Uart.parityLen = 0; // number of decoded parity bytes
Uart.shiftReg = 0; // shiftreg to hold decoded data bits
Uart.parityBits = 0; // holds 8 parity bits
- Uart.twoBits = 0x0000; // buffer for 2 Bits
- Uart.highCnt = 0;
+ Uart.fourBits = 0x00000000; // buffer for 4 Bits
Uart.startTime = 0;
Uart.endTime = 0;
}
static RAMFUNC bool MillerDecoding(uint8_t bit, uint32_t non_real_time)
{
- Uart.twoBits = (Uart.twoBits << 8) | bit;
+ Uart.fourBits = (Uart.fourBits << 8) | bit;
if (Uart.state == STATE_UNSYNCD) { // not yet synced
- if (Uart.highCnt < 2) { // wait for a stable unmodulated signal
- if (Uart.twoBits == 0xffff) {
- Uart.highCnt++;
- } else {
- Uart.highCnt = 0;
- }
- } else {
- Uart.syncBit = 0xFFFF; // not set
- // we look for a ...1111111100x11111xxxxxx pattern (the start bit)
- if ((Uart.twoBits & 0xDF00) == 0x1F00) Uart.syncBit = 8; // mask is 11x11111 xxxxxxxx,
- // check for 00x11111 xxxxxxxx
- else if ((Uart.twoBits & 0xEF80) == 0x8F80) Uart.syncBit = 7; // both masks shifted right one bit, left padded with '1'
- else if ((Uart.twoBits & 0xF7C0) == 0xC7C0) Uart.syncBit = 6; // ...
- else if ((Uart.twoBits & 0xFBE0) == 0xE3E0) Uart.syncBit = 5;
- else if ((Uart.twoBits & 0xFDF0) == 0xF1F0) Uart.syncBit = 4;
- else if ((Uart.twoBits & 0xFEF8) == 0xF8F8) Uart.syncBit = 3;
- else if ((Uart.twoBits & 0xFF7C) == 0xFC7C) Uart.syncBit = 2;
- else if ((Uart.twoBits & 0xFFBE) == 0xFE3E) Uart.syncBit = 1;
- if (Uart.syncBit != 0xFFFF) { // found a sync bit
- Uart.startTime = non_real_time?non_real_time:(GetCountSspClk() & 0xfffffff8);
- Uart.startTime -= Uart.syncBit;
- Uart.endTime = Uart.startTime;
- Uart.state = STATE_START_OF_COMMUNICATION;
- }
+ Uart.syncBit = 9999; // not set
+ // we look for a ...xxxx1111111100x11111xxxxxx pattern
+ // (unmodulated, followed by the start bit = 8 '1's followed by 2 '0's, eventually followed by another '0', followed by 5 '1's)
+#define ISO14443A_STARTBIT_MASK 0x007FEF80 // mask is 00000000 01111111 11101111 10000000
+#define ISO14443A_STARTBIT_PATTERN 0x007F8F80 // pattern is 00000000 01111111 10001111 10000000
+ if ((Uart.fourBits & ISO14443A_STARTBIT_MASK) >> 0 == ISO14443A_STARTBIT_PATTERN >> 0) Uart.syncBit = 7;
+ else if ((Uart.fourBits & ISO14443A_STARTBIT_MASK) >> 1 == ISO14443A_STARTBIT_PATTERN >> 1) Uart.syncBit = 6;
+ else if ((Uart.fourBits & ISO14443A_STARTBIT_MASK) >> 2 == ISO14443A_STARTBIT_PATTERN >> 2) Uart.syncBit = 5;
+ else if ((Uart.fourBits & ISO14443A_STARTBIT_MASK) >> 3 == ISO14443A_STARTBIT_PATTERN >> 3) Uart.syncBit = 4;
+ else if ((Uart.fourBits & ISO14443A_STARTBIT_MASK) >> 4 == ISO14443A_STARTBIT_PATTERN >> 4) Uart.syncBit = 3;
+ else if ((Uart.fourBits & ISO14443A_STARTBIT_MASK) >> 5 == ISO14443A_STARTBIT_PATTERN >> 5) Uart.syncBit = 2;
+ else if ((Uart.fourBits & ISO14443A_STARTBIT_MASK) >> 6 == ISO14443A_STARTBIT_PATTERN >> 6) Uart.syncBit = 1;
+ else if ((Uart.fourBits & ISO14443A_STARTBIT_MASK) >> 7 == ISO14443A_STARTBIT_PATTERN >> 7) Uart.syncBit = 0;
+ if (Uart.syncBit != 9999) { // found a sync bit
+ Uart.startTime = non_real_time?non_real_time:(GetCountSspClk() & 0xfffffff8);
+ Uart.startTime -= Uart.syncBit;
+ Uart.endTime = Uart.startTime;
+ Uart.state = STATE_START_OF_COMMUNICATION;
}
} else {
- if (IsMillerModulationNibble1(Uart.twoBits >> Uart.syncBit)) {
- if (IsMillerModulationNibble2(Uart.twoBits >> Uart.syncBit)) { // Modulation in both halves - error
+ if (IsMillerModulationNibble1(Uart.fourBits >> Uart.syncBit)) {
+ if (IsMillerModulationNibble2(Uart.fourBits >> Uart.syncBit)) { // Modulation in both halves - error
UartReset();
} else { // Modulation in first half = Sequence Z = logic "0"
if (Uart.state == STATE_MILLER_X) { // error - must not follow after X
}
}
} else {
- if (IsMillerModulationNibble2(Uart.twoBits >> Uart.syncBit)) { // Modulation second half = Sequence X = logic "1"
+ if (IsMillerModulationNibble2(Uart.fourBits >> Uart.syncBit)) { // Modulation second half = Sequence X = logic "1"
Uart.bitCount++;
Uart.shiftReg = (Uart.shiftReg >> 1) | 0x100; // add a 1 to the shiftreg
Uart.state = STATE_MILLER_X;
return TRUE; // we are finished with decoding the raw data sequence
} else {
UartReset(); // Nothing received - start over
- Uart.highCnt = 1;
}
}
if (Uart.state == STATE_START_OF_COMMUNICATION) { // error - must not follow directly after SOC
UartReset();
- Uart.highCnt = 1;
} else { // a logic "0"
Uart.bitCount++;
Uart.shiftReg = (Uart.shiftReg >> 1); // add a 0 to the shiftreg