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/*
* Duet3DFilamentSensor.cpp
*
* Created on: 20 Jul 2017
* Author: David
*/
#include "Duet3DFilamentMonitor.h"
#include "GCodes/GCodeBuffer/GCodeBuffer.h"
#include "Platform.h"
#include "Movement/StepTimer.h"
#include "RepRap.h"
// Constructors
Duet3DFilamentMonitor::Duet3DFilamentMonitor(unsigned int extruder, unsigned int type) noexcept
: FilamentMonitor(extruder, type), overrunErrorCount(0), polarityErrorCount(0)
{
InitReceiveBuffer();
}
void Duet3DFilamentMonitor::InitReceiveBuffer() noexcept
{
edgeCaptureReadPointer = edgeCaptureWritePointer = 1;
edgeCaptures[0] = StepTimer::GetTimerTicks(); // pretend we just had a high-to-low transition
state = RxdState::waitingForStartBit;
}
// ISR for when the pin state changes. It should return true if the ISR wants the commanded extrusion to be fetched.
bool Duet3DFilamentMonitor::Interrupt() noexcept
{
uint32_t now = StepTimer::GetTimerTicks();
bool wantReading = false;
const size_t writePointer = edgeCaptureWritePointer; // capture volatile variable
if ((writePointer + 1) % EdgeCaptureBufferSize != edgeCaptureReadPointer) // if buffer is not full
{
if (GetPort().Read())
{
if ((writePointer & 1) == 0) // low-to-high transitions should occur on odd indices
{
++polarityErrorCount;
return false;
}
if (state == RxdState::waitingForStartBit && writePointer == edgeCaptureReadPointer && !HaveIsrStepsCommanded())
{
wantReading = true; // if this is a possible start bit, ask for the extrusion commanded
}
}
else
{
if ((writePointer & 1) != 0) // high-to-low transitions should occur on even indices
{
++polarityErrorCount;
return false;
}
now -= 40; // partial correction for skew caused by debounce filter on older Duet endstop inputs (measured skew = 74)
}
edgeCaptures[writePointer] = now; // record the time at which this edge was detected
edgeCaptureWritePointer = (writePointer + 1) % EdgeCaptureBufferSize;
}
else
{
++overrunErrorCount;
}
return wantReading;
}
// Call the following regularly to keep the status up to date
Duet3DFilamentMonitor::PollResult Duet3DFilamentMonitor::PollReceiveBuffer(uint16_t& measurement) noexcept
{
// For the Duet3D sensors we need to decode the received data from the transition times recorded in the edgeCaptures array
static constexpr uint32_t BitsPerSecond = 1000; // the nominal bit rate that the data is transmitted at
static constexpr uint32_t NominalBitLength = StepTimer::StepClockRate/BitsPerSecond; // the nominal bit length in step clocks
static constexpr uint32_t MinBitLength = (NominalBitLength * 10)/13; // allow 30% clock speed tolerance
static constexpr uint32_t MaxBitLength = (NominalBitLength * 13)/10; // allow 30% clock speed tolerance
static constexpr uint32_t ErrorRecoveryDelayBits = 8; // before a start bit we want the line to be low for this long
static constexpr uint32_t ErrorRecoveryTime = NominalBitLength * ErrorRecoveryDelayBits;
bool again;
do
{
again = false;
const size_t writePointer = edgeCaptureWritePointer; // capture volatile variable
const uint32_t now = StepTimer::GetTimerTicks();
switch (state)
{
case RxdState::waitingForStartBit:
if (writePointer != edgeCaptureReadPointer) // if we have recorded any new edges
{
if ((edgeCaptureReadPointer & 1u) == 0) // if we are out of sync (this is normal when the last stuffing bit was a 1)
{
edgeCaptureReadPointer = (edgeCaptureReadPointer + 1u) % EdgeCaptureBufferSize;
again = true;
}
else
{
if (edgeCaptures[edgeCaptureReadPointer] - edgeCaptures[(edgeCaptureReadPointer - 1) % EdgeCaptureBufferSize] < ErrorRecoveryTime)
{
// The input line has not been idle for long enough before the start bit
edgeCaptureReadPointer = (edgeCaptureReadPointer + 1u) % EdgeCaptureBufferSize; // ignore this start bit
state = RxdState::errorRecovery1;
again = true;
}
else
{
state = RxdState::waitingForEndOfStartBit;
again = true;
}
}
}
break;
case RxdState::waitingForEndOfStartBit:
// This state must time out because while we are in it, comparison of filament extruded is suspended
if ((writePointer - edgeCaptureReadPointer) % EdgeCaptureBufferSize >= 2)
{
// Check for a valid start bit
lastBitChangeIndex = (edgeCaptureReadPointer + 1u) % EdgeCaptureBufferSize;
startBitLength = edgeCaptures[lastBitChangeIndex] - edgeCaptures[edgeCaptureReadPointer];
edgeCaptureReadPointer = lastBitChangeIndex;
if (startBitLength >= MinBitLength && startBitLength <= MaxBitLength)
{
valueBeingAssembled = 0;
nibblesAssembled = 0;
state = RxdState::waitingForNibble;
again = true;
}
else
{
// Start bit too long or too short
state = RxdState::errorRecovery2;
again = true;
}
}
else if (now - edgeCaptures[edgeCaptureReadPointer] > MaxBitLength) // check for timeout
{
edgeCaptureReadPointer = (edgeCaptureReadPointer + 1u) % EdgeCaptureBufferSize;
state = RxdState::errorRecovery2;
again = true;
}
break;
case RxdState::waitingForNibble:
// This state must time out because while we are in it, comparison of filament extruded is suspended
{
const uint32_t nibbleStartTime = edgeCaptures[lastBitChangeIndex];
if (now - nibbleStartTime > (13 * startBitLength)/2)
{
// 6.5 bit times have passed since the start of the bit that preceded the current nibble, so we should have a complete nibble and the following stuffing bit
uint32_t samplePoint = (startBitLength * 3)/2; // sampling time after the end of the start bit for bit 7 (MSB)
uint8_t currentNibble = 0;
size_t nextBitChangeIndex = (lastBitChangeIndex + 1u) % EdgeCaptureBufferSize;
for (uint8_t numBits = 0; numBits < 5; ++numBits)
{
if (nextBitChangeIndex != edgeCaptureWritePointer && edgeCaptures[nextBitChangeIndex] - nibbleStartTime < samplePoint)
{
lastBitChangeIndex = nextBitChangeIndex;
nextBitChangeIndex = (lastBitChangeIndex + 1u) % EdgeCaptureBufferSize;
if (nextBitChangeIndex != writePointer && edgeCaptures[nextBitChangeIndex] - nibbleStartTime < samplePoint)
{
// We recorded two edges within one sample period
edgeCaptureReadPointer = nextBitChangeIndex;
state = RxdState::errorRecovery3;
again = true;
break;
}
}
currentNibble <<= 1;
currentNibble |= (uint8_t)(lastBitChangeIndex & 1u);
samplePoint += startBitLength;
}
if (state != RxdState::waitingForNibble)
{
break;
}
// The 5th bit we received should be the inverse of the 4th bit
if ((((currentNibble >> 1u) ^ currentNibble) & 0x01u) == 0)
{
edgeCaptureReadPointer = nextBitChangeIndex;
state = RxdState::errorRecovery4;
again = true;
break;
}
currentNibble >>= 1;
valueBeingAssembled = (valueBeingAssembled << 4) | currentNibble;
++nibblesAssembled;
if (nibblesAssembled == 4) // if we have a complete 16-bit word
{
edgeCaptureReadPointer = nextBitChangeIndex; // ready for a new word
measurement = valueBeingAssembled;
state = RxdState::waitingForStartBit;
return PollResult::complete;
}
again = true;
}
}
break;
default: // error recovery states
if (reprap.Debug(moduleFilamentSensors))
{
debugPrintf("Fil err %u\n", (unsigned int)state);
}
state = RxdState::waitingForStartBit;
return PollResult::error;
}
} while (again);
return PollResult::incomplete;
}
// Return true if we are on the process of receiving data form the filament monitor
bool Duet3DFilamentMonitor::IsReceiving() const noexcept
{
return state == RxdState::waitingForEndOfStartBit || state == RxdState::waitingForNibble;
}
// Return true if we are waiting for a start bit
bool Duet3DFilamentMonitor::IsWaitingForStartBit() const noexcept
{
return state == RxdState::waitingForStartBit;
}
// End
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