Fee - Flash EEPROM Emulation - AUTOSAR Classic BSW

Fee Sector Layout & Wear Leveling

Fee Dual-Sector Wear Leveling

  Physical Flash Sector 0 (256 KB)        Physical Flash Sector 1 (256 KB)
  ┌──────────────────────────────────┐    ┌────────────────────────────────┐
  │ Block HDR | OdometerData  (4B)   │    │ (empty — erased)               │
  │ Block HDR | CalibData     (32B)  │    │                                │
  │ Block HDR | FaultCounter  (2B)   │    │ (copy target when Sector 0 80%)│
  │ (sector ACTIVE)                  │    │                                │
  └──────────────────────────────────┘    └────────────────────────────────┘
  When Sector 0 is 80% full:
    Fee copies valid blocks to Sector 1 → marks Sector 1 ACTIVE → erases Sector 0

💡 FeeBlockSize

FeeBlockSize must be a multiple of the flash page size (typically 4 or 8 bytes on NOR flash). Misalignment causes Fee_Write to silently write to a partial page, resulting in data corruption on subsequent reads.

Block Header Status Bytes

Status	Value	Description
VALID	0xA5 (magic)	Block written successfully; CRC verified
INVALID	0x5A	Block explicitly invalidated (Fee_InvalidateBlock called)
INCONSISTENT	0xFF…0xFF	Power loss during write — partially written; detected via CRC mismatch

Fee Operations

CFee_Usage.c

/* Fee_Read: must poll Fee_MainFunction + check Fee_GetJobResult */
uint8 readBuf[4];
Fee_Read(FEE_BLOCK_ID_ODOMETER, 0, readBuf, 4);
while (Fee_GetJobResult() == MEMIF_JOB_PENDING) { Fee_MainFunction(); }
if (Fee_GetJobResult() == MEMIF_JOB_OK) { /* data ready */ }

/* Fee_Write: queues write; Fee_MainFunction processes it */
uint8 writeBuf[4] = {0x00, 0x0F, 0x42, 0x40};
Fee_Write(FEE_BLOCK_ID_ODOMETER, writeBuf);

Garbage Collection & Sleep Impact

Fee GC copies live blocks between sectors and erases the old sector. A full NOR flash sector erase takes 200–800 ms depending on the device.

⚠️ GC During Sleep Entry

If GC starts during BswM sleep entry, the erase can block the OS for up to 800 ms, preventing ECU sleep on time. Mitigate by: (1) setting GC trigger threshold to 60% (not 80%); (2) configuring BswM to call Fee_ForceSwapActive if GC is pending at shutdown.

Summary

Fee's dual-sector wear leveling is transparent to NvM via the MemIf abstraction. Correct FeeBlockSize alignment, GC threshold calibration, and sleep timing analysis are the critical Fee configuration decisions for production.

🔬 Deep Dive — Core Concepts Expanded

This section builds on the foundational concepts covered above with additional technical depth, edge cases, and configuration nuances that separate competent engineers from experts. When working on production ECU projects, the details covered here are the ones most commonly responsible for integration delays and late-phase defects.

Key principles to reinforce:

Configuration over coding: In AUTOSAR and automotive middleware environments, correctness is largely determined by ARXML configuration, not application code. A correctly implemented algorithm can produce wrong results due to a single misconfigured parameter.
Traceability as a first-class concern: Every configuration decision should be traceable to a requirement, safety goal, or architecture decision. Undocumented configuration choices are a common source of regression defects when ECUs are updated.
Cross-module dependencies: In tightly integrated automotive software stacks, changing one module's configuration often requires corresponding updates in dependent modules. Always perform a dependency impact analysis before submitting configuration changes.

🏭 How This Topic Appears in Production Projects

Project integration phase: The concepts covered in this lesson are most commonly encountered during ECU integration testing — when multiple software components from different teams are combined for the first time. Issues that were invisible in unit tests frequently surface at this stage.
Supplier/OEM interface: This is a topic that frequently appears in technical discussions between Tier-1 ECU suppliers and OEM system integrators. Engineers who can speak fluently about these details earn credibility and are often brought into critical design review meetings.
Automotive tool ecosystem: Vector CANoe/CANalyzer, dSPACE tools, and ETAS INCA are the standard tools used to validate and measure the correct behaviour of the systems described in this lesson. Familiarity with these tools alongside the conceptual knowledge dramatically accelerates debugging in real projects.

⚠️ Common Mistakes and How to Avoid Them

Assuming default configuration is correct: Automotive software tools ship with default configurations that are designed to compile and link, not to meet project-specific requirements. Every configuration parameter needs to be consciously set. 'It compiled' is not the same as 'it is correctly configured'.
Skipping documentation of configuration rationale: In a 3-year ECU project with team turnover, undocumented configuration choices become tribal knowledge that disappears when engineers leave. Document why a parameter is set to a specific value, not just what it is set to.
Testing only the happy path: Automotive ECUs must behave correctly under fault conditions, voltage variations, and communication errors. Always test the error handling paths as rigorously as the nominal operation. Many production escapes originate in untested error branches.
Version mismatches between teams: In a multi-team project, the BSW team, SWC team, and system integration team may use different versions of the same ARXML file. Version management of all ARXML files in a shared repository is mandatory, not optional.

📊 Industry Note

Engineers who master both the theoretical concepts and the practical toolchain skills covered in this course are among the most sought-after professionals in the automotive software industry. The combination of AUTOSAR standards knowledge, safety engineering understanding, and hands-on configuration experience commands premium salaries at OEMs and Tier-1 suppliers globally.