Feature / Configurable Grace Period for Starting into Moves (#471)

* Added M595 Rnn word to set the grace period, that is waited out before starting moves. The R word is given in milliseconds and it controls the idle time after receiving the last move command to process.
This will make sure fine-grained move sequences will be received in full and can be look-ahead-planned properly, right to the end. This option has been introduced after it was demonstrated that Duet would rush into premature deceleration on fine-grained interpolation move sequences send from OpenPnP. De to their nature, these motion sequences typically need to be look-ahead-planned in full, otherwise they will be degraded.
Note that M400 (and others) will release the motion sequence immediately. A motion sequence closed with M400 will therefore incur no additional wait time (once the commands have been received).

* Changes, as indicated by dc42

4 files changed, 16 insertions, 4 deletions

diff --git a/src/Movement/DDARing.cpp b/src/Movement/DDARing.cpp
index dad6f4e8..100445d4 100644
--- a/src/Movement/DDARing.cpp
+++ b/src/Movement/DDARing.cpp
@@ -18,7 +18,7 @@
 constexpr uint32_t UsualMinimumPreparedTime = StepTimer::StepClockRate/10;			// 100ms
 constexpr uint32_t AbsoluteMinimumPreparedTime = StepTimer::StepClockRate/20;		// 50ms
 
-DDARing::DDARing() noexcept : scheduledMoves(0), completedMoves(0), numHiccups(0)
+DDARing::DDARing() noexcept : gracePeriod(0), scheduledMoves(0), completedMoves(0), numHiccups(0)
 {
 }
 
@@ -99,6 +99,7 @@ GCodeResult DDARing::ConfigureMovementQueue(GCodeBuffer& gb, const StringRef& re
 	uint32_t numDdasWanted = 0, numDMsWanted = 0;
 	gb.TryGetUIValue('P', numDdasWanted, seen);
 	gb.TryGetUIValue('S', numDMsWanted, seen);
+	gb.TryGetUIValue('R', gracePeriod, seen);
 	if (seen)
 	{
 		if (!reprap.GetGCodes().LockMovementAndWaitForStandstill(gb))
@@ -143,7 +144,7 @@ GCodeResult DDARing::ConfigureMovementQueue(GCodeBuffer& gb, const StringRef& re
 	}
 	else
 	{
-		reply.printf("DDAs %u, DMs %u", numDdasInRing, DriveMovement::NumCreated());
+		reply.printf("DDAs %u, DMs %u, GracePeriod %" PRIu32, numDdasInRing, DriveMovement::NumCreated(), gracePeriod);
 	}
 	return GCodeResult::ok;
 }
@@ -357,6 +358,11 @@ bool DDARing::IsIdle() const noexcept
 	return currentDda == nullptr && getPointer->GetState() == DDA::empty;
 }
 
+uint32_t DDARing::GetGracePeriod() const noexcept
+{
+	return gracePeriod;
+}
+
 // Try to push some babystepping through the lookahead queue, returning the amount pushed
 float DDARing::PushBabyStepping(size_t axis, float amount) noexcept
 {
diff --git a/src/Movement/DDARing.h b/src/Movement/DDARing.h
index d386a176..f0725c27 100644
--- a/src/Movement/DDARing.h
+++ b/src/Movement/DDARing.h
@@ -31,6 +31,7 @@ public:
 
 	void Spin(uint8_t simulationMode, bool shouldStartMove) noexcept SPEED_CRITICAL;	// Try to process moves in the ring
 	bool IsIdle() const noexcept;														// Return true if this DDA ring is idle
+	uint32_t GetGracePeriod() const noexcept;											// Return the minimum idle time, before we should start a move. Better to have a few moves in the queue so that we can do lookahead
 
 	float PushBabyStepping(size_t axis, float amount) noexcept;							// Try to push some babystepping through the lookahead queue, returning the amount pushed
 
@@ -106,6 +107,7 @@ private:
 	volatile int32_t liveEndPoints[MaxAxesPlusExtruders];						// The XYZ endpoints of the last completed move in motor coordinates
 
 	unsigned int numDdasInRing;
+	uint32_t gracePeriod;														// The minimum idle time, before we should start a move. Better to have a few moves in the queue so that we can do lookahead
 
 	uint32_t scheduledMoves;													// Move counters for the code queue
 	volatile uint32_t completedMoves;											// This one is modified by an ISR, hence volatile
diff --git a/src/Movement/Move.cpp b/src/Movement/Move.cpp
index e5504fbb..4b1f5d63 100644
--- a/src/Movement/Move.cpp
+++ b/src/Movement/Move.cpp
@@ -195,6 +195,7 @@ void Move::Init() noexcept
 	moveState = MoveState::idle;
 	lastStateChangeTime = millis();
 	idleCount = 0;
+	idleStartTime = lastStateChangeTime;
 
 	simulationMode = 0;
 	longestGcodeWaitInterval = 0;
@@ -284,11 +285,12 @@ void Move::Spin() noexcept
 
 					if (mainDDARing.AddStandardMove(nextMove, !IsRawMotorMove(nextMove.moveType)))
 					{
+						const uint32_t now = millis();
 						idleCount = 0;
+						idleStartTime = now;
 						if (moveState == MoveState::idle || moveState == MoveState::timing)
 						{
 							moveState = MoveState::collecting;
-							const uint32_t now = millis();
 							const uint32_t timeWaiting = now - lastStateChangeTime;
 							if (timeWaiting > longestGcodeWaitInterval)
 							{
@@ -302,7 +304,8 @@ void Move::Spin() noexcept
 		}
 	}
 
-	mainDDARing.Spin(simulationMode, idleCount > 10);	// let the DDA ring process moves. Better to have a few moves in the queue so that we can do lookahead, hence the test on idleCount.
+	// let the DDA ring process moves. Better to have a few moves in the queue so that we can do lookahead, hence the test on idleCount and idleTime.
+	mainDDARing.Spin(simulationMode, idleCount > 10 && millis() - idleStartTime >= mainDDARing.GetGracePeriod());
 
 #if SUPPORT_ASYNC_MOVES
 	if (auxMoveAvailable && auxDDARing.CanAddMove())
diff --git a/src/Movement/Move.h b/src/Movement/Move.h
index 60a49235..5f01e390 100644
--- a/src/Movement/Move.h
+++ b/src/Movement/Move.h
@@ -250,6 +250,7 @@ private:
 
 	unsigned int jerkPolicy;							// When we allow jerk
 	unsigned int idleCount;								// The number of times Spin was called and had no new moves to process
+	uint32_t idleStartTime;								// the time when we started to idle
 	uint32_t longestGcodeWaitInterval;					// the longest we had to wait for a new GCode
 
 	float tangents[3]; 									// Axis compensation - 90 degrees + angle gives angle between axes