Скачать или смотреть Understanding the Dem_EventStatusType in Autosar: Handling the Gray Zone

Learn how to define and manage the `Dem_EventStatusType` in Autosar, especially when dealing with states that are neither prepassed nor prefailed in a diagnostic context.
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Understanding the Dem_EventStatusType in Autosar: Handling the Gray Zone

When working with the AUTOSAR specification, particularly the Diagnostic Event Manager (DEM), one can come across certain ambiguities, especially regarding the Dem_EventStatusType. The existing status options in the AUTOSAR standard include:

DEM_EVENT_STATUS_PASSED

DEM_EVENT_STATUS_FAILED

DEM_EVENT_STATUS_PREPASSED

DEM_EVENT_STATUS_PREFAILED

DEM_EVENT_STATUS_FDC_THRESHOLD_REACHED

However, there arises a significant gap: there's no designated status to represent a "Gray Zone"—a state that is neither clearly defined as prepassed nor prefailed. This gap can lead to confusion in diagnostic situations, complicating how event statuses are managed.

The Challenge: Representing the Gray Zone

In many scenarios, such as when monitoring sensor voltages, the need for a clear distinction between pass and fail states is crucial. When a situation arises where a value shifts from a prefailed status into a gray area—rather than a clearly passed state—it's essential to establish a method to represent this undefined state effectively.

Questions to Consider

Should the gray zone still be represented as prefailed or prepassed?

Is it viable to define a new status using reserved bits (for instance, from 0x05 to 0xFF)?

Can modifications to Dem_EventStatusType be undertaken, or are they restricted within specifications?

The Solution: Implementing a Monitoring Function

To resolve the ambiguity surrounding the gray zone, one effective approach is to use a monitoring function that assesses the voltage readings against defined thresholds. Below is a sample implementation that illustrates this method:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

Threshold Logic: The function Efx_HystCenterHalfDelta_u16_u8 checks whether the sensor value X lies outside defined threshold values. If X is above or below the specified center plus/minus halfDelta, it registers as a definitive state (either passed or failed).

State Management: It maintains a state that persists between calls, allowing for dynamic assessment as sensor values fluctuate.

Reporting Status: The mon_func function utilizes the reading from the hardware abstraction (in this case, IoHwAb_GetVoltageX) to determine if the current state is passed or failed based on the established gray zone logic.

Conclusion

By using this approach, you can effectively define states that avoid the ambiguity of the gray area by only reporting recognized passed or failed statuses when sensor readings are clearly outside the defined boundaries. While AUTOSAR doesn’t provide a built-in representation for the gray zone, effective monitoring and handling through software logic can bridge this gap, ensuring clear diagnostics in automotive applications.

Engaging with and potentially expanding on the AUTOSAR standard is vital for a more comprehensive diagnostic understanding. This not only improves functionality but also ensures a broader diagnostic insight across varied scenarios.