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  1. /*
  2.  * nvram.c
  3.  *
  4.  *  Created on: 4 Jun 2017
  5.  *  Converted to use two 1K pages of STM32L1 Block Erasable Flash memory
  6.  *   instead of 4k of genuine word erasable NVRAM
  7.  *    on 1 Mar 2023
  8.  *      Author: Mike
  9.  */
  10.  
  11. /* Includes ------------------------------------------------------------------*/
  12. #include "stm32f1xx_hal.h"
  13.  
  14. #include "nvram.h"
  15.  
  16. // erase page size on STM32F103 is 1kbytes
  17. #define NVRAM_PAGESIZE (1024 / sizeof(nvram_info_t))
  18.  
  19. // decided to allocate 2 pages of Flash as NVRAM
  20. #define NVRAM_WORDS (2 * NVRAM_PAGESIZE)
  21.  
  22. // Flash hardware erases to all 0
  23. nvram_info_t const HARDWARE_ERASED = {.word = (uint32_t)0UL};
  24. // Marked as erased change to all 1
  25. nvram_info_t const MARKED_ERASED = {.word = (uint32_t)~0UL};
  26.  
  27. // allocate the memory for storing the NVRAM data
  28. nvram_info_t NVRAM_Base[NVRAM_WORDS] __attribute__((section(".nvram"))) = { [0 ... NVRAM_WORDS-1].word = (uint32_t)0UL}; // set by linker
  29.  
  30. static void
  31. WriteNVRAM(nvram_info_t *Address, nvram_info_t data)
  32. {
  33.   HAL_FLASH_Unlock();
  34.   HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD, (uint32_t)Address, data.word);
  35.   HAL_FLASH_Lock();
  36. }
  37.  
  38. static void
  39. EraseNVRAM(nvram_info_t *Address)
  40. {
  41.   FLASH_EraseInitTypeDef erase = {.TypeErase = FLASH_TYPEERASE_PAGES, .PageAddress = (uint32_t)Address, .NbPages = 1};
  42.   uint32_t err;
  43.   HAL_FLASH_Unlock();
  44.   HAL_FLASHEx_Erase(&erase, &err);
  45.   HAL_FLASH_Lock();
  46. }
  47.  
  48. // returns true if page crossed , used to trigger erasure of
  49. // the other page after copying out all data from other page to new page
  50.  
  51. static uint8_t _write_nvram_data(nvram_info_t data, int *pIndex)
  52. {
  53.   int base = *pIndex;
  54.   uint8_t pageCrossed = 0;
  55.  
  56.   // search for correct data
  57.   for (int ptr = 0; ptr < NVRAM_WORDS; ptr++)
  58.   {
  59.     int index = (ptr + base) % NVRAM_WORDS;
  60.     // erase the entry just found
  61.     if (NVRAM_Base[index].data.tag == data.data.tag)
  62.     {
  63.       // is this the same data as we are writing ? if so return immediately
  64.       if(NVRAM_Base[index].word == data.word)
  65.         return 0;
  66.       // different data
  67.       // erase previous data
  68.       WriteNVRAM(&NVRAM_Base[index], MARKED_ERASED);
  69.       base = index+1; // look at next element
  70.       break;
  71.     }
  72.   }
  73.   // search forward for next hardware erased element, use it
  74.   for (int offset = 0; offset < NVRAM_WORDS; offset++)
  75.   {
  76.     int index = (base + offset) % NVRAM_WORDS;
  77.  
  78.     if (NVRAM_Base[index].word == HARDWARE_ERASED.word)
  79.     {
  80.       // if we cross a page by incrementing into it need action
  81.       if (index % NVRAM_PAGESIZE == 0)
  82.         pageCrossed = 1;
  83.  
  84.       WriteNVRAM(&NVRAM_Base[index], data);
  85.       // now check to see if it actually wrote correctly
  86.       if (NVRAM_Base[index].word != data.word)
  87.       {
  88.         WriteNVRAM(&NVRAM_Base[index], MARKED_ERASED); // Set to all erased if the data did not write properly
  89.         continue;
  90.       }
  91.       // record where the data was written
  92.       *pIndex = index;
  93.       return pageCrossed;
  94.     }
  95.   }
  96.   // if it gets here, failure.
  97.   return 0;
  98. }
  99.  
  100. void write_nvram_data(nvram_info_t data)
  101. {
  102.   int index = 0;
  103.   // try the easy case - returns 0 , no further action
  104.   if (!_write_nvram_data(data, &index))
  105.     return;
  106.   // Returns 1, crossed page boundary with write of new data.
  107.   // Now have the index pointing into the page where we need to copy the data to
  108.   // for any data in the other page, copy it to the new page
  109.   int oldPageBase = index >= NVRAM_PAGESIZE ? 0 : NVRAM_PAGESIZE;
  110.   for (int i = oldPageBase; i < oldPageBase + NVRAM_WORDS; i++)
  111.   {
  112.     if (NVRAM_Base[i].word != HARDWARE_ERASED.word && NVRAM_Base[i].word != MARKED_ERASED.word)
  113.     {
  114.       int base = i;
  115.       // copy data forwards
  116.       _write_nvram_data(NVRAM_Base[i], &base);
  117.     }
  118.     // erase the page we just copied out of
  119.   }
  120.   EraseNVRAM(&NVRAM_Base[oldPageBase]);
  121. }
  122.  
  123. nvram_info_t *find_nvram_data(uint8_t searchTag)
  124. {
  125.   for (int ptr = 0; ptr < NVRAM_WORDS; ptr++)
  126.   {
  127.     if (NVRAM_Base[ptr].data.tag == searchTag)
  128.       return &NVRAM_Base[ptr];
  129.   }
  130.   return NULL;
  131. }
  132.