From 2178ff4ac1542b6194cbf6bc9e9e3bc4306640ea Mon Sep 17 00:00:00 2001
From: Markus Hitter <mah@jump-ing.de>
Date: Fri, 10 Sep 2010 02:07:50 +0200
Subject: [PATCH] Implement acceleration ramping. Enjoy always smooth rides!

---
 dda.c     | 40 ++++++++++++++++++++++++++++++++++++++++
 dda.h     | 21 +++++++++++++++++++++
 machine.h | 16 ++++++++++++++++
 3 files changed, 77 insertions(+)

diff --git a/dda.c b/dda.c
index 0b098d7..6d409f5 100644
--- a/dda.c
+++ b/dda.c
@@ -270,9 +270,19 @@ void dda_create(DDA *dda, TARGET *target) {
 		}
 		else
 			dda->accel = 0;
+		#else  // #elifdef isn't valid for gcc
+		#ifdef ACCELERATION_RAMPING
+		dda->ramp_steps = dda->total_steps / 2;
+		dda->step_no = 0;
+		// c is initial step time in IOclk ticks
+		dda->c = ACCELERATION_STEEPNESS << 8;
+		dda->c_min = (move_duration / target->F) << 8;
+		dda->n = 1;
+		dda->ramp_state = RAMP_UP;
 		#else
 		dda->c = (move_duration / target->F) << 8;
 		#endif
+		#endif
 	}
 
 	if (debug_flags & DEBUG_DDA)
@@ -411,6 +421,36 @@ void dda_step(DDA *dda) {
 		// else we are already at target speed
 	}
 	#endif
+	#ifdef ACCELERATION_RAMPING
+	// - algorithm courtesy of http://www.embedded.com/columns/technicalinsights/56800129?printable=true
+	// - for simplicity, taking even/uneven number of steps into account dropped
+	// - number of steps moved is always accurate, speed might be one step off
+	switch (dda->ramp_state) {
+	case RAMP_UP:
+	case RAMP_MAX:
+		if (dda->step_no >= dda->ramp_steps) {
+			// RAMP_UP: time to decelerate before reaching maximum speed
+			// RAMP_MAX: time to decelerate
+			dda->ramp_state = RAMP_DOWN;
+			dda->n = -((int32_t)2) - dda->n;
+		}
+		if (dda->ramp_state == RAMP_MAX)
+			break;
+	case RAMP_DOWN:
+		dda->n += 4;
+		// be careful of signedness!
+		dda->c = (int32_t)dda->c - ((int32_t)(dda->c * 2) / dda->n);
+		if (dda->c <= dda->c_min) {
+			// maximum speed reached
+			dda->c = dda->c_min;
+			dda->ramp_state = RAMP_MAX;
+			dda->ramp_steps = dda->total_steps - dda->step_no;
+		}
+		setTimer(dda->c >> 8);
+		break;
+	}
+	dda->step_no++;
+	#endif
 
 	if (did_step) {
 		// we stepped, reset timeout
diff --git a/dda.h b/dda.h
index 78863ce..2f84951 100644
--- a/dda.h
+++ b/dda.h
@@ -6,6 +6,16 @@
 #include	"pinout.h"
 #include	"machine.h"
 
+/*
+	enums
+*/
+// wether we accelerate, run at full speed, break down, etc.
+typedef enum {
+	RAMP_UP,
+	RAMP_MAX,
+	RAMP_DOWN
+} ramp_state_t;
+
 /*
 	types
 */
@@ -66,6 +76,17 @@ typedef struct {
 	uint32_t					end_c;
 	int32_t						n;
 	#endif
+	#ifdef ACCELERATION_RAMPING
+	// start of down-ramp, intitalized with total_steps / 2
+	uint32_t					ramp_steps;
+	// counts actual steps done
+	uint32_t					step_no;
+	// 24.8 fixed point timer value, maximum speed
+	uint32_t					c_min;
+	// tracking variable
+	int32_t						n;
+	ramp_state_t			ramp_state;
+	#endif
 } DDA;
 
 /*
diff --git a/machine.h b/machine.h
index 49a981a..ab6a1e3 100644
--- a/machine.h
+++ b/machine.h
@@ -41,6 +41,22 @@
 // to reach target speed at the end of the movement.
 #define ACCELERATION_REPRAP
 
+// acceleration and deceleration ramping. Each movement starts at
+// (almost) no speed, linearly accelerates to target speed and decelerates
+// just in time to smoothly stop at the target.
+// alternative to ACCELERATION_REPRAP
+//#define ACCELERATION_RAMPING
+// how fast to accelerate when using ACCELERATION_RAMPING
+// smaller values give quicker acceleration
+// valid range = 1 to 8,000,000; 500,000 is a good starting point
+#define ACCELERATION_STEEPNESS	500000
+
+#ifdef ACCELERATION_REPRAP
+#ifdef ACCELERATION_RAMPING
+#error Cant use ACCELERATION_REPRAP and ACCELERATION_RAMPING together.
+#endif
+#endif
+
 // --------------------------------------------------------------------------
 // you shouldn't need to edit something below this line