From 9b010e65eeee5479423d7356c74b3e338d89e6af Mon Sep 17 00:00:00 2001
From: wurstnase <wurstnase.reprap@gmail.com>
Date: Fri, 24 Jun 2016 20:04:24 +0200
Subject: [PATCH] Introduce M221 aka flow-control.

Now it is possible to control the extruders flow.

  M221 S100 = 100% of the extruders steps
  M221 S90  = 90% of the extruders steps

M221 is also used in other firmwares for this. Also a lot of
hosts, like Octoprint and Pronterface using this M-Code for
this behaviour.
---
 dda.c           | 7 +++++++
 dda.h           | 1 +
 gcode_process.c | 7 +++++++
 3 files changed, 15 insertions(+)

diff --git a/dda.c b/dda.c
index ec16d12..0884263 100644
--- a/dda.c
+++ b/dda.c
@@ -110,6 +110,8 @@ void dda_init(void) {
 	// set up default feedrate
 	if (startpoint.F == 0)
 		startpoint.F = next_target.target.F = SEARCH_FEEDRATE_Z;
+  if (startpoint.e_multiplier == 0)
+    startpoint.e_multiplier = next_target.target.e_multiplier = 100;
 }
 
 /*! Distribute a new startpoint to DDA's internal structures without any movement.
@@ -216,6 +218,11 @@ void dda_create(DDA *dda, TARGET *target) {
   // type, but are subject to other special handling.
   steps[E] = um_to_steps(target->axis[E], E);
 
+  // Apply extrusion multiplier.
+  steps[E] *= target->e_multiplier;
+  steps[E] += 50;
+  steps[E] /= 100;
+
   if ( ! target->e_relative) {
     int32_t delta_steps;
 
diff --git a/dda.h b/dda.h
index 10a5ea3..4eaef1a 100644
--- a/dda.h
+++ b/dda.h
@@ -41,6 +41,7 @@ typedef struct {
   axes_int32_t axis;
   uint32_t  F;
 
+  uint8_t   e_multiplier;
   uint8_t   e_relative        :1; ///< bool: e axis relative? Overrides all_relative
 } TARGET;
 
diff --git a/gcode_process.c b/gcode_process.c
index 79493e9..b87f2d5 100644
--- a/gcode_process.c
+++ b/gcode_process.c
@@ -793,6 +793,13 @@ void process_gcode_command() {
 				#endif
 				break;
 
+      case 221:
+        //? --- M221: Control the extruders flow ---
+        if ( ! next_target.seen_S)
+          break;
+        next_target.target.e_multiplier = next_target.S;
+        break;
+
       #ifdef DEBUG
 			case 240:
 				//? --- M240: echo off ---