eeprom_stm32: implement high density wear leveling (#12567)

* eeprom_stm32: implement wear leveling
Update EECONFIG_MAGIC_NUMBER
eeprom_stm32: check emulated eeprom size is large enough
* eeprom_stm32: Increasing simulated EEPROM density on stm32
* Adding utility script to decode emulated eeprom
* Adding unit tests
* Applying qmk cformat changes
* cleaned up flash mocking
* Fix for stm32eeprom_parser.py checking via signature with wrong base
* Fix for nk65 keyboard

Co-authored-by: Ilya Zhuravlev <whatever@xyz.is>
Co-authored-by: zvecr <git@zvecr.com>

12 files changed, 1529 insertions, 177 deletions

diff --git a/build_test.mk b/build_test.mk
index b6b8782174..037577bf90 100644
--- a/build_test.mk
+++ b/build_test.mk
@@ -56,6 +56,7 @@ include $(TMK_PATH)/common.mk
 include $(QUANTUM_PATH)/debounce/tests/rules.mk
 include $(QUANTUM_PATH)/sequencer/tests/rules.mk
 include $(QUANTUM_PATH)/serial_link/tests/rules.mk
+include $(TMK_PATH)/common/test/rules.mk
 ifneq ($(filter $(FULL_TESTS),$(TEST)),)
 include build_full_test.mk
 endif
diff --git a/keyboards/nk65/config.h b/keyboards/nk65/config.h
index fa14e9ffbf..a178307cc0 100755
--- a/keyboards/nk65/config.h
+++ b/keyboards/nk65/config.h
@@ -148,6 +148,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
  * both 128kb and 256kb versions of F303.
  * Register 0x1FFFF7CC holds the size of the flash memory.
  */
+#ifndef FLASHSIZE_BASE
+#  define FLASHSIZE_BASE ((uint32_t)0x1FFFF7CCU) /*!< FLASH Size register base address */
+#endif
 #define EEPROM_START_ADDRESS
 #define FEE_MCU_FLASH_SIZE                              \
 ({                                                      \
diff --git a/quantum/eeconfig.h b/quantum/eeconfig.h
index a88071729d..bd39971b2c 100644
--- a/quantum/eeconfig.h
+++ b/quantum/eeconfig.h
@@ -21,7 +21,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <stdbool.h>
 
 #ifndef EECONFIG_MAGIC_NUMBER
-#    define EECONFIG_MAGIC_NUMBER (uint16_t)0xFEEA  // When changing, decrement this value to avoid future re-init issues
+#    define EECONFIG_MAGIC_NUMBER (uint16_t)0xFEE9  // When changing, decrement this value to avoid future re-init issues
 #endif
 #define EECONFIG_MAGIC_NUMBER_OFF (uint16_t)0xFFFF
 
diff --git a/testlist.mk b/testlist.mk
index d256f4c815..b66b93d295 100644
--- a/testlist.mk
+++ b/testlist.mk
@@ -4,6 +4,7 @@ FULL_TESTS := $(TEST_LIST)
 include $(ROOT_DIR)/quantum/debounce/tests/testlist.mk
 include $(ROOT_DIR)/quantum/sequencer/tests/testlist.mk
 include $(ROOT_DIR)/quantum/serial_link/tests/testlist.mk
+include $(ROOT_DIR)/tmk_core/common/test/testlist.mk
 
 define VALIDATE_TEST_LIST
     ifneq ($1,)
diff --git a/tmk_core/common/chibios/eeprom_stm32.c b/tmk_core/common/chibios/eeprom_stm32.c
index ea51989728..5bf852fde1 100644
--- a/tmk_core/common/chibios/eeprom_stm32.c
+++ b/tmk_core/common/chibios/eeprom_stm32.c
@@ -14,185 +14,751 @@
  * Artur F.
  *
  * Modifications for QMK and STM32F303 by Yiancar
+ * Modifications to add flash wear leveling by Ilya Zhuravlev
+ * Modifications to increase flash density by Don Kjer
  */
 
 #include <stdio.h>
-#include <string.h>
+#include <stdbool.h>
+#include "debug.h"
 #include "eeprom_stm32.h"
-/*****************************************************************************
- * Allows to use the internal flash to store non volatile data. To initialize
- * the functionality use the EEPROM_Init() function. Be sure that by reprogramming
- * of the controller just affected pages will be deleted. In other case the non
- * volatile data will be lost.
- ******************************************************************************/
+#include "flash_stm32.h"
+
+/*
+ * We emulate eeprom by writing a snapshot compacted view of eeprom contents,
+ * followed by a write log of any change since that snapshot:
+ *
+ * === SIMULATED EEPROM CONTENTS ===
+ *
+ * ┌─ Compacted ┬ Write Log ─┐
+ * │............│[BYTE][BYTE]│
+ * │FFFF....FFFF│[WRD0][WRD1]│
+ * │FFFFFFFFFFFF│[WORD][NEXT]│
+ * │....FFFFFFFF│[BYTE][WRD0]│
+ * ├────────────┼────────────┤
+ * └──PAGE_BASE │            │
+ *    PAGE_LAST─┴─WRITE_BASE │
+ *                WRITE_LAST ┘
+ *
+ * Compacted contents are the 1's complement of the actual EEPROM contents.
+ * e.g. An 'FFFF' represents a '0000' value.
+ *
+ * The size of the 'compacted' area is equal to the size of the 'emulated' eeprom.
+ * The size of the compacted-area and write log are configurable, and the combined
+ * size of Compacted + WriteLog is a multiple FEE_PAGE_SIZE, which is MCU dependent.
+ * Simulated Eeprom contents are located at the end of available flash space.
+ *
+ * The following configuration defines can be set:
+ *
+ * FEE_DENSITY_PAGES   # Total number of pages to use for eeprom simulation (Compact + Write log)
+ * FEE_DENSITY_BYTES   # Size of simulated eeprom. (Defaults to half the space allocated by FEE_DENSITY_PAGES)
+ * NOTE: The current implementation does not include page swapping,
+ * and FEE_DENSITY_BYTES will consume that amount of RAM as a cached view of actual EEPROM contents.
+ *
+ * The maximum size of FEE_DENSITY_BYTES is currently 16384. The write log size equals
+ * FEE_DENSITY_PAGES * FEE_PAGE_SIZE - FEE_DENSITY_BYTES.
+ * The larger the write log, the less frequently the compacted area needs to be rewritten.
+ *
+ *
+ * *** General Algorithm ***
+ *
+ * During initialization:
+ * The contents of the Compacted-flash area are loaded and the 1's complement value
+ * is cached into memory (e.g. 0xFFFF in Flash represents 0x0000 in cache).
+ * Write log entries are processed until a 0xFFFF is reached.
+ * Each log entry updates a byte or word in the cache.
+ *
+ * During reads:
+ * EEPROM contents are given back directly from the cache in memory.
+ *
+ * During writes:
+ * The contents of the cache is updated first.
+ * If the Compacted-flash area corresponding to the write address is unprogrammed, the 1's complement of the value is written directly into Compacted-flash
+ * Otherwise:
+ * If the write log is full, erase both the Compacted-flash area and the Write log, then write cached contents to the Compacted-flash area.
+ * Otherwise a Write log entry is constructed and appended to the next free position in the Write log.
+ *
+ *
+ * *** Write Log Structure ***
+ *
+ * Write log entries allow for optimized byte writes to addresses below 128. Writing 0 or 1 words are also optimized when word-aligned.
+ *
+ * === WRITE LOG ENTRY FORMATS ===
+ *
+ * ╔═══ Byte-Entry ══╗
+ * ║0XXXXXXX║YYYYYYYY║
+ * ║ └──┬──┘║└──┬───┘║
+ * ║ Address║ Value  ║
+ * ╚════════╩════════╝
+ * 0 <= Address < 0x80 (128)
+ *
+ * ╔ Word-Encoded 0 ╗
+ * ║100XXXXXXXXXXXXX║
+ * ║  │└─────┬─────┘║
+ * ║  │Address >> 1 ║
+ * ║  └── Value: 0  ║
+ * ╚════════════════╝
+ * 0 <= Address <= 0x3FFE (16382)
+ *
+ * ╔ Word-Encoded 1 ╗
+ * ║101XXXXXXXXXXXXX║
+ * ║  │└─────┬─────┘║
+ * ║  │Address >> 1 ║
+ * ║  └── Value: 1  ║
+ * ╚════════════════╝
+ * 0 <= Address <= 0x3FFE (16382)
+ *
+ * ╔═══ Reserved ═══╗
+ * ║110XXXXXXXXXXXXX║
+ * ╚════════════════╝
+ *
+ * ╔═══════════ Word-Next ═══════════╗
+ * ║111XXXXXXXXXXXXX║YYYYYYYYYYYYYYYY║
+ * ║   └─────┬─────┘║└───────┬──────┘║
+ * ║(Address-128)>>1║     ~Value     ║
+ * ╚════════════════╩════════════════╝
+ * (  0 <= Address <  0x0080 (128): Reserved)
+ * 0x80 <= Address <= 0x3FFE (16382)
+ *
+ * Write Log entry ranges:
+ * 0x0000 ... 0x7FFF - Byte-Entry;     address is (Entry & 0x7F00) >> 4; value is (Entry & 0xFF)
+ * 0x8000 ... 0x9FFF - Word-Encoded 0; address is (Entry & 0x1FFF) << 1; value is 0
+ * 0xA000 ... 0xBFFF - Word-Encoded 1; address is (Entry & 0x1FFF) << 1; value is 1
+ * 0xC000 ... 0xDFFF - Reserved
+ * 0xE000 ... 0xFFBF - Word-Next;      address is (Entry & 0x1FFF) << 1 + 0x80; value is ~(Next_Entry)
+ * 0xFFC0 ... 0xFFFE - Reserved
+ * 0xFFFF            - Unprogrammed
+ *
+ */
 
-/* Private macro -------------------------------------------------------------*/
-/* Private variables ---------------------------------------------------------*/
-/* Functions -----------------------------------------------------------------*/
+/* These bits are used for optimizing encoding of bytes, 0 and 1 */
+#define FEE_WORD_ENCODING 0x8000
+#define FEE_VALUE_NEXT 0x6000
+#define FEE_VALUE_RESERVED 0x4000
+#define FEE_VALUE_ENCODED 0x2000
+#define FEE_BYTE_RANGE 0x80
+
+// HACK ALERT. This definition may not match your processor
+// To Do. Work out correct value for EEPROM_PAGE_SIZE on the STM32F103CT6 etc
+#if defined(EEPROM_EMU_STM32F303xC)
+#    define MCU_STM32F303CC
+#elif defined(EEPROM_EMU_STM32F103xB)
+#    define MCU_STM32F103RB
+#elif defined(EEPROM_EMU_STM32F072xB)
+#    define MCU_STM32F072CB
+#elif defined(EEPROM_EMU_STM32F042x6)
+#    define MCU_STM32F042K6
+#elif !defined(FEE_PAGE_SIZE) || !defined(FEE_DENSITY_PAGES) || !defined(FEE_MCU_FLASH_SIZE)
+#    error "not implemented."
+#endif
+
+#if !defined(FEE_PAGE_SIZE) || !defined(FEE_DENSITY_PAGES)
+#    if defined(MCU_STM32F103RB) || defined(MCU_STM32F042K6)
+#        ifndef FEE_PAGE_SIZE
+#            define FEE_PAGE_SIZE 0x400  // Page size = 1KByte
+#        endif
+#        ifndef FEE_DENSITY_PAGES
+#            define FEE_DENSITY_PAGES 2  // How many pages are used
+#        endif
+#    elif defined(MCU_STM32F103ZE) || defined(MCU_STM32F103RE) || defined(MCU_STM32F103RD) || defined(MCU_STM32F303CC) || defined(MCU_STM32F072CB)
+#        ifndef FEE_PAGE_SIZE
+#            define FEE_PAGE_SIZE 0x800  // Page size = 2KByte
+#        endif
+#        ifndef FEE_DENSITY_PAGES
+#            define FEE_DENSITY_PAGES 4  // How many pages are used
+#        endif
+#    else
+#        error "No MCU type specified. Add something like -DMCU_STM32F103RB to your compiler arguments (probably in a Makefile)."
+#    endif
+#endif
+
+#ifndef FEE_MCU_FLASH_SIZE
+#    if defined(MCU_STM32F103RB) || defined(MCU_STM32F072CB)
+#        define FEE_MCU_FLASH_SIZE 128  // Size in Kb
+#    elif defined(MCU_STM32F042K6)
+#        define FEE_MCU_FLASH_SIZE 32  // Size in Kb
+#    elif defined(MCU_STM32F103ZE) || defined(MCU_STM32F103RE)
+#        define FEE_MCU_FLASH_SIZE 512  // Size in Kb
+#    elif defined(MCU_STM32F103RD)
+#        define FEE_MCU_FLASH_SIZE 384  // Size in Kb
+#    elif defined(MCU_STM32F303CC)
+#        define FEE_MCU_FLASH_SIZE 256  // Size in Kb
+#    else
+#        error "No MCU type specified. Add something like -DMCU_STM32F103RB to your compiler arguments (probably in a Makefile)."
+#    endif
+#endif
+
+#define FEE_XSTR(x) FEE_STR(x)
+#define FEE_STR(x) #x
+
+/* Size of combined compacted eeprom and write log pages */
+#define FEE_DENSITY_MAX_SIZE (FEE_DENSITY_PAGES * FEE_PAGE_SIZE)
+/* Addressable range 16KByte: 0 <-> (0x1FFF << 1) */
+#define FEE_ADDRESS_MAX_SIZE 0x4000
+
+#ifndef EEPROM_START_ADDRESS /* *TODO: Get rid of this check */
+#    if FEE_DENSITY_MAX_SIZE > (FEE_MCU_FLASH_SIZE * 1024)
+#        pragma message FEE_XSTR(FEE_DENSITY_MAX_SIZE) " > " FEE_XSTR(FEE_MCU_FLASH_SIZE * 1024)
+#        error emulated eeprom: FEE_DENSITY_PAGES is greater than available flash size
+#    endif
+#endif
+
+/* Size of emulated eeprom */
+#ifdef FEE_DENSITY_BYTES
+#    if (FEE_DENSITY_BYTES > FEE_DENSITY_MAX_SIZE)
+#        pragma message FEE_XSTR(FEE_DENSITY_BYTES) " > " FEE_XSTR(FEE_DENSITY_MAX_SIZE)
+#        error emulated eeprom: FEE_DENSITY_BYTES exceeds FEE_DENSITY_MAX_SIZE
+#    endif
+#    if (FEE_DENSITY_BYTES == FEE_DENSITY_MAX_SIZE)
+#        pragma message FEE_XSTR(FEE_DENSITY_BYTES) " == " FEE_XSTR(FEE_DENSITY_MAX_SIZE)
+#        warning emulated eeprom: FEE_DENSITY_BYTES leaves no room for a write log.  This will greatly increase the flash wear rate!
+#    endif
+#    if FEE_DENSITY_BYTES > FEE_ADDRESS_MAX_SIZE
+#        pragma message FEE_XSTR(FEE_DENSITY_BYTES) " > " FEE_XSTR(FEE_ADDRESS_MAX_SIZE)
+#        error emulated eeprom: FEE_DENSITY_BYTES is greater than FEE_ADDRESS_MAX_SIZE allows
+#    endif
+#    if ((FEE_DENSITY_BYTES) % 2) == 1
+#        error emulated eeprom: FEE_DENSITY_BYTES must be even
+#    endif
+#else
+/* Default to half of allocated space used for emulated eeprom, half for write log */
+#    define FEE_DENSITY_BYTES (FEE_DENSITY_PAGES * FEE_PAGE_SIZE / 2)
+#endif
+
+/* Size of write log */
+#define FEE_WRITE_LOG_BYTES (FEE_DENSITY_PAGES * FEE_PAGE_SIZE - FEE_DENSITY_BYTES)
+
+/* Start of the emulated eeprom compacted flash area */
+#ifndef FEE_FLASH_BASE
+#    define FEE_FLASH_BASE 0x8000000
+#endif
+#define FEE_PAGE_BASE_ADDRESS ((uintptr_t)(FEE_FLASH_BASE) + FEE_MCU_FLASH_SIZE * 1024 - FEE_WRITE_LOG_BYTES - FEE_DENSITY_BYTES)
+/* End of the emulated eeprom compacted flash area */
+#define FEE_PAGE_LAST_ADDRESS (FEE_PAGE_BASE_ADDRESS + FEE_DENSITY_BYTES)
+/* Start of the emulated eeprom write log */
+#define FEE_WRITE_LOG_BASE_ADDRESS FEE_PAGE_LAST_ADDRESS
+/* End of the emulated eeprom write log */
+#define FEE_WRITE_LOG_LAST_ADDRESS (FEE_WRITE_LOG_BASE_ADDRESS + FEE_WRITE_LOG_BYTES)
+
+/* Flash word value after erase */
+#define FEE_EMPTY_WORD ((uint16_t)0xFFFF)
+
+#if defined(DYNAMIC_KEYMAP_EEPROM_MAX_ADDR) && (DYNAMIC_KEYMAP_EEPROM_MAX_ADDR >= FEE_DENSITY_BYTES)
+#    error emulated eeprom: DYNAMIC_KEYMAP_EEPROM_MAX_ADDR is greater than the FEE_DENSITY_BYTES available
+#endif
+
+/* In-memory contents of emulated eeprom for faster access */
+/* *TODO: Implement page swapping */
+static uint16_t WordBuf[FEE_DENSITY_BYTES / 2];
+static uint8_t *DataBuf = (uint8_t *)WordBuf;
+
+/* Pointer to the first available slot within the write log */
+static uint16_t *empty_slot;
+
+// #define DEBUG_EEPROM_OUTPUT
+
+/*
+ * Debug print utils
+ */
+
+#if defined(DEBUG_EEPROM_OUTPUT)
+
+#    define debug_eeprom debug_enable
+#    define eeprom_println(s) println(s)
+#    define eeprom_printf(fmt, ...) xprintf(fmt, ##__VA_ARGS__);
+
+#else /* NO_DEBUG */
+
+#    define debug_eeprom false
+#    define eeprom_println(s)
+#    define eeprom_printf(fmt, ...)
+
+#endif /* NO_DEBUG */
+
+void print_eeprom(void) {
+#ifndef NO_DEBUG
+    int empty_rows = 0;
+    for (uint16_t i = 0; i < FEE_DENSITY_BYTES; i++) {
+        if (i % 16 == 0) {
+            if (i >= FEE_DENSITY_BYTES - 16) {
+                /* Make sure we display the last row */
+                empty_rows = 0;
+            }
+            /* Check if this row is uninitialized */
+            ++empty_rows;
+            for (uint16_t j = 0; j < 16; j++) {
+                if (DataBuf[i + j]) {
+                    empty_rows = 0;
+                    break;
+                }
+            }
+            if (empty_rows > 1) {
+                /* Repeat empty row */
+                if (empty_rows == 2) {
+                    /* Only display the first repeat empty row */
+                    println("*");
+                }
+                i += 15;
+                continue;
+            }
+            xprintf("%04x", i);
+        }
+        if (i % 8 == 0) print(" ");
+
+        xprintf(" %02x", DataBuf[i]);
+        if ((i + 1) % 16 == 0) {
+            println("");
+        }
+    }
+#endif
+}
 
-uint8_t DataBuf[FEE_PAGE_SIZE];
-/*****************************************************************************
- *  Delete Flash Space used for user Data, deletes the whole space between
- *  RW_PAGE_BASE_ADDRESS and the last uC Flash Page
- ******************************************************************************/
 uint16_t EEPROM_Init(void) {
-    // unlock flash
-    FLASH_Unlock();
+    /* Load emulated eeprom contents from compacted flash into memory */
+    uint16_t *src  = (uint16_t *)FEE_PAGE_BASE_ADDRESS;
+    uint16_t *dest = (uint16_t *)DataBuf;
+    for (; src < (uint16_t *)FEE_PAGE_LAST_ADDRESS; ++src, ++dest) {
+        *dest = ~*src;
+    }
+
+    if (debug_eeprom) {
+        println("EEPROM_Init Compacted Pages:");
+        print_eeprom();
+        println("EEPROM_Init Write Log:");
+    }
+
+    /* Replay write log */
+    uint16_t *log_addr;
+    for (log_addr = (uint16_t *)FEE_WRITE_LOG_BASE_ADDRESS; log_addr < (uint16_t *)FEE_WRITE_LOG_LAST_ADDRESS; ++log_addr) {
+        uint16_t address = *log_addr;
+        if (address == FEE_EMPTY_WORD) {
+            break;
+        }
+        /* Check for lowest 128-bytes optimization */
+        if (!(address & FEE_WORD_ENCODING)) {
+            uint8_t bvalue = (uint8_t)address;
+            address >>= 8;
+            DataBuf[address] = bvalue;
+            eeprom_printf("DataBuf[0x%02x] = 0x%02x;\n", address, bvalue);
+        } else {
+            uint16_t wvalue;
+            /* Check if value is in next word */
+            if ((address & FEE_VALUE_NEXT) == FEE_VALUE_NEXT) {
+                /* Read value from next word */
+                if (++log_addr >= (uint16_t *)FEE_WRITE_LOG_LAST_ADDRESS) {
+                    break;
+                }
+                wvalue = ~*log_addr;
+                if (!wvalue) {
+                    eeprom_printf("Incomplete write at log_addr: 0x%04x;\n", (uint32_t)log_addr);
+                    /* Possibly incomplete write.  Ignore and continue */
+                    continue;
+                }
+                address &= 0x1FFF;
+                address <<= 1;
+                /* Writes to addresses less than 128 are byte log entries */
+                address += FEE_BYTE_RANGE;
+            } else {
+                /* Reserved for future use */
+                if (address & FEE_VALUE_RESERVED) {
+                    eeprom_printf("Reserved encoded value at log_addr: 0x%04x;\n", (uint32_t)log_addr);
+                    continue;
+                }
+                /* Optimization for 0 or 1 values. */
+                wvalue = (address & FEE_VALUE_ENCODED) >> 13;
+                address &= 0x1FFF;
+                address <<= 1;
+            }
+            if (address < FEE_DENSITY_BYTES) {
+                eeprom_printf("DataBuf[0x%04x] = 0x%04x;\n", address, wvalue);
+                *(uint16_t *)(&DataBuf[address]) = wvalue;
+            } else {
+                eeprom_printf("DataBuf[0x%04x] cannot be set to 0x%04x [BAD ADDRESS]\n", address, wvalue);
+            }
+        }
+    }
 
-    // Clear Flags
-    // FLASH_ClearFlag(FLASH_SR_EOP|FLASH_SR_PGERR|FLASH_SR_WRPERR);
+    empty_slot = log_addr;
+
+    if (debug_eeprom) {
+        println("EEPROM_Init Final DataBuf:");
+        print_eeprom();
+    }
 
     return FEE_DENSITY_BYTES;
 }
-/*****************************************************************************
- *  Erase the whole reserved Flash Space used for user Data
- ******************************************************************************/
-void EEPROM_Erase(void) {
-    int page_num = 0;
 
-    // delete all pages from specified start page to the last page
-    do {
+/* Clear flash contents (doesn't touch in-memory DataBuf) */
+static void eeprom_clear(void) {
+    FLASH_Unlock();
+
+    for (uint16_t page_num = 0; page_num < FEE_DENSITY_PAGES; ++page_num) {
+        eeprom_printf("FLASH_ErasePage(0x%04x)\n", (uint32_t)(FEE_PAGE_BASE_ADDRESS + (page_num * FEE_PAGE_SIZE)));
         FLASH_ErasePage(FEE_PAGE_BASE_ADDRESS + (page_num * FEE_PAGE_SIZE));
-        page_num++;
-    } while (page_num < FEE_DENSITY_PAGES);
+    }
+
+    FLASH_Lock();
+
+    empty_slot = (uint16_t *)FEE_WRITE_LOG_BASE_ADDRESS;
+    eeprom_printf("eeprom_clear empty_slot: 0x%08x\n", (uint32_t)empty_slot);
 }
-/*****************************************************************************
- *  Writes once data byte to flash on specified address. If a byte is already
- *  written, the whole page must be copied to a buffer, the byte changed and
- *  the manipulated buffer written after PageErase.
- *******************************************************************************/
-uint16_t EEPROM_WriteDataByte(uint16_t Address, uint8_t DataByte) {
-    FLASH_Status FlashStatus = FLASH_COMPLETE;
 
-    uint32_t page;
-    int      i;
+/* Erase emulated eeprom */
+void EEPROM_Erase(void) {
+    eeprom_println("EEPROM_Erase");
+    /* Erase compacted pages and write log */
+    eeprom_clear();
+    /* re-initialize to reset DataBuf */
+    EEPROM_Init();
+}
 
-    // exit if desired address is above the limit (e.G. under 2048 Bytes for 4 pages)
-    if (Address > FEE_DENSITY_BYTES) {
-        return 0;
+/* Compact write log */
+static uint8_t eeprom_compact(void) {
+    /* Erase compacted pages and write log */
+    eeprom_clear();
+
+    FLASH_Unlock();
+
+    FLASH_Status final_status = FLASH_COMPLETE;
+
+    /* Write emulated eeprom contents from memory to compacted flash */
+    uint16_t *src  = (uint16_t *)DataBuf;
+    uintptr_t dest = FEE_PAGE_BASE_ADDRESS;
+    uint16_t  value;
+    for (; dest < FEE_PAGE_LAST_ADDRESS; ++src, dest += 2) {
+        value = *src;
+        if (value) {
+            eeprom_printf("FLASH_ProgramHalfWord(0x%04x, 0x%04x)\n", (uint32_t)dest, ~value);
+            FLASH_Status status = FLASH_ProgramHalfWord(dest, ~value);
+            if (status != FLASH_COMPLETE) final_status = status;
+        }
     }
 
-    // calculate which page is affected (Pagenum1/Pagenum2...PagenumN)
-    page = FEE_ADDR_OFFSET(Address) / FEE_PAGE_SIZE;
+    FLASH_Lock();
 
-    // if current data is 0xFF, the byte is empty, just overwrite with the new one
-    if ((*(__IO uint16_t *)(FEE_PAGE_BASE_ADDRESS + FEE_ADDR_OFFSET(Address))) == FEE_EMPTY_WORD) {
-        FlashStatus = FLASH_ProgramHalfWord(FEE_PAGE_BASE_ADDRESS + FEE_ADDR_OFFSET(Address), (uint16_t)(0x00FF & DataByte));
+    if (debug_eeprom) {
+        println("eeprom_compacted:");
+        print_eeprom();
+    }
+
+    return final_status;
+}
+
+static uint8_t eeprom_write_direct_entry(uint16_t Address) {
+    /* Check if we can just write this directly to the compacted flash area */
+    uintptr_t directAddress = FEE_PAGE_BASE_ADDRESS + (Address & 0xFFFE);
+    if (*(uint16_t *)directAddress == FEE_EMPTY_WORD) {
+        /* Write the value directly to the compacted area without a log entry */
+        uint16_t value = ~*(uint16_t *)(&DataBuf[Address & 0xFFFE]);
+        /* Early exit if a write isn't needed */
+        if (value == FEE_EMPTY_WORD) return FLASH_COMPLETE;
+
+        FLASH_Unlock();
+
+        eeprom_printf("FLASH_ProgramHalfWord(0x%08x, 0x%04x) [DIRECT]\n", (uint32_t)directAddress, value);
+        FLASH_Status status = FLASH_ProgramHalfWord(directAddress, value);
+
+        FLASH_Lock();
+        return status;
+    }
+    return 0;
+}
+
+static uint8_t eeprom_write_log_word_entry(uint16_t Address) {
+    FLASH_Status final_status = FLASH_COMPLETE;
+
+    uint16_t value = *(uint16_t *)(&DataBuf[Address]);
+    eeprom_printf("eeprom_write_log_word_entry(0x%04x): 0x%04x\n", Address, value);
+
+    /* MSB signifies the lowest 128-byte optimization is not in effect */
+    uint16_t encoding = FEE_WORD_ENCODING;
+    uint8_t  entry_size;
+    if (value <= 1) {
+        encoding |= value << 13;
+        entry_size = 2;
     } else {
-        // Copy Page to a buffer
-        memcpy(DataBuf, (uint8_t *)FEE_PAGE_BASE_ADDRESS + (page * FEE_PAGE_SIZE), FEE_PAGE_SIZE);  // !!! Calculate base address for the desired page
+        encoding |= FEE_VALUE_NEXT;
+        entry_size = 4;
+        /* Writes to addresses less than 128 are byte log entries */
+        Address -= FEE_BYTE_RANGE;
+    }
+
+    /* if we can't find an empty spot, we must compact emulated eeprom */
+    if (empty_slot > (uint16_t *)(FEE_WRITE_LOG_LAST_ADDRESS - entry_size)) {
+        /* compact the write log into the compacted flash area */
+        return eeprom_compact();
+    }
+
+    /* Word log writes should be word-aligned.  Take back a bit */
+    Address >>= 1;
+    Address |= encoding;
+
+    /* ok we found a place let's write our data */
+    FLASH_Unlock();
+
+    /* address */
+    eeprom_printf("FLASH_ProgramHalfWord(0x%08x, 0x%04x)\n", (uint32_t)empty_slot, Address);
+    final_status = FLASH_ProgramHalfWord((uintptr_t)empty_slot++, Address);
+
+    /* value */
+    if (encoding == (FEE_WORD_ENCODING | FEE_VALUE_NEXT)) {
+        eeprom_printf("FLASH_ProgramHalfWord(0x%08x, 0x%04x)\n", (uint32_t)empty_slot, ~value);
+        FLASH_Status status = FLASH_ProgramHalfWord((uintptr_t)empty_slot++, ~value);
+        if (status != FLASH_COMPLETE) final_status = status;
+    }
+
+    FLASH_Lock();
 
-        // check if new data is differ to current data, return if not, proceed if yes
-        if (DataByte == *(__IO uint8_t *)(FEE_PAGE_BASE_ADDRESS + FEE_ADDR_OFFSET(Address))) {
-            return 0;
+    return final_status;
+}
+
+static uint8_t eeprom_write_log_byte_entry(uint16_t Address) {
+    eeprom_printf("eeprom_write_log_byte_entry(0x%04x): 0x%02x\n", Address, DataBuf[Address]);
+
+    /* if couldn't find an empty spot, we must compact emulated eeprom */
+    if (empty_slot >= (uint16_t *)FEE_WRITE_LOG_LAST_ADDRESS) {
+        /* compact the write log into the compacted flash area */
+        return eeprom_compact();
+    }
+
+    /* ok we found a place let's write our data */
+    FLASH_Unlock();
+
+    /* Pack address and value into the same word */
+    uint16_t value = (Address << 8) | DataBuf[Address];
+
+    /* write to flash */
+    eeprom_printf("FLASH_ProgramHalfWord(0x%08x, 0x%04x)\n", (uint32_t)empty_slot, value);
+    FLASH_Status status = FLASH_ProgramHalfWord((uintptr_t)empty_slot++, value);
+
+    FLASH_Lock();
+
+    return status;
+}
+
+uint8_t EEPROM_WriteDataByte(uint16_t Address, uint8_t DataByte) {
+    /* if the address is out-of-bounds, do nothing */
+    if (Address >= FEE_DENSITY_BYTES) {
+        eeprom_printf("EEPROM_WriteDataByte(0x%04x, 0x%02x) [BAD ADDRESS]\n", Address, DataByte);
+        return FLASH_BAD_ADDRESS;
+    }
+
+    /* if the value is the same, don't bother writing it */
+    if (DataBuf[Address] == DataByte) {
+        eeprom_printf("EEPROM_WriteDataByte(0x%04x, 0x%02x) [SKIP SAME]\n", Address, DataByte);
+        return 0;
+    }
+
+    /* keep DataBuf cache in sync */
+    DataBuf[Address] = DataByte;
+    eeprom_printf("EEPROM_WriteDataByte DataBuf[0x%04x] = 0x%02x\n", Address, DataBuf[Address]);
+
+    /* perform the write into flash memory */
+    /* First, attempt to write directly into the compacted flash area */
+    FLASH_Status status = eeprom_write_direct_entry(Address);
+    if (!status) {
+        /* Otherwise append to the write log */
+        if (Address < FEE_BYTE_RANGE) {
+            status = eeprom_write_log_byte_entry(Address);
+        } else {
+            status = eeprom_write_log_word_entry(Address & 0xFFFE);
         }
+    }
+    if (status != 0 && status != FLASH_COMPLETE) {
+        eeprom_printf("EEPROM_WriteDataByte [STATUS == %d]\n", status);
+    }
+    return status;
+}
 
-        // manipulate desired data byte in temp data array if new byte is differ to the current
-        DataBuf[FEE_ADDR_OFFSET(Address) % FEE_PAGE_SIZE] = DataByte;
+uint8_t EEPROM_WriteDataWord(uint16_t Address, uint16_t DataWord) {
+    /* if the address is out-of-bounds, do nothing */
+    if (Address >= FEE_DENSITY_BYTES) {
+        eeprom_printf("EEPROM_WriteDataWord(0x%04x, 0x%04x) [BAD ADDRESS]\n", Address, DataWord);
+        return FLASH_BAD_ADDRESS;
+    }
 
-        // Erase Page
-        FlashStatus = FLASH_ErasePage(FEE_PAGE_BASE_ADDRESS + (page * FEE_PAGE_SIZE));
+    /* Check for word alignment */
+    FLASH_Status final_status = FLASH_COMPLETE;
+    if (Address % 2) {
+        final_status        = EEPROM_WriteDataByte(Address, DataWord);
+        FLASH_Status status = EEPROM_WriteDataByte(Address + 1, DataWord >> 8);
+        if (status != FLASH_COMPLETE) final_status = status;
+        if (final_status != 0 && final_status != FLASH_COMPLETE) {
+            eeprom_printf("EEPROM_WriteDataWord [STATUS == %d]\n", final_status);
+        }
+        return final_status;
+    }
+
+    /* if the value is the same, don't bother writing it */
+    uint16_t oldValue = *(uint16_t *)(&DataBuf[Address]);
+    if (oldValue == DataWord) {
+        eeprom_printf("EEPROM_WriteDataWord(0x%04x, 0x%04x) [SKIP SAME]\n", Address, DataWord);
+        return 0;
+    }
+
+    /* keep DataBuf cache in sync */
+    *(uint16_t *)(&DataBuf[Address]) = DataWord;
+    eeprom_printf("EEPROM_WriteDataWord DataBuf[0x%04x] = 0x%04x\n", Address, *(uint16_t *)(&DataBuf[Address]));
 
-        // Write new data (whole page) to flash if data has been changed
-        for (i = 0; i < (FEE_PAGE_SIZE / 2); i++) {
-            if ((__IO uint16_t)(0xFF00 | DataBuf[FEE_ADDR_OFFSET(i)]) != 0xFFFF) {
-                FlashStatus = FLASH_ProgramHalfWord((FEE_PAGE_BASE_ADDRESS + (page * FEE_PAGE_SIZE)) + (i * 2), (uint16_t)(0xFF00 | DataBuf[FEE_ADDR_OFFSET(i)]));
+    /* perform the write into flash memory */
+    /* First, attempt to write directly into the compacted flash area */
+    final_status = eeprom_write_direct_entry(Address);
+    if (!final_status) {
+        /* Otherwise append to the write log */
+        /* Check if we need to fall back to byte write */
+        if (Address < FEE_BYTE_RANGE) {
+            final_status = FLASH_COMPLETE;
+            /* Only write a byte if it has changed */
+            if ((uint8_t)oldValue != (uint8_t)DataWord) {
+                final_status = eeprom_write_log_byte_entry(Address);
             }
+            FLASH_Status status = FLASH_COMPLETE;
+            /* Only write a byte if it has changed */
+            if ((oldValue >> 8) != (DataWord >> 8)) {
+                status = eeprom_write_log_byte_entry(Address + 1);
+            }
+            if (status != FLASH_COMPLETE) final_status = status;
+        } else {
+            final_status = eeprom_write_log_word_entry(Address);
         }
     }
-    return FlashStatus;
+    if (final_status != 0 && final_status != FLASH_COMPLETE) {
+        eeprom_printf("EEPROM_WriteDataWord [STATUS == %d]\n", final_status);
+    }
+    return final_status;
 }
-/*****************************************************************************
- *  Read once data byte from a specified address.
- *******************************************************************************/
+
 uint8_t EEPROM_ReadDataByte(uint16_t Address) {
     uint8_t DataByte = 0xFF;
 
-    // Get Byte from specified address
-    DataByte = (*(__IO uint8_t *)(FEE_PAGE_BASE_ADDRESS + FEE_ADDR_OFFSET(Address)));
+    if (Address < FEE_DENSITY_BYTES) {
+        DataByte = DataBuf[Address];
+    }
+
+    eeprom_printf("EEPROM_ReadDataByte(0x%04x): 0x%02x\n", Address, DataByte);
 
     return DataByte;
 }
 
+uint16_t EEPROM_ReadDataWord(uint16_t Address) {
+    uint16_t DataWord = 0xFFFF;
+
+    if (Address < FEE_DENSITY_BYTES - 1) {
+        /* Check word alignment */
+        if (Address % 2) {
+            DataWord = DataBuf[Address] | (DataBuf[Address + 1] << 8);
+        } else {
+            DataWord = *(uint16_t *)(&DataBuf[Address]);
+        }
+    }
+
+    eeprom_printf("EEPROM_ReadDataWord(0x%04x): 0x%04x\n", Address, DataWord);
+
+    return DataWord;
+}
+
 /*****************************************************************************
  *  Wrap library in AVR style functions.
  *******************************************************************************/
-uint8_t eeprom_read_byte(const uint8_t *Address) {
-    const uint16_t p = (const uint32_t)Address;
-    return EEPROM_ReadDataByte(p);
-}
+uint8_t eeprom_read_byte(const uint8_t *Address) { return EEPROM_ReadDataByte((const uintptr_t)Address); }
 
-void eeprom_write_byte(uint8_t *Address, uint8_t Value) {
-    uint16_t p = (uint32_t)Address;
-    EEPROM_WriteDataByte(p, Value);
-}
+void eeprom_write_byte(uint8_t *Address, uint8_t Value) { EEPROM_WriteDataByte((uintptr_t)Address, Value); }
 
-void eeprom_update_byte(uint8_t *Address, uint8_t Value) {
-    uint16_t p = (uint32_t)Address;
-    EEPROM_WriteDataByte(p, Value);
-}
+void eeprom_update_byte(uint8_t *Address, uint8_t Value) { EEPROM_WriteDataByte((uintptr_t)Address, Value); }
 
-uint16_t eeprom_read_word(const uint16_t *Address) {
-    const uint16_t p = (const uint32_t)Address;
-    return EEPROM_ReadDataByte(p) | (EEPROM_ReadDataByte(p + 1) << 8);
-}
+uint16_t eeprom_read_word(const uint16_t *Address) { return EEPROM_ReadDataWord((const uintptr_t)Address); }
 
-void eeprom_write_word(uint16_t *Address, uint16_t Value) {
-    uint16_t p = (uint32_t)Address;
-    EEPROM_WriteDataByte(p, (uint8_t)Value);
-    EEPROM_WriteDataByte(p + 1, (uint8_t)(Value >> 8));
-}
+void eeprom_write_word(uint16_t *Address, uint16_t Value) { EEPROM_WriteDataWord((uintptr_t)Address, Value); }
 
-void eeprom_update_word(uint16_t *Address, uint16_t Value) {
-    uint16_t p = (uint32_t)Address;
-    EEPROM_WriteDataByte(p, (uint8_t)Value);
-    EEPROM_WriteDataByte(p + 1, (uint8_t)(Value >> 8));
-}
+void eeprom_update_word(uint16_t *Address, uint16_t Value) { EEPROM_WriteDataWord((uintptr_t)Address, Value); }
 
 uint32_t eeprom_read_dword(const uint32_t *Address) {
-    const uint16_t p = (const uint32_t)Address;
-    return EEPROM_ReadDataByte(p) | (EEPROM_ReadDataByte(p + 1) << 8) | (EEPROM_ReadDataByte(p + 2) << 16) | (EEPROM_ReadDataByte(p + 3) << 24);
+    const uint16_t p = (const uintptr_t)Address;
+    /* Check word alignment */
+    if (p % 2) {
+        /* Not aligned */
+        return (uint32_t)EEPROM_ReadDataByte(p) | (uint32_t)(EEPROM_ReadDataWord(p + 1) << 8) | (uint32_t)(EEPROM_ReadDataByte(p + 3) << 24);
+    } else {
+        /* Aligned */
+        return EEPROM_ReadDataWord(p) | (EEPROM_ReadDataWord(p + 2) << 16);
+    }
 }
 
 void eeprom_write_dword(uint32_t *Address, uint32_t Value) {
-    uint16_t p = (const uint32_t)Address;
-    EEPROM_WriteDataByte(p, (uint8_t)Value);
-    EEPROM_WriteDataByte(p + 1, (uint8_t)(Value >> 8));
-    EEPROM_WriteDataByte(p + 2, (uint8_t)(Value >> 16));
-    EEPROM_WriteDataByte(p + 3, (uint8_t)(Value >> 24));
-}
-
-void eeprom_update_dword(uint32_t *Address, uint32_t Value) {
-    uint16_t p             = (const uint32_t)Address;
-    uint32_t existingValue = EEPROM_ReadDataByte(p) | (EEPROM_ReadDataByte(p + 1) << 8) | (EEPROM_ReadDataByte(p + 2) << 16) | (EEPROM_ReadDataByte(p + 3) << 24);
-    if (Value != existingValue) {
+    uint16_t p = (const uintptr_t)Address;
+    /* Check word alignment */
+    if (p % 2) {
+        /* Not aligned */
         EEPROM_WriteDataByte(p, (uint8_t)Value);
-        EEPROM_WriteDataByte(p + 1, (uint8_t)(Value >> 8));
-        EEPROM_WriteDataByte(p + 2, (uint8_t)(Value >> 16));
+        EEPROM_WriteDataWord(p + 1, (uint16_t)(Value >> 8));
         EEPROM_WriteDataByte(p + 3, (uint8_t)(Value >> 24));
+    } else {
+        /* Aligned */
+        EEPROM_WriteDataWord(p, (uint16_t)Value);
+        EEPROM_WriteDataWord(p + 2, (uint16_t)(Value >> 16));
     }
 }
 
+void eeprom_update_dword(uint32_t *Address, uint32_t Value) { eeprom_write_dword(Address, Value); }
+
 void eeprom_read_bl