes or drops)
     val cleanSignal = signal.filterIndexed { index, sample ->
       var elementCount = 1
 
@@ -127,40 +164,51 @@ class ReceiveActivity : BaseSensorActivity() {
 
   private fun analyzePacketSignal(): List<Int> {
     val cleanedSignal = cleanSignal(signal)
-    val compressedSignal = compressSignal(cleanedSignal)
 
-    if (compressedSignal.size < 2) {
-      return listOf()
-    }
-
-    val timeDifferences = ArrayList<Long>()
-    compressedSignal.forEachIndexed { index, sample ->
+    var maxSamplesInARow = 0
+    var count = 0
+    cleanedSignal.forEachIndexed { index, sample ->
       if(index == 0) {
         return@forEachIndexed
       }
 
-      timeDifferences.add(sample.timestamp - compressedSignal[index - 1].timestamp)
+      if(sample.value == cleanedSignal[index - 1].value) {
+        count ++
+        if(count > maxSamplesInARow) {
+          maxSamplesInARow = count
+        }
+      } else {
+        count = 0
+      }
     }
 
-    val clockTimeThreshold = 900//timeDifferences.max() * 0.75
 
     val packetData = ArrayList<Int>()
-    compressedSignal.forEachIndexed { index, sample ->
-      if (index == 0) {
-        return@forEachIndexed
+    var lastSignal: Sample<Signal>? = null
+    var isFirstSignal = true
+    var samplesSinceLastSignal = 0
+    cleanedSignal.forEach { sample ->
+      if (lastSignal == null) {
+        lastSignal = sample
       }
 
-      val timeDifference = sample.timestamp - compressedSignal[index - 1].timestamp
-      if (timeDifference > clockTimeThreshold && timeDifference < 2500) {
+      if (sample.value != lastSignal!!.value) {
+        if(samplesSinceLastSignal > (maxSamplesInARow * 0.75) || isFirstSignal) {
+          //Log.i(TAG, "$samplesSinceLastSignal")
           if (sample.value == Signal.High) {
             packetData.add(0)
           } else {
             packetData.add(1)
           }
+          isFirstSignal = false
+          samplesSinceLastSignal=0
         }
+        lastSignal = sample
+      }
+      samplesSinceLastSignal++
     }
 
-    Log.i(TAG, "$timeDifferences")
+
     //Log.i(TAG, "$cleanSignal")
 
     return packetData
@@ -171,15 +219,12 @@ class ReceiveActivity : BaseSensorActivity() {
     samples.add(Sample(magneticFieldStrength))
 
     // Determine whether the sample is a high or low signal
-    val currentSignal: Sample<Signal> = if (isHigh(magneticFieldStrength)) {
-      Sample(Signal.High)
-    } else {
-      Sample(Signal.Low)
-    }
+    val currentSignal = getSignalForSample(samples.last()) ?: return
     signal.add(currentSignal)
 
     // Try to detect the preamble in the signal
     if (!preambleReceived) {
+      // If we detect the preamble we change the status on the screen and clear the existing signal data.
       if (detectPreamble()) {
         preambleReceived = true
         preambleStatus.setText(R.string.preamble_status_detected)
@@ -189,9 +234,12 @@ class ReceiveActivity : BaseSensorActivity() {
       }
     }
 
+    // After the preamble is detected we attempt to decode the packet.
     if (preambleReceived) {
-      val packet = analyzePacketSignal();
+      // Get the decoded packet data
+      val packet = analyzePacketSignal()
 
+      // Get the payload length of in the data
       var payloadLength = 0
       if (packet.size >= 4) {
         payloadLength = listToInteger(packet.take(4))
@@ -207,6 +255,7 @@ class ReceiveActivity : BaseSensorActivity() {
 
         receiveValue.text = payload
 
+        // TODO: CRC show and calculate if it's correct
         if (packet.size >= 4 + (8 * payloadLength) + 8) {
           // CRC Check
           val crc = listToInteger(packet.take(4 + (8 * payloadLength) + 8).takeLast(8))
@@ -217,7 +266,7 @@ class ReceiveActivity : BaseSensorActivity() {
   }
 
   private fun listToInteger(values: List<Int>): Int {
-    var value: Int = 0
+    var value = 0
 
     for (bit in values) {
       value = (value shl 1) + bit