Introduction

Android Automotive OS (AAOS) provides a powerful, standardized interface for vehicle-specific hardware interactions through the Vehicle Hardware Abstraction Layer (VHAL). While VHAL offers a robust set of predefined properties, real-world automotive systems often require custom properties to expose unique sensor data, control mechanisms, or diagnostic information specific to a vehicle’s OEM implementation. Implementing these custom VHAL properties is one challenge; effectively debugging them when they don’t behave as expected is another. This article delves into advanced debugging techniques, specifically leveraging the familiar Android tools `dumpsys` and `logcat`, to inspect and monitor custom VHAL properties in Android Automotive.

Understanding the VHAL Architecture and Custom Properties

The VHAL is the bridge between the Android framework and the vehicle’s underlying hardware. It defines a set of properties, each identified by a unique ID, that represent vehicle systems like HVAC, sensors, or infotainment controls. Custom properties extend this functionality, allowing OEMs to integrate their unique hardware features seamlessly into the Android Automotive ecosystem.

VHAL Property Implementation Overview

At a high level, implementing a custom VHAL property involves:

1. Defining a unique property ID and its characteristics (read/write, type, change mode, min/max values) in a custom or extended `VehiclePropertyIds.h` header.
2. Implementing the property’s logic within the VHAL service (e.g., in a subclass of `VehicleHal.h` or its custom implementation). This involves handling `setProperty` and `getProperty` calls for your custom ID.
3. Registering the custom VHAL service with the Android system, typically via a Hardware Service (HALS) implementation.

Once implemented, the Android Car Service and applications interact with this property using the standard `CarPropertyManager` API, unaware that it’s a custom extension.

The Debugging Challenge for Custom Properties

Standard Android debugging tools like `adb shell getprop` are insufficient for VHAL properties, as VHAL operates within its own Binder interface. When a custom property isn’t behaving as expected – perhaps not reporting values, or not accepting commands – developers need methods to:

• Verify the property is registered and configured correctly by the VHAL service.
• Inspect its current state and values.
• Monitor its activity (gets and sets) in real-time.

This is where `dumpsys` and `logcat` become indispensable.

Leveraging `dumpsys` for VHAL State Inspection

`dumpsys` is a powerful Android shell command that provides diagnostic output for all running system services. For VHAL, it can give us a snapshot of the configured properties and their current values.

Inspecting the VHAL Service with `dumpsys`

To inspect the VHAL service, you’ll typically interact with the `android.hardware.automotive.vehicle` service. The command is:

adb shell dumpsys [email protected]::IVehicle/default

This command outputs a large amount of information, including all registered VHAL properties, their configurations, and their current values. To narrow down the output to your custom property, you can `grep` for its unique ID (e.g., `0x21000001` or `289408641`).

Example: Probing a Custom HVAC Air Quality Property

Let’s assume you’ve implemented a custom property `CUSTOM_HVAC_AIR_QUALITY_LEVEL` with ID `0x21000001` (decimal `289408641`). To check its status:

adb shell dumpsys [email protected]::IVehicle/default | grep -A 5

        
        
        

            

                
            
            

                
Android Mobile Specs & Compare Directory
                
Are you researching mobile hardware properties, processor SoCs, GPU chipsets, or RAM configurations? Access our complete specs catalog to compare up to 5 devices side-by-side!
                Compare Devices Specs →