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@ -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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@ -161,19 +175,115 @@ 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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byte bit = interpretReceivedEdgeAsBit(state, now); |
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if (bit != IncompleteBit) |
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{ |
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if (bit == InvalidBit) |
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return; |
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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;
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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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@ -187,29 +297,30 @@ void onewireInterrupt(void)
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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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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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++receivingBitPos; |
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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; |
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return InvalidBit; |
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} |
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} |
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} |
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if (receivingBitPos == 8) |
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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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debug.SC_APPEND_STR_INT("received byte", (long)receivingByte); |
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receivingBitPos = 0; |
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receivingByte = 0; |
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} |
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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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