diff --git a/android/app/src/main/java/com/eddy/atomrelay/SettingsActivity.kt b/android/app/src/main/java/com/eddy/atomrelay/SettingsActivity.kt
index 39c49d5..6a0a7bc 100644
--- a/android/app/src/main/java/com/eddy/atomrelay/SettingsActivity.kt
+++ b/android/app/src/main/java/com/eddy/atomrelay/SettingsActivity.kt
@@ -37,6 +37,10 @@ class SettingsActivity : AppCompatActivity() {
         private const val CDC_DATA_INTERFACE_CLASS = 0x0A
         private const val KEY_TIMEOUT_MS = 5000L
         private const val SET_KEY_TIMEOUT_MS = 5000L
+        private const val MAX_KEY_RETRIES = 5
+        private const val KEY_SETTLE_MS = 1000L
+        private const val RESPONSE_WAIT_MS = 500L
+        private const val USB_BULK_TIMEOUT_MS = 1000
         private const val ACTION_USB_PERMISSION = "com.eddy.atomrelay.USB_PERMISSION"
         private const val STYLE_SPINNER = 0
         private const val STYLE_HORIZONTAL = 1
@@ -347,20 +351,20 @@ class SettingsActivity : AppCompatActivity() {
         try {
             setupCdcControl(connection, device)
 
-            for (attempt in 1..5) {
-                Thread.sleep(1000L)
+            for (attempt in 1..MAX_KEY_RETRIES) {
+                Thread.sleep(KEY_SETTLE_MS)
 
                 flushReadBuffer(connection, epIn)
 
                 val cmd = "KEY?\n".toByteArray(StandardCharsets.US_ASCII)
-                val written = connection.bulkTransfer(epOut, cmd, cmd.size, 1000)
+                val written = connection.bulkTransfer(epOut, cmd, cmd.size, USB_BULK_TIMEOUT_MS)
                 Log.d(TAG, "Attempt $attempt: Sent KEY? ($written bytes)")
                 if (written < 0) {
                     Log.w(TAG, "Write failed on attempt $attempt")
                     continue
                 }
 
-                Thread.sleep(500)
+                Thread.sleep(RESPONSE_WAIT_MS)
 
                 val response = readResponse(connection, epIn, KEY_TIMEOUT_MS)
                 Log.d(TAG, "Attempt $attempt response: ${response.take(300)}")
@@ -380,13 +384,13 @@ class SettingsActivity : AppCompatActivity() {
                     val newKey = generateRandomHexKey()
 
                     val setKeyCmd = "SET_KEY:$newKey\n".toByteArray(StandardCharsets.US_ASCII)
-                    val w = connection.bulkTransfer(epOut, setKeyCmd, setKeyCmd.size, 1000)
+                    val w = connection.bulkTransfer(epOut, setKeyCmd, setKeyCmd.size, USB_BULK_TIMEOUT_MS)
                     Log.d(TAG, "Sent SET_KEY ($w bytes)")
                     if (w < 0) {
                         return KeyResult.Error("SET_KEY schrijven mislukt")
                     }
 
-                    Thread.sleep(500)
+                    Thread.sleep(RESPONSE_WAIT_MS)
 
                     val okResponse = readResponse(connection, epIn, SET_KEY_TIMEOUT_MS)
                     Log.d(TAG, "SET_KEY response: ${okResponse.take(200)}")
diff --git a/android/app/src/main/java/com/eddy/atomrelay/UsbSerialTransport.kt b/android/app/src/main/java/com/eddy/atomrelay/UsbSerialTransport.kt
index 49dc1a0..96e718c 100644
--- a/android/app/src/main/java/com/eddy/atomrelay/UsbSerialTransport.kt
+++ b/android/app/src/main/java/com/eddy/atomrelay/UsbSerialTransport.kt
@@ -13,14 +13,18 @@ class UsbSerialTransport(
     private val epIn: UsbEndpoint
 ) : SerialTransport {
 
+    companion object {
+        private const val USB_TIMEOUT_MS = 5000
+    }
+
     override fun read(buffer: ByteArray, length: Int): Int {
-        val n = connection.bulkTransfer(epIn, buffer, length, 5000)
+        val n = connection.bulkTransfer(epIn, buffer, length, USB_TIMEOUT_MS)
         if (n < 0) return 0
         return n
     }
 
     override fun write(buffer: ByteArray, length: Int) {
-        val n = connection.bulkTransfer(epOut, buffer, length, 5000)
+        val n = connection.bulkTransfer(epOut, buffer, length, USB_TIMEOUT_MS)
         if (n < 0) throw IOException("USB write failed")
     }