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//CopyRight:www.mcuisp.com
//版权: 单片机在线编程网
/**********************
reverse bits of DWORD
Input:
u32 data -- the input
Output:
u32 data -- the output
**********************/
u32 revbit(u32 data)
{
asm("rbit r0,r0");
return data;
};
/**********************
Calculate CRC32 of DWORD data array.
Input:
u32 *dworddata -- the array point
u32 dwordcount -- the data len in DWORD
Output:
u32 CRC32 -- the result
**********************/
u32 CalcCRC32(u32 *dworddata,u32 dwordcount)
{
u32 ui32;
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_CRC,ENABLE);
CRC->CR=1;
asm("NOP");asm("NOP");asm("NOP");//貌似CRC复位后需等会送数
for(;dwordcount>0;dwordcount--)
{
ui32=*dworddata;
dworddata++;
ui32=revbit(ui32);//输入位序颠倒一下
CRC->DR=ui32;
}
ui32=CRC->DR;
ui32=revbit(ui32);//输出位序颠倒一下
ui32^=0xffffffff;//异或
return ui32;
};
/**********************
test the CalcCRC32.
Input:
None
Output:
None
**********************/
void testCRC(void)
{
u32 ui32;
union{
u32 databuf32[256/4];
u8 databuf8[256];
};
databuf32[0]=0x41424344;//实际为44 43 42 41
ui32=CalcCRC32(databuf32+0,1);
Lcd_ClrRect(0,0,128,64);
DisplayBytes("CRC,Input:",0,0,65535,16,16);
DisplayAscii(toHex(databuf8[0]>>4),0,16);
DisplayAscii(toHex(databuf8[0]>>0),8,16);
DisplayAscii(toHex(databuf8[1]>>4),16,16);
DisplayAscii(toHex(databuf8[1]>>0),24,16);
DisplayAscii(toHex(databuf8[2]>>4),32,16);
DisplayAscii(toHex(databuf8[2]>>0),40,16);
DisplayAscii(toHex(databuf8[3]>>4),48,16);
DisplayAscii(toHex(databuf8[3]>>0),56,16);//44434241
DisplayBytes("CRC,Output:",0,32,65535,16,16);
DisplayAscii(toHex(ui32>>28),0,48);
DisplayAscii(toHex(ui32>>24),8,48);
DisplayAscii(toHex(ui32>>20),16,48);
DisplayAscii(toHex(ui32>>16),24,48);
DisplayAscii(toHex(ui32>>12),32,48);
DisplayAscii(toHex(ui32>>8),40,48);
DisplayAscii(toHex(ui32>>4),48,48);
DisplayAscii(toHex(ui32>>0),56,48);//847a7f6e
}
//可以看出，stm32f与主流计算工具有三点差别：
//1、输入位序颠倒,只需数据输入前颠倒位序
//2、输出位序颠倒，获得结果后再颠倒回来。
//3、异或0xffffffff
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Post By：2009-05-13 20:45:22
