Complex Device Drivers (CDD) in AUTOSAR

Example of Creating a Complex Device Driver (CDD) for a Custom Sensor

Creating a Complex Device Driver (CDD) for a custom sensor in an AUTOSAR-based system involves understanding the sensor’s hardware specifications, developing the necessary softw

are components to interact with the sensor, and integrating it within the broader AUTOSAR architecture. Below is a step-by-step breakdown of how you would develop a CDD for a custom sensor, including hardware, software, and system integration.

Step 1: Requirements Analysis

Before beginning development, it’s important to analyze the requirements for the custom sensor and the role of the CDD.

• Hardware Specifications:
  The custom sensor may communicate using protocols like I2C, SPI, or CAN. You will need to gather the sensor’s data sheet, which specifies its operating conditions, communication protocols, supported features (e.g., sampling rate, data resolution), and error handling mechanisms.
• Functional Requirements:
  • Data Acquisition: The sensor should provide real-time data such as temperature, pressure, or humidity, depending on its functionality.
  • Communication Protocol: The CDD will communicate with the sensor using a defined protocol (e.g., I2C) to send commands to initialize the sensor and read its output.
  • Error Handling: In case of communication failure, timeout, or sensor malfunction, the CDD should be capable of detecting the error and reporting it to the system.
• Non-Functional Requirements:
  The system may have real-time requirements to process the sensor data promptly. You may also need to consider power consumption, especially for battery-operated devices.
• Integration Requirements:
  The sensor data will need to be processed by the Application Layer, so you need to define the interface between the CDD and the AUTOSAR Runtime Environment (RTE), which facilitates data exchange between the sensor driver and higher-level software.

Step 2: Design the CDD Architecture

In this step, you will design the architecture of the CDD for the custom sensor.

• Driver Layers:
  The CDD will be designed with several layers:
  • Hardware Abstraction Layer (HAL): This layer abstracts the interaction with the sensor’s hardware. It handles low-level details like sending commands and receiving data from the sensor.
  • Driver Core: The core logic of the driver will manage the sensor’s initialization, data retrieval, and any communication protocols (e.g., SPI or I2C). This will also include any necessary interrupt handling.
  • Error Handling Layer: Detects and manages errors, such as communication timeouts or sensor malfunctions.
  • Diagnostic Layer: Implements diagnostic services to log and report errors, enabling fault detection and recovery.
• Communication Interfaces:
  The CDD will interact with the Basic Software (BSW) for various services, such as Communication Services (Com) for transmitting sensor data, Memory Services (Mem) for storing data, or OS Services for task management. The CDD will need to define APIs that allow the Application Layer to read sensor data.

Step 3: Configuration of the CDD

Now that the architecture is designed, the next step is configuring the CDD to fit the specific hardware and software environment.

• Configuration Parameters:
  The sensor may have parameters like:
  • I2C/SPI Configuration: Configure the bus speed, addressing mode, and protocol settings.
  • Interrupt Configuration: Define whether the sensor will trigger interrupts for data availability or if polling will be used.
  • Sampling Rate: Specify the frequency at which data should be collected from the sensor.
• AUTOSAR Configuration Tools:
  Use tools like AUTOSAR Builder or DaVinci Configurator to configure the BSW modules and to generate code for configuring the sensor driver.
• Parameterization:
  Parameters like the communication baud rate, sensor address, and error thresholds should be flexible so that they can be easily adapted to different sensor models or vehicle configurations.

Step 4: Implement the Driver Logic

With the architecture and configuration in place, it’s time to implement the CDD logic.

• Sensor Initialization:
  • The driver needs to initialize the sensor, configure communication settings (e.g., I2C), and set up any required hardware pins (e.g., chip select for SPI).

void Sensor_Init(void) {
    // Initialize I2C or SPI interface
    // Configure sensor settings (e.g., sampling rate, range)
    ConfigureSensor();
}

• Data Acquisition:
  The driver will need to read the sensor data in real-time. This could be done through polling or interrupt-based methods. If using I2C, the driver sends a read request to the sensor and fetches the sensor data.

uint16_t Sensor_ReadData(void) {
    uint16_t sensorData;
    // Send read command to sensor
    sensorData = I2C_Read(SENSOR_ADDRESS, DATA_REGISTER);
    return sensorData;
}

• Interrupt Handling:
  If the sensor supports interrupts for data ready or error conditions, the CDD will need to manage interrupts appropriately.

void Sensor_InterruptHandler(void) {
    // Handle interrupt to fetch sensor data
    uint16_t data = Sensor_ReadData();
    // Process the data
}

• Error Handling:
  The CDD should handle errors, such as communication failures or invalid data, and report these errors through the Diagnostic Layer.

void Sensor_ErrorHandler(void) {
    // Handle sensor communication or hardware errors
    ReportDiagnosticError(ERROR_SENSOR_COMMUNICATION);
}

Step 5: Integration with AUTOSAR Software Stack

Once the driver logic is implemented, the CDD needs to be integrated into the AUTOSAR software stack.

• Integration with RTE:
  The CDD will provide an interface to communicate with the Application Layer via the RTE. This allows the application to request sensor data or trigger specific driver functions.

void Sensor_ReadTask(void) {
    uint16_t sensorData = Sensor_ReadData();
    RTE_SendData(SENSOR_DATA, sensorData);
}

• Integration with BSW Modules:
  The CDD will interact with the Communication Services module to send data from the sensor to the Application Layer or other system components.

void Sensor_TransmitData(uint16_t sensorData) {
    Com_SendSignal(SENSOR_DATA_SIGNAL, sensorData);
}

• Testing Integration:
  After integrating the CDD, conduct system integration testing to ensure the driver works well with other BSW modules, such as the OS, Memory Management, or Communication Stack.

Step 6: Testing and Validation

The CDD for the custom sensor needs thorough testing to ensure it meets functional, non-functional, and safety requirements.

• Unit Testing: Test individual functions in isolation, such as sensor initialization, data acquisition, error handling, and communication protocols.
• Integration Testing: Ensure that the CDD works seamlessly with the RTE, other BSW modules, and the Application Layer. Simulate real-world conditions like high bus traffic or power fluctuations to ensure stability.
• Real-Time Testing: If the system has real-time requirements (e.g., sensor data must be processed within a specific time frame), conduct real-time testing to validate that the CDD meets these constraints.
• Fault Testing: Simulate sensor failure modes, such as communication timeouts or sensor malfunctions, and validate that the CDD handles errors correctly.

Step 7: Documentation

Document the implementation, configuration, and integration of the custom sensor driver.

• Code Documentation: Include detailed comments in the code to explain the logic, especially for complex interactions with the hardware or error handling routines.
• Configuration Documentation: Document all configuration parameters, such as communication settings, sample rates, and error thresholds.
• Testing Documentation: Record test cases, results, and known issues, providing a clear picture of the driver’s functionality and any limitations.

Step 8: Deployment and Maintenance

Once the CDD has passed testing, it’s ready for deployment.

• Deployment: Deploy the driver to the target hardware. This may involve compiling the driver for the target platform and ensuring that it works correctly in the final system.
• Maintenance: Periodically update the driver as needed, such as when the sensor firmware is updated or if new features are added. Additionally, monitor the performance of the sensor and driver in the production environment to identify and resolve any issues.