feat: read demo characteristic

app/src/main/java/com/example/sensortestingapp/ConnectionManager.kt

@@ -20,9 +20,11 @@ import android.annotation.SuppressLint
 import android.bluetooth.BluetoothDevice
 import android.bluetooth.BluetoothGatt
 import android.bluetooth.BluetoothGattCallback
+import android.bluetooth.BluetoothGattCharacteristic
 import android.bluetooth.BluetoothProfile
 import android.content.Context
 import android.util.Log
+import java.util.UUID
 import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.ConcurrentLinkedQueue
 
@@ -51,6 +53,12 @@ data class MtuRequest(
 ) : BleOperationType()
 
 
+data class ReadChar(
+    override val device: BluetoothDevice,
+    val serviceId: UUID,
+    val charId: UUID
+) : BleOperationType()
+
 data class DiscoverServicesRequest(
     override val device: BluetoothDevice,
 ) : BleOperationType()
@@ -76,6 +84,22 @@ private fun BluetoothGatt.printGattTable() {
 }
 
 
+fun BluetoothGattCharacteristic.isReadable(): Boolean =
+    containsProperty(BluetoothGattCharacteristic.PROPERTY_READ)
+
+fun BluetoothGattCharacteristic.isWritable(): Boolean =
+    containsProperty(BluetoothGattCharacteristic.PROPERTY_WRITE)
+
+fun BluetoothGattCharacteristic.isWritableWithoutResponse(): Boolean =
+    containsProperty(BluetoothGattCharacteristic.PROPERTY_WRITE_NO_RESPONSE)
+
+fun BluetoothGattCharacteristic.containsProperty(property: Int): Boolean {
+    return properties and property != 0
+}
+
+fun ByteArray.toHexString(): String =
+    joinToString(separator = "", prefix = "0x") { String.format("%02X", it) }
+
 @SuppressLint("MissingPermission")
 object ConnectionManager {
 
@@ -114,6 +138,10 @@ object ConnectionManager {
 
     }
 
+    fun readChar(device: BluetoothDevice, service: UUID, char: UUID) {
+        enqueueOperation(ReadChar(device, service, char))
+    }
+
     // - Beginning of PRIVATE functions
 
     @Synchronized
@@ -192,6 +220,16 @@ object ConnectionManager {
                 gatt.discoverServices()
             }
 
+            is ReadChar -> with(operation) {
+                val characteristic = gatt.getService(serviceId)?.getCharacteristic(charId)
+                if (characteristic?.isReadable() == true) {
+                    gatt.readCharacteristic(characteristic)
+                } else {
+                    signalEndOfOperation()
+                }
+
+            }
+
 
             is Connect -> {
                 Log.e("ConnectionManager", "Shouldn't get here")
@@ -260,6 +298,41 @@ object ConnectionManager {
             }
         }
 
+        override fun onCharacteristicRead(
+            gatt: BluetoothGatt,
+            characteristic: BluetoothGattCharacteristic,
+            status: Int
+        ) {
+            with(characteristic) {
+                when (status) {
+                    BluetoothGatt.GATT_SUCCESS -> {
+                        Log.i(
+                            "ConnectionManager",
+                            "Read characteristic $uuid (service: ${service.uuid}): ${value.toHexString()}"
+                        )
+                    }
+
+                    BluetoothGatt.GATT_READ_NOT_PERMITTED -> {
+                        Log.e(
+                            "BluetoothGattCallback",
+                            "Read not permitted for $uuid (service: ${service.uuid})!"
+                        )
+                    }
+
+                    else -> {
+                        Log.e(
+                            "BluetoothGattCallback",
+                            "Characteristic read failed for $uuid (service: ${service.uuid}), error: $status"
+                        )
+                    }
+                }
+            }
+
+            if (pendingOperation is ReadChar) {
+                signalEndOfOperation()
+            }
+        }
+
 
     }
 

app/src/main/java/com/example/sensortestingapp/MainActivity.kt

@@ -27,6 +27,9 @@ import androidx.recyclerview.widget.RecyclerView
 import androidx.recyclerview.widget.SimpleItemAnimator
 import com.example.sensortestingapp.databinding.ActivityMainBinding
 import com.punchthrough.blestarterappandroid.ble.ConnectionManager
+import java.nio.ByteBuffer
+import java.nio.ByteOrder
+import java.util.UUID
 
 
 private const val ENABLE_BLUETOOTH_REQUEST_CODE = 1
@@ -39,6 +42,11 @@ private const val GATT_MAX_MTU_SIZE = 517
 // Top level declaration
 private const val GATT_REQUESTED_MTU_SIZE = GATT_MAX_MTU_SIZE
 
+
+private val DEMO_SERVICE_UUID = UUID.fromString("00000000-0001-11E1-9AB4-0002A5D5C51B")
+private val DEMO_CHAR_UUID = UUID.fromString("00140000-0001-11E1-AC36-0002A5D5C51B")
+
+
 fun Context.hasPermission(permissionType: String): Boolean {
     return ContextCompat.checkSelfPermission(this, permissionType) ==
             PackageManager.PERMISSION_GRANTED
@@ -53,6 +61,32 @@ fun Context.hasRequiredRuntimePermissions(): Boolean {
     }
 }
 
+data class DemoPayload(val ts: Int, val pressure: Float, val temperature: Float)
+
+
+fun bytesToUInt16(arr: ByteArray, start: Int): Int {
+    return ByteBuffer.wrap(arr, start, 2)
+        .order(ByteOrder.LITTLE_ENDIAN).short.toInt() and 0xFFFF
+}
+
+fun bytesToInt16(arr: ByteArray, start: Int): Short {
+    return ByteBuffer.wrap(arr, start, 2)
+        .order(ByteOrder.LITTLE_ENDIAN).short
+}
+
+fun bytesToInt32(arr: ByteArray, start: Int): Int {
+    return ByteBuffer.wrap(arr, start, 4)
+        .order(ByteOrder.LITTLE_ENDIAN).int
+}
+
+
+fun decodeDemoPayload(bytes: ByteArray): DemoPayload {
+    val ts = bytesToUInt16(bytes, 0)
+    val pressure = bytesToInt32(bytes, 2) / 100.0f
+    val temp = bytesToInt16(bytes, 6) / 10.0f;
+    return DemoPayload(ts, pressure, temp)
+}
+
 
 @SuppressLint("MissingPermission")
 class MainActivity : AppCompatActivity() {
@@ -101,9 +135,11 @@ class MainActivity : AppCompatActivity() {
             ConnectionManager.connect(scanResult.device, applicationContext)
             ConnectionManager.requestMtu(scanResult.device, Int.MAX_VALUE)
             ConnectionManager.discoverServices(scanResult.device)
+            ConnectionManager.readChar(scanResult.device, DEMO_SERVICE_UUID, DEMO_CHAR_UUID)
         }
     }
 
+
     override fun onCreate(savedInstanceState: Bundle?) {
         WindowCompat.setDecorFitsSystemWindows(window, false)
         super.onCreate(savedInstanceState)