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Add support for Electra demodulation

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This commit is contained in:
Philippe Teuwen 2021-08-03 23:22:19 +02:00
commit ee22a824ce
7 changed files with 158 additions and 69 deletions
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91
common/lfdemod.c
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@ -253,6 +253,55 @@ size_t removeParity(uint8_t *bits, size_t startIdx, uint8_t pLen, uint8_t pType,
return bitCnt;
}
static size_t removeEm410xParity(uint8_t *bits, size_t startIdx, bool isLong, bool *validShort, bool *validShortExtended, bool *validLong) {
uint32_t parityWd = 0;
size_t bitCnt = 0;
bool validColParity = false;
bool validRowParity = true;
bool validRowParitySkipColP = true;
*validShort = false;
*validShortExtended = false;
*validLong = false;
uint8_t bLen = isLong ? 110 : 55;
uint16_t parityCol[4] = { 0, 0, 0, 0 };
for (int word = 0; word < bLen; word += 5) {
for (int bit = 0; bit < 5; bit++) {
if (word + bit >= bLen) break;
parityWd = (parityWd << 1) | bits[startIdx + word + bit];
if ((word <= 50) && (bit < 4))
parityCol[bit] = (parityCol[bit] << 1) | bits[startIdx + word + bit];
bits[bitCnt++] = (bits[startIdx + word + bit]);
}
if (word + 5 > bLen) break;
bitCnt--; // overwrite parity with next data
validRowParity &= parityTest(parityWd, 5, 0) != 0;
if (word == 50) { // column parity nibble on short EM and on Electra
validColParity = parityTest(parityCol[0], 11, 0) != 0;
validColParity &= parityTest(parityCol[1], 11, 0) != 0;
validColParity &= parityTest(parityCol[2], 11, 0) != 0;
validColParity &= parityTest(parityCol[3], 11, 0) != 0;
} else {
validRowParitySkipColP &= parityTest(parityWd, 5, 0) != 0;
}
parityWd = 0;
}
if (!isLong && validRowParitySkipColP && validColParity) {
*validShort = true;
}
if (isLong && validRowParity) {
*validLong = true;
}
if (isLong && validRowParitySkipColP && validColParity) {
*validShortExtended = true;
}
if (*validShort || *validShortExtended || *validLong) {
return bitCnt;
} else {
return 0;
}
}
// by marshmellow
// takes a array of binary values, length of bits per parity (includes parity bit),
// Parity Type (1 for odd; 0 for even; 2 Always 1's; 3 Always 0's), and binary Length (length to run)
@ -2122,7 +2171,6 @@ int Em410xDecode(uint8_t *bits, size_t *size, size_t *start_idx, uint32_t *hi, u
if (bits[1] > 1) return -1;
if (*size < 64) return -2;
uint8_t fmtlen;
*start_idx = 0;
// preamble 0111111111
@ -2131,32 +2179,29 @@ int Em410xDecode(uint8_t *bits, size_t *size, size_t *start_idx, uint32_t *hi, u
if (!preambleSearch(bits, preamble, sizeof(preamble), size, start_idx))
return -4;
// (iceman) if the preamble doesn't find two occuriences, this identification fails.
fmtlen = (*size == 128) ? 22 : 10;
bool validShort = false;
bool validShortExtended = false;
bool validLong = false;
*size = removeEm410xParity(bits, *start_idx + sizeof(preamble), *size == 128, &validShort, &validShortExtended, &validLong);
//skip last 4bit parity row for simplicity
*size = removeParity(bits, *start_idx + sizeof(preamble), 5, 0, fmtlen * 5);
switch (*size) {
case 40: {
// std em410x format
*hi = 0;
*lo = ((uint64_t)(bytebits_to_byte(bits, 8)) << 32) | (bytebits_to_byte(bits + 8, 32));
break;
}
case 88: {
// long em format
*hi = (bytebits_to_byte(bits, 24));
*lo = ((uint64_t)(bytebits_to_byte(bits + 24, 32)) << 32) | (bytebits_to_byte(bits + 24 + 32, 32));
break;
}
default:
return -6;
if (validShort) {
// std em410x format
*hi = 0;
*lo = ((uint64_t)(bytebits_to_byte(bits, 8)) << 32) | (bytebits_to_byte(bits + 8, 32));
// 1 = Short
return 1;
}
return 1;
if (validShortExtended || validLong) {
// store in long em format
*hi = (bytebits_to_byte(bits, 24));
*lo = ((uint64_t)(bytebits_to_byte(bits + 24, 32)) << 32) | (bytebits_to_byte(bits + 24 + 32, 32));
// 2 = Long
// 4 = ShortExtended
return ((int)validShortExtended << 2) + ((int)validLong << 1);
}
return -6;
}
// loop to get raw HID waveform then FSK demodulate the TAG ID from it
int HIDdemodFSK(uint8_t *dest, size_t *size, uint32_t *hi2, uint32_t *hi, uint32_t *lo, int *waveStartIdx) {
//make sure buffer has data