attempt to implement search ROM algorithm (doesn't work at this time)
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b236a684ca
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68f4fce878
187
OneWireIO.ino
187
OneWireIO.ino
@ -15,6 +15,11 @@
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#define BitZeroMinDuration 20
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#define BitZeroMaxDuration 75
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#define SendBitDuration 30
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const byte InvalidBit = (byte)-1;
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const byte IncompleteBit = (byte)-2;
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SerialChannel debug("debug");
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Pin owPin(OWPin);
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@ -27,9 +32,16 @@ enum OwStatus
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OS_Presence,
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OS_AfterPresence,
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OS_WaitCommand,
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OS_SearchRom,
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};
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OwStatus status;
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byte owROM[8] = { 0xE2, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00 };
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byte searchROMCurrentByte = 0;
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byte searchROMCurrentBit = 0;
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bool searchROMSendingInverse = false;
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bool searchROMReadingMasterResponseBit = false;
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void owPullLow()
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{
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owPin.outputMode();
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@ -112,6 +124,7 @@ void owError(const char* message)
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{
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debug.append(message);
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led.writeHigh();
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status = OS_WaitReset;
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}
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void owResetError()
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@ -151,6 +164,7 @@ void onewireInterrupt(void)
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status = OS_WaitCommand;
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receivingByte = 0;
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receivingBitPos = 0;
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bitStart = (unsigned long)-1;
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if (state)
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{
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@ -162,55 +176,152 @@ void onewireInterrupt(void)
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// read bytes
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if (status == OS_WaitCommand)
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{
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if (!state)
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byte bit = interpretReceivedEdgeAsBit(state, now);
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if (bit != IncompleteBit)
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{
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// master just pulled low, this is a bit start
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//debug.SC_APPEND_STR_TIME("bit start", now);
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bitStart = now;
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}
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else
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{
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if (bitStart == (unsigned long)-1)
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{
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//owError("Invalid read sequence");
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//return;
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// we missed the falling edge, we emulate one here (this can happen if handling of rising edge interrupt takes too long)
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bitStart = now;
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}
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// master released the line, we interpret it as a bit 1 or 0 depending on timing
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unsigned long bitLength = now - bitStart;
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bitStart = (unsigned long)-1;
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if (bitLength < BitZeroMinDuration)
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{
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// received bit = 1
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//debug.SC_APPEND_STR_TIME("received bit 1", now);
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receivingByte |= (1 << receivingBitPos);
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++receivingBitPos;
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}
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else if (bitLength < BitZeroMaxDuration)
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{
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// received bit = 0
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//debug.SC_APPEND_STR_TIME("received bit 0", now);
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++receivingBitPos;
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}
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else
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{
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// this is not a valid bit
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owError("Invalid read timing");
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if (bit == InvalidBit)
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return;
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}
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receivingByte |= (bit << receivingBitPos);
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++receivingBitPos;
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if (receivingBitPos == 8)
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{
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debug.SC_APPEND_STR_INT("received byte", (long)receivingByte);
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if (status == OS_WaitCommand && receivingByte == 0xF0)
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{
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status = OS_SearchRom;
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searchROMReadingMasterResponseBit = false;
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searchROMSendingInverse = false;
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searchROMCurrentByte = 0;
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searchROMCurrentBit = 0;
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return;
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}
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receivingBitPos = 0;
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receivingByte = 0;
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}
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}
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}
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if (status == OS_SearchRom)
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{
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byte currentByte = owROM[searchROMCurrentByte];
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bool currentBit = bitRead(currentByte, searchROMCurrentBit);
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if (searchROMReadingMasterResponseBit)
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{
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byte bit = interpretReceivedEdgeAsBit(state, now);
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if (bit != IncompleteBit)
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{
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searchROMReadingMasterResponseBit = false;
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if (bit == InvalidBit)
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return;
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if ((bit == 1) != currentBit)
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{
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debug.SC_APPEND_STR_TIME("Master didn't send our bit, leaving ROM search", now);
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status = OS_WaitReset;
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}
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}
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}
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else
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{
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if (!state)
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{
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// master is pulling low, we must send our bit
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bool bitToSend = searchROMSendingInverse ? !currentBit : currentBit;
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sendBit(bitToSend);
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if (bitToSend)
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debug.SC_APPEND_STR_TIME("Sent ROM search bit : 1", now);
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else
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debug.SC_APPEND_STR_TIME("Sent ROM search bit : 0", now);
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if (searchROMSendingInverse)
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{
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searchROMSendingInverse = false;
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searchROMReadingMasterResponseBit = true;
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}
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else
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{
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searchROMSendingInverse = true;
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}
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if (searchROMCurrentBit == 8)
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{
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++searchROMCurrentByte;
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searchROMCurrentBit = 0;
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debug.SC_APPEND_STR_TIME("sent another ROM byte", now);
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}
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if (searchROMCurrentByte == 8)
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{
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searchROMCurrentByte = 0;
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status = OS_WaitReset;
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debug.SC_APPEND_STR_TIME("ROM sent entirely", now);
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}
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}
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else
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{
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debug.SC_APPEND_STR_TIME("Search ROM : seen rising edge", now);
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}
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}
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}
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}
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byte interpretReceivedEdgeAsBit(bool wireState, unsigned long now)
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{
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if (!wireState)
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{
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// master just pulled low, this is a bit start
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//debug.SC_APPEND_STR_TIME("bit start", now);
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bitStart = now;
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return IncompleteBit;
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}
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else
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{
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if (bitStart == (unsigned long)-1)
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{
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//owError("Invalid read sequence");
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//return InvalidBit;
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// we missed the falling edge, we emulate one here (this can happen if handling of rising edge interrupt takes too long)
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bitStart = now;
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}
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// master released the line, we interpret it as a bit 1 or 0 depending on timing
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unsigned long bitLength = now - bitStart;
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bitStart = (unsigned long)-1;
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if (bitLength < BitZeroMinDuration)
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{
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// received bit = 1
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//debug.SC_APPEND_STR_TIME("received bit 1", now);
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return 1;
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}
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else if (bitLength < BitZeroMaxDuration)
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{
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// received bit = 0
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//debug.SC_APPEND_STR_TIME("received bit 0", now);
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return 0;
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}
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else
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{
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// this is not a valid bit
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owError("Invalid read timing");
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return InvalidBit;
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}
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}
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}
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void sendBit(bool bit)
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{
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if (!bit)
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{
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owPullLow();
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delayMicroseconds(SendBitDuration);
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owRelease();
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}
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}
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void beginPresence()
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