typedef struct DecodeReader {
enum {
STATE_READER_UNSYNCD,
+ STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF,
STATE_READER_AWAIT_1ST_RISING_EDGE_OF_SOF,
STATE_READER_AWAIT_2ND_FALLING_EDGE_OF_SOF,
STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF,
{
switch (DecodeReader->state) {
case STATE_READER_UNSYNCD:
+ // wait for unmodulated carrier
+ if (bit) {
+ DecodeReader->state = STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF;
+ }
+ break;
+
+ case STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF:
if (!bit) {
// we went low, so this could be the beginning of a SOF
DecodeReader->posCount = 1;
DecodeReader->posCount++;
if (bit) { // detected rising edge
if (DecodeReader->posCount < 4) { // rising edge too early (nominally expected at 5)
- DecodeReaderReset(DecodeReader);
+ DecodeReader->state = STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF;
} else { // SOF
DecodeReader->state = STATE_READER_AWAIT_2ND_FALLING_EDGE_OF_SOF;
}
DecodeReader->state = STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF;
} else if (DecodeReader->posCount < 28) { // falling edge too early (nominally expected at 29 latest)
DecodeReaderReset(DecodeReader);
- } else { // SOF for 1 out of 4 coding
+ } else { // SOF for 1 out of 256 coding
DecodeReader->Coding = CODING_1_OUT_OF_256;
DecodeReader->state = STATE_READER_AWAIT_2ND_RISING_EDGE_OF_SOF;
}
} else {
if (DecodeReader->posCount > 29) { // stayed high for too long
- DecodeReaderReset(DecodeReader);
+ DecodeReader->state = STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF;
} else {
// do nothing, keep waiting
}
if (bit) { // detected rising edge
if (DecodeReader->Coding == CODING_1_OUT_OF_256) {
if (DecodeReader->posCount < 32) { // rising edge too early (nominally expected at 33)
- DecodeReaderReset(DecodeReader);
+ DecodeReader->state = STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF;
} else {
DecodeReader->posCount = 1;
DecodeReader->bitCount = 0;
}
} else { // CODING_1_OUT_OF_4
if (DecodeReader->posCount < 24) { // rising edge too early (nominally expected at 25)
- DecodeReaderReset(DecodeReader);
+ DecodeReader->state = STATE_READER_AWAIT_1ST_FALLING_EDGE_OF_SOF;
} else {
+ DecodeReader->posCount = 1;
DecodeReader->state = STATE_READER_AWAIT_END_OF_SOF_1_OUT_OF_4;
}
}
} else {
if (DecodeReader->Coding == CODING_1_OUT_OF_256) {
if (DecodeReader->posCount > 34) { // signal stayed low for too long
- DecodeReaderReset(DecodeReader);
+ DecodeReaderReset(DecodeReader);
} else {
// do nothing, keep waiting
}
} else { // CODING_1_OUT_OF_4
if (DecodeReader->posCount > 26) { // signal stayed low for too long
- DecodeReaderReset(DecodeReader);
+ DecodeReaderReset(DecodeReader);
} else {
// do nothing, keep waiting
}
case STATE_READER_AWAIT_END_OF_SOF_1_OUT_OF_4:
DecodeReader->posCount++;
if (bit) {
- if (DecodeReader->posCount == 33) {
+ if (DecodeReader->posCount == 9) {
DecodeReader->posCount = 1;
DecodeReader->bitCount = 0;
DecodeReader->byteCount = 0;
break;
case STATE_READER_RECEIVE_DATA_1_OUT_OF_4:
+ bit = !!bit;
DecodeReader->posCount++;
if (DecodeReader->posCount == 1) {
DecodeReader->sum1 = bit;
}
if (DecodeReader->posCount == 8) {
DecodeReader->posCount = 0;
- int corr10 = DecodeReader->sum1 - DecodeReader->sum2;
- int corr01 = DecodeReader->sum2 - DecodeReader->sum1;
- int corr11 = (DecodeReader->sum1 + DecodeReader->sum2) / 2;
- if (corr01 > corr11 && corr01 > corr10) { // EOF
+ if (DecodeReader->sum1 <= 1 && DecodeReader->sum2 >= 3) { // EOF
LED_B_OFF(); // Finished receiving
DecodeReaderReset(DecodeReader);
if (DecodeReader->byteCount != 0) {
return true;
}
}
- if (corr10 > corr11) { // detected a 2bit position
+ if (DecodeReader->sum1 >= 3 && DecodeReader->sum2 <= 1) { // detected a 2bit position
DecodeReader->shiftReg >>= 2;
DecodeReader->shiftReg |= (DecodeReader->bitCount << 6);
}
break;
case STATE_READER_RECEIVE_DATA_1_OUT_OF_256:
+ bit = !!bit;
DecodeReader->posCount++;
if (DecodeReader->posCount == 1) {
DecodeReader->sum1 = bit;
}
if (DecodeReader->posCount == 8) {
DecodeReader->posCount = 0;
- int corr10 = DecodeReader->sum1 - DecodeReader->sum2;
- int corr01 = DecodeReader->sum2 - DecodeReader->sum1;
- int corr11 = (DecodeReader->sum1 + DecodeReader->sum2) / 2;
- if (corr01 > corr11 && corr01 > corr10) { // EOF
+ if (DecodeReader->sum1 <= 1 && DecodeReader->sum2 >= 3) { // EOF
LED_B_OFF(); // Finished receiving
DecodeReaderReset(DecodeReader);
if (DecodeReader->byteCount != 0) {
return true;
}
}
- if (corr10 > corr11) { // detected the bit position
+ if (DecodeReader->sum1 >= 3 && DecodeReader->sum2 <= 1) { // detected the bit position
DecodeReader->shiftReg = DecodeReader->bitCount;
}
if (DecodeReader->bitCount == 255) { // we have a full byte