Detailed explanation of reading and writing flash in STM32

1: To program the STM32 internal FLASH, you need to follow the following process:

　　1. Flash unlock

　　2. Clear related flags

　　3. Erase FLASH (the reason for erasing first and then writing is for the convenience of industrial production, that is, the convenience of physical implementation)

　　4. Write to FLASH

　　5. Lock FLASH

(1) Get status: FLASH_Status FLASH_GetStatus(void);

The return value is defined by the enumeration type.

 typedef enum

{ 

   FLASH_BUSY = 1,  //忙

   FLASH_ERROR_PG, //Programming error

   FLASH_ERROR_WRP, //Write protection error

   FLASH_COMPLETE, // Operation completed

   FLASH_TIMEOUT // Operation timeout

 }FLASH_Status;

(2) FLASH_Unlock(); //Unlock function (must be unlocked before writing to the flash)

(3) FLASH_ClearFlag(); // Clear all existing flags

(4) There are three erase functions:

FLASH_Status FLASH_ErasePage(uint32_t Page_Address);

FLASH_Status FLASH_EraseAllPages(void);

FLASH_Status FLASH_EraseOptionBytes(void);

(5) Write function:

FLASHStatus FLASH_ProgramWord(uint32_t Address, uint32_t Data); //32-bit word write function

FLASHStatus FLASH_ProgramHalfWord(uint32_t Address,uint32_t Data); //16-bit half-word write

FLASHStatus FLASH_ProgramOptionByteData(uint32_t Address,uint32_t Data); //User byte write

int write_flash(u32 StartAddr,u16 *buf,u16 len)

{

    volatile FLASH_Status FLASHStatus;

u32 FlashAddr;

len=(len+1)/2;

FLASH_Unlock(); //1. Unlock function (must be unlocked before writing to the flash)

    FLASH_ClearFlag(FLASH_FLAG_BSY | FLASH_FLAG_EOP | FLASH_FLAG_PGERR | FLASH_FLAG_WRPERR); //2. Clear all existing flags

FlashAddr=StartAddr;

FLASH_ErasePage(StartAddr); //3. Erase a flash page

    while(len--)

    {

      //FLASH_ProgramHalfWord is a write function, the return value is the status of the flash (5 types)

      FLASHStatus = FLASH_ProgramHalfWord(FlashAddr,*buf++);

      if (FLASHStatus != FLASH_COMPLETE) //FLASH_COMPLETE indicates flash completion

      {

        //printf("FLSH :Error %08X\n\r",FLASHStatus);

        return -1;

      }

      FlashAddr += 2;

    }

FLASH_Lock();

return 0;

}

2. FLASH reading method

    *(uint32_t *)0x8000000; //read a word

　　*(uint8_t *)0x8000000; //read a byte;

　　*(uint16_t *)0x8000000; //read half word;  

　　Example:

　　uint8_t data;

　　data = *(uint8_t *)0x8000000; // read the data at address 0x8000000 in FLASH

int read_flash(u32 StartAddr,u32 *buf,u16 len) //Read one word 4 bytes at a time

{

len=(len+3)/4;

while(len--)

        {

*buf=*(__IO uint32_t *)StartAddr;

                 StartAddr=StartAddr+4;

                 buf++;

}

        return 0;

}

Three: Several useful sub-functions

/*

Function: Write data to the specified address

Parameter description: addr: address of the FLASH page to be written

          p: the address of the variable to be written (the array must be of type uint8_t and the number of elements must be an even number)

          Byte_Num: The number of bytes written to the variable (must be an even number)

*/

　　void FLASH_WriteByte(uint32_t addr , uint8_t *p , uint16_t Byte_Num)

　　{

　　        uint32_t HalfWord;

　　        Byte_Num = Byte_Num/2;

　　        FLASH_Unlock();

　　        FLASH_ClearFlag(FLASH_FLAG_BSY | FLASH_FLAG_EOP | FLASH_FLAG_PGERR | FLASH_FLAG_WRPRTERR);

　　        FLASH_ErasePage(addr);

　　        while(Byte_Num --)

　　        {

　　                HalfWord=*(p++);

　　                HalfWord|=*(p++)<<8;

　　                FLASH_ProgramHalfWord(addr, HalfWord);

　　                addr += 2;

　　        }

　　        FLASH_Lock();

　　}

　　example:

　　uint8_t data[100];

　　FLASH_WriteByte(0x8000000, data, 100);/*The data in the array data is written into FLASH*/

/*

Function: Read data from the specified address

Parameter description: addr address read from FLASH

          p is the address of the variable to be stored after reading (the array must be of type uint8_t)

          Byte_Num The number of bytes to be read

*/

　　void FLASH_ReadByte(uint32_t addr , uint8_t *p , uint16_t Byte_Num)

　　{

　　  while(Byte_Num--)

　　  {

　　   *(p++)=*((uint8_t*)addr++);

　　  }

　　}

　　example:

　　uint8_t data[101];

　　FLASH_ReadByte(0x8000001, data, 101);/*The data in FLASH is read into the array data*/

hardware_conf.h中：

//64 flash

#define ADDRESS_START_ADDR ((u32)0x0800EC00) //59: store domain name and port number

#define TIME_START_ADDR ((u32)0x0800F000) //60: storage time

#define KEYS_START_ADDR ((u32)0x0800F400) //61: store various keys

#define MACHINEID_START_ADDR ((u32)0x0800F800) //62: store machine code

#define VERSION_START_ADDR ((u32)0x0800FC00) //63: store version number

In main():

//Get the flash content

void getFlash()

{

      /*Read machine code*/

    u8 machineId[19]="";

    read_flash(MACHINEID_START_ADDR, (u32 *) machineId, 19);

    strncpy(MachineID_Default, machineId, 18);

    /*Read time*/   

    u8 times[20]="";

    read_flash(TIME_START_ADDR, (u32 *) times, 20);

    char timeKey[2]="";

    strncpy(timeKey, times, 1);

    /*Read keys*/

    u8 out_data[220];

    read_flash(KEYS_START_ADDR, (u32 *) out_data, 220);

  }

//Write various keys to flash

int getAllMessage() 

{

    char in_data[220];

    //The following are the variables that falsh needs to store

    sprintf(in_data, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s",isFisrt,community_code,address,swipe,code_overtime,myKey1,Private_Key,check_pw);

    if(strlen(in_data)==96&&in_data[0]=='N' &&in_data[1]=='\n'&&in_data[63]=='\n'&&in_data[65]=='\n'&&in_data[69]=='\n'&&in_data[75]=='\n'&&in_data[82]=='\n'&&in_data[89]=='\n')

    {

      write_flash(KEYS_START_ADDR, (u16 *) in_data, 220);

      ACCLOG("write keys success\n");

      return 1;

    }else{

      ACCLOG("write keys fail...\n");

      return 0;

    }

}