Clean up some strings and show checksum check

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

src/MagSend/app/src/main/java/dev/kaderli/magsend/Utility.kt

@@ -0,0 +1,51 @@
+package dev.kaderli.magsend
+
+class Utility {
+  companion object {
+    /**
+     * Calculates the CRC-8-AUTOSAR checksum of the given array of bytes.
+     *
+     * This code is based on the code examples from the following page:
+     * http://www.sunshine2k.de/articles/coding/crc/understanding_crc.html
+     *
+     * The specifics of the algorithm is coming from the AUTOSAR CRC specification:
+     * https://www.autosar.org/fileadmin/user_upload/standards/classic/21-11/AUTOSAR_SWS_CRCLibrary.pdf
+     *
+     * > Utility.crc8Autosar(arrayListOf(0x0, 0x0, 0x0, 0x0)).toString(16)
+     * "12"
+     * > Utility.crc8Autosar(arrayListOf(0xF2, 0x01, 0x83)).toString(16)
+     * "c2"
+     * > Utility.crc8Autosar(arrayListOf(0x0F, 0xAA, 0x00, 0x55)).toString(16)
+     * "c6"
+     * > Utility.crc8Autosar(arrayListOf(0x00, 0xff, 0x55, 0x11)).toString(16)
+     * "77"
+     * > Utility.crc8Autosar(arrayListOf(0x33, 0x22, 0x55, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff)).toString(16)
+     * "11"
+     * > Utility.crc8Autosar(arrayListOf(0x92, 0x6b, 0x55)).toString(16)
+     * "33"
+     * > Utility.crc8Autosar(arrayListOf(0xff, 0xff, 0xff, 0xff)).toString(16)
+     * "6c"
+     */
+    fun crc8Autosar(bytes: List<Int>): Int {
+      val polynomial = 0x2f;
+      val xorOut = 0xff;
+      var crc = 0xff;
+
+      for (byte in bytes) {
+        crc = crc xor byte;
+
+        for(i in 1..8) {
+          crc = if ((crc and 0x80) != 0) {
+            ((crc shl 1) xor polynomial) and 0xff;
+          } else {
+            crc shl 1
+          }
+        }
+      }
+
+      return crc xor xorOut;
+    }
+  }
+
+
+}

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

@@ -27,6 +27,7 @@ abstract class BaseSensorActivity : BaseActivity(), SensorEventListener {
   override fun onAccuracyChanged(sensor: Sensor?, accuracy: Int) {}
 
   override fun onSensorChanged(event: SensorEvent) {
+    // Calculate the absolute magnetic field strength
     val magneticFieldStrength = sqrt(event.values[0].pow(2) + event.values[1].pow(2) + event.values[2].pow(2))
     sensorValueReceived(magneticFieldStrength)
   }

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

@@ -1,17 +1,20 @@
 package dev.kaderli.magsend.activity
 
 import android.os.Bundle
-import android.util.Log
 import android.view.View
 import android.widget.TextView
 import androidx.core.content.ContextCompat
 import dev.kaderli.magsend.R
+import dev.kaderli.magsend.Utility
 import dev.kaderli.magsend.model.Sample
 import dev.kaderli.magsend.model.Signal
 import java.lang.Integer.min
+import java.util.stream.Collectors
 
 class ReceiveActivity : BaseSensorActivity() {
+  private lateinit var receiveDescription: TextView
   private lateinit var preambleStatus: TextView
+  private lateinit var crcStatus: TextView
   private lateinit var headerStatus: TextView
   private lateinit var receiveValue: TextView
 
@@ -30,9 +33,13 @@ class ReceiveActivity : BaseSensorActivity() {
    */
   private var preambleReceived = false
 
+  private var receivingComplete = false
+
   override fun onCreate(savedInstanceState: Bundle?) {
     super.onCreate(savedInstanceState)
+    receiveDescription = findViewById(R.id.receiveDescription)
     preambleStatus = findViewById(R.id.preambleStatus)
+    crcStatus = findViewById(R.id.crcStatus)
     headerStatus = findViewById(R.id.headerStatus)
     receiveValue = findViewById(R.id.receiveValue)
   }
@@ -168,13 +175,13 @@ class ReceiveActivity : BaseSensorActivity() {
     var maxSamplesInARow = 0
     var count = 0
     cleanedSignal.forEachIndexed { index, sample ->
-      if(index == 0) {
+      if (index == 0) {
         return@forEachIndexed
       }
 
-      if(sample.value == cleanedSignal[index - 1].value) {
+      if (sample.value == cleanedSignal[index - 1].value) {
-        count ++
+        count++
-        if(count > maxSamplesInARow) {
+        if (count > maxSamplesInARow) {
           maxSamplesInARow = count
         }
       } else {
@@ -182,7 +189,6 @@ class ReceiveActivity : BaseSensorActivity() {
       }
     }
 
-
     val packetData = ArrayList<Int>()
     var lastSignal: Sample<Signal>? = null
     var isFirstSignal = true
@@ -193,28 +199,28 @@ class ReceiveActivity : BaseSensorActivity() {
       }
 
       if (sample.value != lastSignal!!.value) {
-        if(samplesSinceLastSignal > (maxSamplesInARow * 0.75) || isFirstSignal) {
+        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
+          samplesSinceLastSignal = 0
         }
         lastSignal = sample
       }
       samplesSinceLastSignal++
     }
 
-
-    //Log.i(TAG, "$cleanSignal")
-
     return packetData
   }
 
   override fun sensorValueReceived(magneticFieldStrength: Float) {
+    if (receivingComplete) {
+      return;
+    }
+
     // Add the current received sensor value to the samples
     samples.add(Sample(magneticFieldStrength))
 
@@ -252,14 +258,26 @@ class ReceiveActivity : BaseSensorActivity() {
         for (i in 1..numberOfAvailablePayloadBytes) {
           payload += listToInteger(packet.take(4 + (8 * i)).takeLast(8)).toChar().toString()
         }
-
         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))
+          val receivedCrc = listToInteger(packet.take(4 + (8 * payloadLength) + 8).takeLast(8))
-          Log.i(TAG, "CRC: $crc")
+          val calculatedCrc =
+            Utility.crc8Autosar(receiveValue.text.codePoints().boxed().collect(Collectors.toList()))
+
+          if (receivedCrc == calculatedCrc) {
+            crcStatus.setText(R.string.crc_status_valid)
+            crcStatus.setTextColor(ContextCompat.getColor(this, R.color.success))
+          } else {
+            crcStatus.setText(R.string.crc_status_invalid)
+            crcStatus.setTextColor(ContextCompat.getColor(this, R.color.error))
+          }
+
+          // Mark receiving as complete
+          receiveDescription.setText(R.string.receive_description_complete)
+          receivingComplete = true
         }
       }
     }
@@ -278,8 +296,15 @@ class ReceiveActivity : BaseSensorActivity() {
 
   fun restartReceiveProcess(view: View) {
     preambleReceived = false
+    receivingComplete = false
+
+    receiveDescription.setText(R.string.receive_description)
     preambleStatus.setText(R.string.preamble_status_not_detected)
     preambleStatus.setTextColor(ContextCompat.getColor(this, R.color.error))
+    headerStatus.text = ""
+    crcStatus.text = ""
+    receiveValue.text = ""
+
     samples.clear()
     signal.clear()
   }

src/MagSend/app/src/main/res/layout/activity_receive.xml

@@ -8,7 +8,7 @@
 
   <TextView
     android:id="@+id/receiveDescription"
-    android:layout_width="wrap_content"
+    android:layout_width="0dp"
     android:layout_height="wrap_content"
     android:layout_marginTop="@dimen/layout_margins"
     android:paddingHorizontal="@dimen/layout_margins"
@@ -21,10 +21,10 @@
     android:id="@+id/preambleStatus"
     android:layout_width="0dp"
     android:layout_height="wrap_content"
-    android:layout_marginTop="@dimen/component_spacing_small"
+    android:layout_marginTop="@dimen/component_spacing"
     android:paddingHorizontal="@dimen/layout_margins"
     android:text="@string/preamble_status_not_detected"
-    android:textColor="#FF0000"
+    android:textColor="@color/error"
     app:layout_constraintEnd_toEndOf="parent"
     app:layout_constraintStart_toStartOf="parent"
     app:layout_constraintTop_toBottomOf="@+id/receiveDescription" />
@@ -40,21 +40,31 @@
     app:layout_constraintTop_toBottomOf="@+id/preambleStatus" />
 
   <TextView
-    android:id="@+id/receiveValue"
+    android:id="@+id/crcStatus"
-    android:layout_width="wrap_content"
+    android:layout_width="0dp"
     android:layout_height="wrap_content"
-    android:layout_marginTop="@dimen/component_spacing"
+    android:layout_marginTop="@dimen/component_spacing_small"
-    android:text="___"
+    android:paddingHorizontal="@dimen/layout_margins"
-    android:textSize="48sp"
+    android:textColor="@color/success"
     app:layout_constraintEnd_toEndOf="parent"
     app:layout_constraintStart_toStartOf="parent"
     app:layout_constraintTop_toBottomOf="@+id/headerStatus" />
 
   <TextView
-    android:id="@+id/restartDescription"
+    android:id="@+id/receiveValue"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_marginTop="@dimen/component_spacing"
+    android:textSize="48sp"
+    app:layout_constraintEnd_toEndOf="parent"
+    app:layout_constraintStart_toStartOf="parent"
+    app:layout_constraintTop_toBottomOf="@+id/crcStatus" />
+
+  <TextView
+    android:id="@+id/restartDescription"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    android:layout_marginTop="@dimen/component_spacing_large"
     android:paddingHorizontal="@dimen/layout_margins"
     android:text="@string/restart_description"
     app:layout_constraintEnd_toEndOf="parent"

src/MagSend/app/src/main/res/values/colors.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-    <color name="error">#FFFF0000</color>
+    <color name="error">#FFFF5454</color>
-    <color name="success">#FF00FF00</color>
+    <color name="success">#FF4BB543</color>
 </resources>

src/MagSend/app/src/main/res/values/dimens.xml

@@ -4,4 +4,5 @@
   <dimen name="component_spacing">24dp</dimen>
   <dimen name="title_text_size">48sp</dimen>
   <dimen name="component_spacing_small">8dp</dimen>
+    <dimen name="component_spacing_large">48dp</dimen>
 </resources>

src/MagSend/app/src/main/res/values/strings.xml

@@ -5,7 +5,7 @@
   <string name="receive_button_label">Receive</string>
   <string name="calibrate_button_label">Calibrate</string>
   <string name="calibration_description">Open up the website and start the calibration mode.  Put your Smartphone on different locations on the sending device and note the value below.  The location with the highest value is the most optimal for data transmission.</string>
-  <string name="receive_description">Currently listening for transmissions.  The text that was received so far is displayed below.</string>
+  <string name="receive_description">Currently listening for transmissions.\nThe text that was received so far is displayed below.</string>
   <string name="restart_description">To start listening to a new message click the following button.</string>
   <string name="restart_button_label">Restart</string>
   <string name="calibration_activity_label">Calibration</string>
@@ -14,4 +14,7 @@
   <string name="preamble_status_not_detected">Preamble not detected X</string>
   <string name="preamble_status_detected">Preamble detected ✓</string>
   <string name="payload_length">The payload length is %1$d bytes</string>
+  <string name="receive_description_complete">The transmission is completed.\nThe received text is displayed below.</string>
+  <string name="crc_status_valid">The checksum is valid ✓.</string>
+  <string name="crc_status_invalid">The checksum is invalid X.</string>
 </resources>