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mmc_crc7.cpp
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mmc_crc7.cpp
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//
// MMC Card CRC7 calculator and checker
// www.openchip.org
//
//
#include <iostream>
#include <stdio.h>
using namespace std;
char crc7[8];
char cmd[49];
void do_crc7(char c) {
char c3;
char c0;
// last stage and input bit
c0 = (crc7[6] == c) ? '0' : '1';
//
c3 = (crc7[2] == c0) ? '0' : '1';
// shift register
crc7[6] = crc7[5];
crc7[5] = crc7[4];
crc7[4] = crc7[3];
crc7[3] = c3;
crc7[2] = crc7[1];
crc7[1] = crc7[0];
crc7[0] = c0;
}
/*
CMD17 Argument=0x00000100 CRC7=0x43 OK, checked!
CMD17 Argument=0x00004000 CRC7=0x8F OK, checked!
*/
void calc_crc(int command, unsigned int arg) {
int i;
unsigned int mask;
// fill CMD
mask = 1;
for (i=0;i<6;i++) {
if (mask & command) {
cmd[7-i] = '1';
} else {
cmd[7-i]='0';
}
mask <<= 1;
}
// fill ARG
mask = 1;
for (i=0;i<32;i++) {
if (mask & arg) {
cmd[39-i] = '1';
} else {
cmd[39-i]='0';
}
mask <<= 1;
}
// clear CRC
for (i=0;i<7;i++) crc7[i] = '0';
// calc CRC
for (i=0;i<40;i++) do_crc7(cmd[i]);
// copy CRC
cmd[40] = crc7[6];
cmd[41] = crc7[5];
cmd[42] = crc7[4];
cmd[43] = crc7[3];
cmd[44] = crc7[2];
cmd[45] = crc7[1];
cmd[46] = crc7[0];
}
int main (int argc, char *argv[])
{
char quit;
int i;
// clear CRC
crc7[7] = 0;
for (i=0;i<7;i++) crc7[i] = '0';
// clear CMD, ARG
cmd[48] = 0;
for (i=0;i<48;i++) cmd[i] = '0';
cmd[1] = '1'; // Start bit
cmd[47] = '1'; // Stop Bit
// check CRC calculation
calc_crc(0,0); printf("\n\rTest CMD0 ,0x0 %s", cmd);
calc_crc(17,0x100); printf("\n\rTest CMD17,0x0100 %s", cmd);
calc_crc(17,0x4000); printf("\n\rTest CMD17,0x04000 %s", cmd);
printf("\n\rCalc CRCs");
calc_crc(0,0); printf("\n\rTest CMD0 ,0x0 %s", cmd);
calc_crc(1,0x80FF8000); printf("\n\rTest CMD1 ,0x80FF8000 %s", cmd);
calc_crc(2,0); printf("\n\rTest CMD2 ,0x0 %s", cmd);
calc_crc(3,0x10000); printf("\n\rTest CMD3 ,0x10000 %s", cmd);
calc_crc(7,0x10000); printf("\n\rTest CMD7 ,0x10000 %s", cmd);
calc_crc(11,0x0000); printf("\n\rTest CMD11,0x00000 %s", cmd);
calc_crc(55,0x0000); printf("\n\rTest CMD55,0x00000 %s", cmd);
calc_crc(41,0x80FF8000); printf("\n\rTest ACMD41,0x80FF8000 %s", cmd);
cin >>quit;
return 0;
}