Alexa Device Integration in Mobile IoT App

Alexa Device Integration into Mobile IoT App

Alexa Smart Home — not one API, but three different paths depending on task. Managing smart home through Alexa Skills Kit (ASK) with Smart Home Skill — for third-party devices wanting voice command support. Alexa Mobile Accessory Kit (AMAK) — for Bluetooth accessories connected to Echo devices. Alexa Voice Service (AVS) Integration — embedding voice assistant directly in mobile app. Usually mobile development needs either Smart Home Skill or AVS.

Smart Home Skill: Device Control via Alexa

Working scheme: user says "Alexa, turn on light," Alexa Smart Home sends directive to developer Lambda function, Lambda controls real device via backend or directly. Mobile app in this scheme — configuration and authorization point, not control.

Account Linking — key step. User authorizes Alexa via OAuth 2.0 on developer server. Alexa then gets access token and passes it with each directive:

{
  "directive": {
    "header": {
      "namespace": "Alexa.PowerController",
      "name": "TurnOn"
    },
    "endpoint": {
      "endpointId": "device-001",
      "scope": {
        "type": "BearerToken",
        "token": "user-access-token"
      }
    }
  }
}

Lambda processes directive and responds. For successful Alexa Smart Home Certification Response must arrive within 8 seconds — hard deadline.

Mobile app opens WebView for Account Linking or uses Custom URL Scheme for OAuth redirect:

// iOS: handle OAuth callback
func scene(_ scene: UIScene, openURLContexts URLContexts: Set<UIOpenURLContext>) {
    guard let url = URLContexts.first?.url,
          url.scheme == "myapp",
          url.host == "alexa-auth" else { return }

    let components = URLComponents(url: url, resolvingAgainstBaseURL: false)
    let code = components?.queryItems?.first(where: { $0.name == "code" })?.value
    // Exchange code for token via backend
}

AVS Integration: Alexa in Mobile App

Alexa Voice Service lets embed voice assistant in app. SDK available for Android via com.amazon.alexa:avs-device-sdk-android (deprecated) or via Alexa Auto SDK for automotive apps. Official path for mobile — AVS API directly via HTTP/2:

POST https://avs-alexa-eu.amazon.com/v20160207/events
Content-Type: multipart/form-data; boundary=boundary
Authorization: Bearer {access_token}

--boundary
Content-Disposition: form-data; name="metadata"
Content-Type: application/json

{
  "event": {
    "header": {
      "namespace": "SpeechRecognizer",
      "name": "Recognize",
      "messageId": "uuid"
    },
    "payload": {
      "profile": "CLOSE_TALK",
      "format": "AUDIO_L16_RATE_16000_CHANNELS_1"
    }
  }
}
--boundary
Content-Disposition: form-data; name="audio"
Content-Type: application/octet-stream

[PCM audio data 16kHz, 16-bit mono]
--boundary--

AVS responds with multipart response containing directives and TTS audio. Audio stream must be captured via AVAudioEngine on iOS or AudioRecord on Android with 320-byte buffer (20ms) for minimal latency.

In practice pure AVS API integration takes longer than appears: dialog state management (Dialog Request ID), downstream directive handling via long-lived HTTP/2 (Downchannel), wake word support — separate task each.

Alexa for Android: APL and Visual Responses

Alexa Presentation Language (APL) lets display visual cards on screened Echo devices and apps with APL renderer. Android SDK for APL:

implementation("com.amazon.alexa:apl-android-sdk:2024.1")

APL document — JSON describing interface. Renderer displays it without writing native code per platform.

Most common AVS integration problem — microphone management in background. Android 10+ requires FOREGROUND_SERVICE with microphone type for audio capture when app not foreground. Without <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MICROPHONE"/> app crashes with SecurityException on service start.

Smart Home Skill Publication

Certify Alexa Smart Home Skill via Alexa Developer Console. Main requirements: Account Linking via HTTPS, correct Response for all declared Capability Interfaces, handle Alexa.Discovery request — return user's device list.

Typical certification rejection reason — incorrect ChangeReport on state change not from Alexa command. If user turned on light with physical switch, Smart Home Skill should send ChangeReport via Alexa Event Gateway.

Timeline: Account Linking and basic Smart Home Skill — 2-3 weeks. Full implementation with AVS, APL and multiple Capability Interfaces — 5-7 weeks. Cost calculated after analyzing devices and scenarios.