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cleanup

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combine preamble searches (thanks @iceman1001)
simplify Em410xDecode
fix bug in removeParity (I made recently)
move Unique TAG ID printout to avoid confusion
This commit is contained in:
marshmellow42 2017-02-23 13:53:40 -05:00
commit e88096ba25
4 changed files with 41 additions and 58 deletions
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87
common/lfdemod.c
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@ -78,7 +78,7 @@ size_t removeParity(uint8_t *BitStream, size_t startIdx, uint8_t pLen, uint8_t p
parityWd = (parityWd << 1) | BitStream[startIdx+word+bit];
BitStream[j++] = (BitStream[startIdx+word+bit]);
}
if (word+pLen >= bLen) break;
if (word+pLen > bLen) break;
j--; // overwrite parity with next data
// if parity fails then return 0
@ -150,38 +150,28 @@ uint32_t bytebits_to_byteLSBF(uint8_t *src, size_t numbits)
//search for given preamble in given BitStream and return success=1 or fail=0 and startIndex and length
uint8_t preambleSearch(uint8_t *BitStream, uint8_t *preamble, size_t pLen, size_t *size, size_t *startIdx)
{
// Sanity check. If preamble length is bigger than bitstream length.
if ( *size <= pLen ) return 0;
uint8_t foundCnt=0;
for (int idx=0; idx < *size - pLen; idx++){
if (memcmp(BitStream+idx, preamble, pLen) == 0){
//first index found
foundCnt++;
if (foundCnt == 1){
*startIdx = idx;
}
if (foundCnt == 2){
*size = idx - *startIdx;
return 1;
}
}
}
return 0;
return (preambleSearchEx(BitStream, preamble, pLen, size, startIdx, false)) ? 1 : 0;
}
// search for given preamble in given BitStream and return success=1 or fail=0 and startIndex (where it was found)
// does not look for a repeating preamble
// em4x05/4x69 only sends preamble once, so look for it once in the first pLen bits
// leave it generic so it could be reused later...
bool onePreambleSearch(uint8_t *BitStream, uint8_t *preamble, size_t pLen, size_t size, size_t *startIdx) {
// search for given preamble in given BitStream and return success=1 or fail=0 and startIndex (where it was found) and length if not fineone
// fineone does not look for a repeating preamble for em4x05/4x69 sends preamble once, so look for it once in the first pLen bits
bool preambleSearchEx(uint8_t *BitStream, uint8_t *preamble, size_t pLen, size_t *size, size_t *startIdx, bool findone) {
// Sanity check. If preamble length is bigger than bitstream length.
if ( size <= pLen ) return false;
for (size_t idx = 0; idx < size - pLen; idx++) {
if ( *size <= pLen ) return false;
uint8_t foundCnt = 0;
for (size_t idx = 0; idx < *size - pLen; idx++) {
if (memcmp(BitStream+idx, preamble, pLen) == 0) {
if (g_debugMode) prnt("DEBUG: preamble found at %u", idx);
*startIdx = idx;
return true;
//first index found
foundCnt++;
if (foundCnt == 1) {
if (g_debugMode) prnt("DEBUG: preamble found at %u", idx);
*startIdx = idx;
if (findone) return true;
} else if (foundCnt == 2) {
*size = idx - *startIdx;
return true;
}
}
}
return false;
@ -217,39 +207,32 @@ size_t findModStart(uint8_t dest[], size_t size, uint8_t threshold_value, uint8_
//takes 1s and 0s and searches for EM410x format - output EM ID
uint8_t Em410xDecode(uint8_t *BitStream, size_t *size, size_t *startIdx, uint32_t *hi, uint64_t *lo)
{
//no arguments needed - built this way in case we want this to be a direct call from "data " cmds in the future
// otherwise could be a void with no arguments
//set defaults
uint32_t i = 0;
//sanity checks
if (*size < 64) return 0;
if (BitStream[1]>1) return 0; //allow only 1s and 0s
// 111111111 bit pattern represent start of frame
// include 0 in front to help get start pos
uint8_t preamble[] = {0,1,1,1,1,1,1,1,1,1};
uint32_t idx = 0;
uint32_t parityBits = 0;
uint8_t errChk = 0;
uint8_t FmtLen = 10;
uint8_t FmtLen = 10; // sets of 4 bits = end data
*startIdx = 0;
errChk = preambleSearch(BitStream, preamble, sizeof(preamble), size, startIdx);
if (errChk == 0 || *size < 64) return 0;
if (*size > 64) FmtLen = 22;
*startIdx += 1; //get rid of 0 from preamble
idx = *startIdx + 9;
for (i=0; i<FmtLen; i++){ //loop through 10 or 22 sets of 5 bits (50-10p = 40 bits or 88 bits)
parityBits = bytebits_to_byte(BitStream+(i*5)+idx,5);
//check even parity - quit if failed
if (parityTest(parityBits, 5, 0) == 0) return 0;
//set uint64 with ID from BitStream
for (uint8_t ii=0; ii<4; ii++){
*hi = (*hi << 1) | (*lo >> 63);
*lo = (*lo << 1) | (BitStream[(i*5)+ii+idx]);
}
if (*size == 110) FmtLen = 22; // 22 sets of 4 bits
//skip last 4bit parity row for simplicity
*size = removeParity(BitStream, *startIdx + sizeof(preamble), 5, 0, FmtLen * 5);
if (*size == 40) { // std em410x format
*hi = 0;
*lo = ((uint64_t)(bytebits_to_byte(BitStream, 8)) << 32) | (bytebits_to_byte(BitStream + 8, 32));
} else if (*size == 88) { // long em format
*hi = (bytebits_to_byte(BitStream, 24));
*lo = ((uint64_t)(bytebits_to_byte(BitStream + 24, 32)) << 32) | (bytebits_to_byte(BitStream + 24 + 32, 32));
} else {
return 0;
}
if (errChk != 0) return 1;
//skip last 5 bit parity test for simplicity.
// *size = 64 | 128;
return 0;
return 1;
}
//by marshmellow