Overview

Purpose

The EEPROM Emulation module provides an abstraction layer to emulate EEPROM functionality on STM32 Flash memory. It lets applications store and retrieve data persistently without requiring dedicated EEPROM hardware.

Key Features

The main features of EEPROM Emulation are:

  • Configurable emulation capacity: Number of variables and write cycles.

  • Algorithm selection: FLITF or NVM aligned with device constraints and performance.

  • Power-failure recovery: Restores a consistent state after reset, even if power is lost during a write.

  • Data integrity options: CRC for corruption detection and BCH-based ECC for bit error correction.

  • Pluggable interfaces: Ready-to-use and template drivers for Flash, CRC, and ECC.

  • Typed variable access: Persistent variables with fixed sizes (for example 8-bit, 16-bit, 32-bit).

  • Maintenance modes: Cleanup and wear-leveling can run in polling or interrupt-driven workflows.

Architecture

The following diagram illustrates the software components of the EEPROM Emulation utility and their interactions across the application, core, algorithms (FLITF/NVM), interfaces (Flash/CRC/ECC), STM32 HAL libraries, and hardware.

@startuml skinparam componentStyle rectangle title EEPROM Emulation Architecture Overview ' ========================= ' Application ' ========================= package "Application" { component APP as "User Application\n(firmware code)" } ' ========================= ' EEPROM Emulation ' ========================= package "EEPROM Emulation" { ' ------------------------- ' CORE MODULE ' ------------------------- package "CORE_MODULE" { component CORE as "core" package "ALGO" { component ALGO_FLITF as "Algo_FLITF" component ALGO_NVM as "Algo_NVM" } CORE --> ALGO_FLITF : selects / calls CORE --> ALGO_NVM : selects / calls } ' ------------------------- ' INTERFACES (Flash / CRC / ECC only) ' ------------------------- package "interface" { component ITF_FLASH_FLITF as "Flash interface\n(FLITF_EDATA)" component ITF_FLASH_NVM as "Flash interface\n(NVM_EDATA)" component ITF_CRC as "CRC interface" component ITF_ECC as "ECC interface\n(BCH)" } ' Liaisons ALGO -> interface ALGO_FLITF --> ITF_FLASH_FLITF : read / write / erase ALGO_NVM --> ITF_FLASH_NVM : read / write ALGO_FLITF --> ITF_CRC : integrity check ALGO_NVM --> ITF_CRC : integrity check ALGO_NVM --> ITF_ECC : error correction } ' ========================= ' System (HAL + HW) ' ========================= package "System" { component HAL_FLASH as "STM32 HAL_FLASH" component HAL_NVM as "STM32 HAL_NVM" component HAL_CRC as "STM32 HAL_CRC" component HW as "STM32_HW" HAL_FLASH --> HW : register access HAL_NVM --> HW : register access HAL_CRC --> HW : register access } ' ========================= ' Connections ' ========================= APP --> CORE : API calls ITF_FLASH_FLITF --> HAL_FLASH : driver calls ITF_FLASH_NVM --> HAL_NVM : driver calls ITF_CRC --> HAL_CRC : driver calls @enduml

Component Structure

Core ( eeprom_emul_core.c / eeprom_emul_core.h): Provides the main APIs for initialization, variable read/write, and maintenance. It manages the overall state and coordinates interactions between algorithms and interfaces.

Algorithms ( eeprom_algo_flitf.c / eeprom_algo_nvm.c): Implement the EEPROM Emulation algorithms, handling initialization, data read/write, and memory cleanup according to the selected method (FLITF or NVM).

The EEPROM Emulation utility supports two Flash memory technologies, selected according to the target STM32 device: FLITF and NVM. While the application always uses the same core API, the underlying algorithm differs because these technologies do not support updates in the same way.

With FLITF, a sector containing existing data must be erased before new data can be written to the same Flash location. The corresponding EEPROM emulation algorithm therefore manages updates through page states, page transfers, and cleanup operations.

With NVM, new data can be written to the same address without a prior erase operation. The corresponding EEPROM emulation algorithm stores variable values in dedicated records and can use the configured CRC and ECC services to preserve data integrity and support recovery after reset.

User configuration ( eeprom_emul_conf.h): Defines the main parameters for EEPROM Emulation, including Flash layout, number and size of variables, endurance options (number of write cycles), and enabled features (algorithms, CRC, ECC, maintenance mode).

Interfaces : Provide both ready-to-use implementations and customizable templates for Flash access, CRC calculation, and ECC encoding/decoding. The appropriate implementation can be selected or adapted to the target hardware and application needs.

Modules and Files

The following diagram illustrates the EEPROM Emulation module and its associated files.

@startuml top to bottom direction skinparam linetype ortho <style> componentDiagram { arrow { FontSize 8 } } </style> title EEPROM Emulation Modules Overview package "Application" { component APP as "User Application" } package "EEPROM Emulation" { package "Interfaces" as ITF_P { together { package "Flash" { component ITF_FLASH_H as "eeprom_itf_flash.h" component ITF_FLITF_EDATA as "eeprom_itfflash_flitf_edata.c" #DAE8FC component ITF_NVM_EDATA as "eeprom_itfflash_nvm_edata.c" #DAE8FC component ITF_FLASH_TPL as "eeprom_itfflash_template.c" #DAE8FC } package "CRC" { component ITF_CRC_H as "eeprom_itf_crc.h" component ITF_CRC as "eeprom_itfcrc_crc.c" #DAE8FC component ITF_CRC_TPL as "eeprom_itfcrc_template.c" #DAE8FC } package "ECC" { component ITF_ECC_H as "eeprom_itf_ecc.h" component ITF_ECC as "eeprom_itfecc_bch.c" #DAE8FC component ITF_ECC_TPL as "eeprom_itfecc_template.c" #DAE8FC } } } package "Algorithms" as ALGO_P { component ALGO_FLITF_C as "eeprom_algo_flitf.c" component ALGO_FLITF_H as "eeprom_algo_flitf.h" component ALGO_NVM_C as "eeprom_algo_nvm.c" component ALGO_NVM_H as "eeprom_algo_nvm.h" } package "Core" as CORE_P { component CORE_C as "eeprom_emul_core.c" component CORE_H as "eeprom_emul_core.h" component CORE_CONF as "eeprom_emul_conf.h" #DAE8FC } } APP --> CORE_C CORE_C ..> CORE_H : include CORE_H ..> CORE_CONF : include ALGO_FLITF_C ..> ALGO_FLITF_H : include ALGO_NVM_C ..> ALGO_NVM_H : include ITF_FLITF_EDATA ..> ITF_FLASH_H : include ITF_NVM_EDATA ..> ITF_FLASH_H : include ITF_FLASH_TPL ..> ITF_FLASH_H : include ITF_CRC ..> ITF_CRC_H : include ITF_CRC_TPL ..> ITF_CRC_H : include ITF_ECC ..> ITF_ECC_H : include ITF_ECC_TPL ..> ITF_ECC_H : include CORE_C ..> ALGO_FLITF_H : include CORE_C ..> ALGO_NVM_H : include CORE_C ..> ITF_FLASH_H : include CORE_C ..> ITF_CRC_H : include CORE_C ..> ITF_ECC_H : include @enduml