[英]Read a double from 32-bit address flash memory
我有一個32位微控制器,並且剛剛向閃存中寫入了兩倍。 現在,我想從內存中讀取double,但是當微控制器進入硬故障處理程序時,我在做非法的事情。
首先,我嘗試了:
double Flash_Read64(uint32_t address)
{
return *((double *) address);
}
但這沒有用。 是因為地址是32位並且(double *)期望是64位嗎?
然后,我嘗試:
double Flash_Read64(uint32_t address)
{
uint64_t temp;
double * tempPtr = (double *) &temp;
//Increment address.
address += 4;
//Get MSB.
temp = (*((uint32_t *) (address)));
//Shift MSB to upper half.
temp = (temp << 32);
//Decrement address.
address -= 4;
//Get LSB.
temp |= (*((uint32_t *) address));
return *tempPtr;
}
但仍然無法正常工作。
有什么建議么?
編輯:
bool_t Flash_Write64Address(uint32_t address, double data)
{
uint32_t MSB, LSB;
uint32_t * tempPtr = (uint32_t *) &data;
//Get LSB.
LSB = tempPtr[0];
//Write LSB to flash.
flashStatus = FLASH_ProgramWord(address, LSB);
if(flashStatus != FLASH_COMPLETE)
{
DEBUG("Failed to write to flash at address: %u", (unsigned int) address);
return FALSE;
}
//Increment address.
address += 4;
//Get MSB.
MSB = tempPtr[1];
//Write MSB to flash.
flashStatus = FLASH_ProgramWord(address, MSB);
if(flashStatus != FLASH_COMPLETE)
{
DEBUG("Failed to write to flash at address: %u", (unsigned int) address);
return FALSE;
}
return TRUE;
}
為了簡化和避免對齊問題(我認為正是對齊問題引起了悲傷。)
typedef union {
double d;
uint32_t u[2];
} Xlate;
bool_t Flash_Write64Address(uint32_t address, double data) {
Xlate x;
x.d = data;
for (int i=0; i < 2; i++) {
int flashStatus = FLASH_ProgramWord(address, x.u[i]);
address += 4;
if(flashStatus != FLASH_COMPLETE) {
return FALSE;
}
return TRUE;
}
double Flash_Read64(uint32_t address) {
Xlate x;
x.u[0] = *((uint32_t *) address);
x.u[1] = *((uint32_t *) (address + 4));
return x.d;
}
[編輯]
我假設該address
表示一個四字節對齊的地址(至少2位為0)。 如果address
沒有8-byte alignment
(至少3位為0),並且需要double
訪問,則
return *((double *) address);
// or
return *tempPtr;
會導致總線故障。 如果是這樣,則上面的代碼應處理此問題。
或者,代碼可以確保address
具有8-byte alignment
。
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