Flash更适合作为程序存储器，EEPROM更适合作为数据存储器，存储大量数据的时候就需要使用EEPROM，廉价的MCU往往只有FLASH而没有EEPROM，所以这个时候就需要外加EEPROM或者选择一些别的办法，使用Flash模拟EEPROM就是一个很好的选择，说白了就是使用stm32内部flash里面一部分空间用来保存数据，不只是保存程序代码。
Flash是按照扇区操作，EEPROM是按字节操作
offaddr=WriteAddr-STM32_FLASH_BASE; //实际偏移地址.
secpos=offaddr/STM_SECTOR_SIZE; //扇区地址，将偏移地址除以每个扇区的大小
secoff=(offaddr%STM_SECTOR_SIZE)/2; //在扇区内的偏移（2字节）
secremain=STM_SECTOR_SIZE/2-secoff; //扇区剩余空间大小
S
T
M
32
_
F
L
A
S
H
_
B
A
S
E
=
0
X
8000000
STM32\_FLASH\_BASE = 0X800 0000
STM32_FLASH_BASE=0X8000000
假设写入地址为
W
r
i
t
e
A
d
d
r
=
0
X
8030000
WriteAddr=0X8030000
WriteAddr=0X8030000
那么偏移地址就是
s
e
c
p
o
s
=
0
X
8030000
−
0
X
8000000
=
0
X
0030000
secpos=0X8030000-0X8000000=0X0030000
secpos=0X8030000−0X8000000=0X0030000
void STMFLASH_Write(u32 WriteAddr,u16 *pBuffer,u16 NumToWrite)
{
u32 secpos; //扇区地址
u16 secoff; //扇区内偏移地址(16位字计算)
u16 secremain; //扇区内剩余地址(16位字计算)
u16 i;
u32 offaddr; //去掉0X08000000后的地址（也就是相对于基地址的偏移量）
if(WriteAddr<STM32_FLASH_BASE|| //小于基地址
(WriteAddr>=(STM32_FLASH_BASE+1024*STM32_FLASH_SIZE)))//超出了最大地址
{
return;
}//非法地址
FLASH_Unlock(); //解锁
offaddr=WriteAddr-STM32_FLASH_BASE; //实际偏移地址.
secpos=offaddr/STM_SECTOR_SIZE; //扇区地址，将偏移地址除以每个扇区的大小
secoff=(offaddr%STM_SECTOR_SIZE)/2; //在扇区内的偏移（2字节）
secremain=STM_SECTOR_SIZE/2-secoff; //扇区剩余空间大小
if(NumToWrite<=secremain){ // 如果剩余的扇区空间足够
secremain=NumToWrite; //？
}
while(1)
{
STMFLASH_Read(secpos*STM_SECTOR_SIZE+STM32_FLASH_BASE,
STMFLASH_BUF,STM_SECTOR_SIZE/2);//读出整个扇区的内容
for(i=0;i<secremain;i++)//校验数据
{
if(STMFLASH_BUF[secoff+i]!=0XFFFF)break;//需要擦除
}
if(i<secremain)//需要擦除
{
FLASH_ErasePage(secpos*STM_SECTOR_SIZE+STM32_FLASH_BASE);//擦除这个扇区
for(i=0;i<secremain;i++)//复制
{
STMFLASH_BUF[i+secoff]=pBuffer[i];
}
STMFLASH_Write_NoCheck(secpos*STM_SECTOR_SIZE+STM32_FLASH_BASE,STMFLASH_BUF,STM_SECTOR_SIZE/2);//写入整个扇区
}else STMFLASH_Write_NoCheck(WriteAddr,pBuffer,secremain);//写已经擦除了的,直接写入扇区剩余区间.
if(NumToWrite==secremain)break;//写入结束了
else//写入未结束
{
secpos++; //扇区地址增1
secoff=0; //偏移位置为0
pBuffer+=secremain; //指针偏移
WriteAddr+=secremain; //写地址偏移
NumToWrite-=secremain; //字节(16位)数递减
if(NumToWrite>(STM_SECTOR_SIZE/2))secremain=STM_SECTOR_SIZE/2;//下一个扇区还是写不完
else secremain=NumToWrite;//下一个扇区可以写完了
}
};
FLASH_Lock();//上锁
}
在开发板上有两个跳线帽，可以用来切换B0（Boot0）和B1（Boot1），模式如下
| B0 | B1 | 描述 |
|---|---|---|
| GND | GND | 从0x8000000运行（主存储器基地址） |
| 3.3 | GND | 从信息块运行 |
#ifndef __STMFLASH_H__
#define __STMFLASH_H__
#include "sys.h"
#define STM32_FLASH_SIZE 256 //定义flash大小
#define STM32_FLASH_WREN 1 //允许写
#define STM32_FLASH_BASE 0x08000000 //STM32 FLASH基地址
u16 STMFLASH_ReadHalfWord(u32 faddr); //读半字（2字节）
void STMFLASH_WriteLenByte(u32 WriteAddr,u32 DataToWrite,u16 Len); //ָ写指定长度字节
u32 STMFLASH_ReadLenByte(u32 ReadAddr,u16 Len); //ָ读给定长度字节
void STMFLASH_Write(u32 WriteAddr,u16 *pBuffer,u16 NumToWrite); //写
void STMFLASH_Read(u32 ReadAddr,u16 *pBuffer,u16 NumToRead); //读
//�����
void Test_Write(u32 WriteAddr,u16 WriteData);
#endif
#include "stmflash.h"
#include "delay.h"
u16 STMFLASH_ReadHalfWord(u32 faddr)//给地址读取半字
{
return *(vu16*)faddr;
}
#if STM32_FLASH_WREN
void STMFLASH_Write_NoCheck(u32 WriteAddr,u16 *pBuffer,u16 NumToWrite)//进行不检查的写
{
u16 i;
for(i=0;i<NumToWrite;i++)//写numtowrite个半字
{
FLASH_ProgramHalfWord(WriteAddr,pBuffer[i]);
WriteAddr+=2;//写地址+2（由于是半字）
}
}
#if STM32_FLASH_SIZE<256
#define STM_SECTOR_SIZE 1024 //�ֽ�
#else
#define STM_SECTOR_SIZE 2048
#endif
u16 STMFLASH_BUF[STM_SECTOR_SIZE/2];
void STMFLASH_Write(u32 WriteAddr,u16 *pBuffer,u16 NumToWrite)//写
{
u32 secpos;
u16 secoff;
u16 secremain;
u16 i;
u32 offaddr;
if(WriteAddr<STM32_FLASH_BASE||(WriteAddr>=(STM32_FLASH_BASE+1024*STM32_FLASH_SIZE)))return;//在可写空间之外写
FLASH_Unlock(); //解锁flash
offaddr=WriteAddr-STM32_FLASH_BASE;//计算偏移地址
secpos=offaddr/STM_SECTOR_SIZE; //计算所在sector的地址
secoff=(offaddr%STM_SECTOR_SIZE)/2; //计算sector的偏移量
secremain=STM_SECTOR_SIZE/2-secoff; //计算sector-sector偏移量
if(NumToWrite<=secremain)secremain=NumToWrite;
while(1)
{
STMFLASH_Read(secpos*STM_SECTOR_SIZE+STM32_FLASH_BASE,STMFLASH_BUF,STM_SECTOR_SIZE/2);
for(i=0;i<secremain;i++)
{
if(STMFLASH_BUF[secoff+i]!=0XFFFF)break;
}
if(i<secremain)
{
FLASH_ErasePage(secpos*STM_SECTOR_SIZE+STM32_FLASH_BASE);//擦除页
for(i=0;i<secremain;i++)
{
STMFLASH_BUF[i+secoff]=pBuffer[i]; //写
}
STMFLASH_Write_NoCheck(secpos*STM_SECTOR_SIZE+STM32_FLASH_BASE,STMFLASH_BUF,STM_SECTOR_SIZE/2);
}else STMFLASH_Write_NoCheck(WriteAddr,pBuffer,secremain);
if(NumToWrite==secremain)break;
else
{
secpos++;
secoff=0;
pBuffer+=secremain;
WriteAddr+=secremain;
NumToWrite-=secremain;
if(NumToWrite>(STM_SECTOR_SIZE/2))secremain=STM_SECTOR_SIZE/2;
else secremain=NumToWrite;
}
};
FLASH_Lock();
}
#endif
void STMFLASH_Read(u32 ReadAddr,u16 *pBuffer,u16 NumToRead)//将数据读到缓存数组里
{
u16 i;
for(i=0;i<NumToRead;i++)
{
pBuffer[i]=STMFLASH_ReadHalfWord(ReadAddr);
ReadAddr+=2;
}
}
void Test_Write(u32 WriteAddr,u16 WriteData)//测试写一个半字
{
STMFLASH_Write(WriteAddr,&WriteData,1);
}
#include "delay.h"
#include "sys.h"
#include "key.h"
#include "oled.h"
#include "stmflash.h"
const u8 TEXT_Buffer[]={"STM32 FLASH TEST"};
#define SIZE sizeof(TEXT_Buffer) //数组长度
#define FLASH_SAVE_ADDR 0X08020000 //设置FLASH 保存地址(必须为偶数，且其值要大于本代码所占用FLASH的大小+0X08000000)
int main(void)
{
u8 datatemp[SIZE];
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);// 设置中断优先级分组2
delay_init(); //延时函数初始化
KEY_Init(); //按键初始化
OLED_Init();
while(1)
{
if(KEY0)
{
OLED_Refresh();
//OLED_Refresh();
OLED_ShowString(0,0,"start write",16,1);
STMFLASH_Write(FLASH_SAVE_ADDR,(u16*)TEXT_Buffer,SIZE);
OLED_ShowString(0,16,"write finished",16,1);
OLED_ShowString(0,32," ",16,1);
OLED_Refresh();
}
if(!KEY0){
OLED_Refresh();
OLED_ShowString(0,0,"start read ",16,1);
STMFLASH_Read(FLASH_SAVE_ADDR,(u16*)datatemp,SIZE);
OLED_ShowString(0,16,"read data is ",16,1);
OLED_ShowString(0,32,datatemp,16,1);
OLED_Refresh();
}
}
}