//by marshmellow
//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)
+int 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;
- if (BitStream[1]>1) return 0; //allow only 1s and 0s
+ if (BitStream[1]>1) return -1; //allow only 1s and 0s
// 111111111 bit pattern represent start of frame
// include 0 in front to help get start pos
uint8_t FmtLen = 10;
*startIdx = 0;
errChk = preambleSearch(BitStream, preamble, sizeof(preamble), size, startIdx);
- if (errChk == 0 || *size < 64) return 0;
+ if (errChk == 0 ) return -4;
+ if (*size < 64) return -3;
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;
+ if (parityTest(parityBits, 5, 0) == 0) return -5;
//set uint64 with ID from BitStream
for (uint8_t ii=0; ii<4; ii++){
*hi = (*hi << 1) | (*lo >> 63);