From 47024c765018d4d6a59f13435ac27d9d7854f597 Mon Sep 17 00:00:00 2001
From: Jan Roters <jroters@gmail.com>
Date: Tue, 4 May 2021 14:53:01 +0200
Subject: [PATCH 1/3] Added inverted PWM signal (see #22)

---
 grbl/config.h          | 13 +++++++++----
 grbl/spindle_control.c | 40 ++++++++++++++++++++++++++++++++++------
 2 files changed, 43 insertions(+), 10 deletions(-)

diff --git a/grbl/config.h b/grbl/config.h
index f48d958..0fe4725 100644
--- a/grbl/config.h
+++ b/grbl/config.h
@@ -102,12 +102,12 @@
 // on separate pin, but homed in one cycle. Also, it should be noted that the function of hard limits
 // will not be affected by pin sharing.
 // NOTE: Defaults are set for a traditional 3-axis CNC machine. Z-axis first to clear, followed by X & Y.
-#define HOMING_CYCLE_0 (1<<Z_AXIS)                // REQUIRED: First move Z to clear workspace.
-#define HOMING_CYCLE_1 ((1<<X_AXIS)|(1<<Y_AXIS))  // OPTIONAL: Then move X,Y at the same time.
+//#define HOMING_CYCLE_0 (1<<Z_AXIS)                // REQUIRED: First move Z to clear workspace.
+//#define HOMING_CYCLE_1 ((1<<X_AXIS)|(1<<Y_AXIS))  // OPTIONAL: Then move X,Y at the same time.
 // #define HOMING_CYCLE_2                         // OPTIONAL: Uncomment and add axes mask to enable
 
 // NOTE: The following are two examples to setup homing for 2-axis machines.
-// #define HOMING_CYCLE_0 ((1<<X_AXIS)|(1<<Y_AXIS))  // NOT COMPATIBLE WITH COREXY: Homes both X-Y in one cycle. 
+#define HOMING_CYCLE_0 ((1<<X_AXIS)|(1<<Y_AXIS))  // NOT COMPATIBLE WITH COREXY: Homes both X-Y in one cycle. 
 
 // #define HOMING_CYCLE_0 (1<<X_AXIS)  // COREXY COMPATIBLE: First home X
 // #define HOMING_CYCLE_1 (1<<Y_AXIS)  // COREXY COMPATIBLE: Then home Y
@@ -126,7 +126,7 @@
 // After homing, Grbl will set by default the entire machine space into negative space, as is typical
 // for professional CNC machines, regardless of where the limit switches are located. Uncomment this
 // define to force Grbl to always set the machine origin at the homed location despite switch orientation.
-// #define HOMING_FORCE_SET_ORIGIN // Uncomment to enable.
+#define HOMING_FORCE_SET_ORIGIN // Uncomment to enable.
 
 // Number of blocks Grbl executes upon startup. These blocks are stored in EEPROM, where the size
 // and addresses are defined in settings.h. With the current settings, up to 2 startup blocks may
@@ -210,6 +210,11 @@
 // uncomment the config option USE_SPINDLE_DIR_AS_ENABLE_PIN below.
 // #define INVERT_SPINDLE_ENABLE_PIN // Default disabled. Uncomment to enable.
 
+// Inverts the PWM signal of the spindle. This can be used, if the inverter of the spindle requires 
+// inverted speed signals. Another example are some power supplies of the K40 lasers which fire the laser
+// at 0V and disable them at 5V.
+// #define INVERT_SPINDLE_PWM // Default disabled. Uncomment to enable.
+
 // Inverts the selected coolant pin from low-disabled/high-enabled to low-enabled/high-disabled. Useful
 // for some pre-built electronic boards.
 // #define INVERT_COOLANT_FLOOD_PIN // Default disabled. Uncomment to enable.
diff --git a/grbl/spindle_control.c b/grbl/spindle_control.c
index 550b752..17e65f0 100644
--- a/grbl/spindle_control.c
+++ b/grbl/spindle_control.c
@@ -26,6 +26,14 @@
   static float pwm_gradient; // Precalulated value to speed up rpm to PWM conversions.
 #endif
 
+static void enable_pwm() {
+  SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT);
+}
+
+static void disable_pwm() {
+  SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); 
+}
+
 
 void spindle_init()
 {
@@ -56,6 +64,7 @@ void spindle_init()
 
 uint8_t spindle_get_state()
 {
+  // TODO add INVERT_SPINDLE_PWM handling
   #ifdef VARIABLE_SPINDLE
     #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
       // No spindle direction output pin. 
@@ -98,7 +107,12 @@ uint8_t spindle_get_state()
 void spindle_stop()
 {
   #ifdef VARIABLE_SPINDLE
-    SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); // Disable PWM. Output voltage is zero.
+    #ifdef INVERT_SPINDLE_PWM
+      enable_pwm(); // Enable PWM with full force. Output voltage is 5V.
+      SPINDLE_OCR_REGISTER = SPINDLE_PWM_MAX_VALUE; // Set PWM output level.
+    #else
+      disable_pwm(); // Disable PWM. Output voltage is zero.
+    #endif
     #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
       #ifdef INVERT_SPINDLE_ENABLE_PIN
         SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);  // Set pin to high
@@ -121,12 +135,18 @@ void spindle_stop()
   // and stepper ISR. Keep routine small and efficient.
   void spindle_set_speed(uint8_t pwm_value)
   {
-    SPINDLE_OCR_REGISTER = pwm_value; // Set PWM output level.
+    uint8_t corr_pwm_value;
+    #ifdef INVERT_SPINDLE_PWM
+      corr_pwm_value = 255-pwm_value;
+    #else
+      corr_pwm_value =  = pwm_value;
+    #endif
+    SPINDLE_OCR_REGISTER = corr_pwm_value;
     #ifdef SPINDLE_ENABLE_OFF_WITH_ZERO_SPEED
       if (pwm_value == SPINDLE_PWM_OFF_VALUE) {
         spindle_stop();
       } else {
-        SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT); // Ensure PWM output is enabled.
+        enable_pwm(); // Ensure PWM output is enabled.
         #ifdef INVERT_SPINDLE_ENABLE_PIN
           SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT);
         #else
@@ -134,11 +154,19 @@ void spindle_stop()
         #endif
       }
     #else
-      if (pwm_value == SPINDLE_PWM_OFF_VALUE) {
-        SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); // Disable PWM. Output voltage is zero.
+    #ifdef INVERT_SPINDLE_PWM
+      if (pwm_value == SPINDLE_PWM_MAX_VALUE) {
+        disable_pwm(); // Disable PWM. Output voltage is zero.
       } else {
-        SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT); // Ensure PWM output is enabled.
+        enable_pwm(); // Ensure PWM output is enabled.
       }
+    #else
+      if (pwm_value == SPINDLE_PWM_OFF_VALUE) {
+        disable_pwm(); // Disable PWM. Output voltage is zero.
+      } else {
+        enable_pwm(); // Ensure PWM output is enabled.
+      }
+      #endif
     #endif
   }
 

From 61d40867ac13dd9e0689ce06b8efc6a9bd3b261a Mon Sep 17 00:00:00 2001
From: Jan Roters <jroters@gmail.com>
Date: Fri, 7 May 2021 11:41:26 +0200
Subject: [PATCH 2/3] Accidentally changed some defaults in config.h

---
 grbl/config.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/grbl/config.h b/grbl/config.h
index 0fe4725..1863613 100644
--- a/grbl/config.h
+++ b/grbl/config.h
@@ -102,12 +102,12 @@
 // on separate pin, but homed in one cycle. Also, it should be noted that the function of hard limits
 // will not be affected by pin sharing.
 // NOTE: Defaults are set for a traditional 3-axis CNC machine. Z-axis first to clear, followed by X & Y.
-//#define HOMING_CYCLE_0 (1<<Z_AXIS)                // REQUIRED: First move Z to clear workspace.
-//#define HOMING_CYCLE_1 ((1<<X_AXIS)|(1<<Y_AXIS))  // OPTIONAL: Then move X,Y at the same time.
+#define HOMING_CYCLE_0 (1<<Z_AXIS)                // REQUIRED: First move Z to clear workspace.
+#define HOMING_CYCLE_1 ((1<<X_AXIS)|(1<<Y_AXIS))  // OPTIONAL: Then move X,Y at the same time.
 // #define HOMING_CYCLE_2                         // OPTIONAL: Uncomment and add axes mask to enable
 
 // NOTE: The following are two examples to setup homing for 2-axis machines.
-#define HOMING_CYCLE_0 ((1<<X_AXIS)|(1<<Y_AXIS))  // NOT COMPATIBLE WITH COREXY: Homes both X-Y in one cycle. 
+// #define HOMING_CYCLE_0 ((1<<X_AXIS)|(1<<Y_AXIS))  // NOT COMPATIBLE WITH COREXY: Homes both X-Y in one cycle. 
 
 // #define HOMING_CYCLE_0 (1<<X_AXIS)  // COREXY COMPATIBLE: First home X
 // #define HOMING_CYCLE_1 (1<<Y_AXIS)  // COREXY COMPATIBLE: Then home Y
@@ -126,7 +126,7 @@
 // After homing, Grbl will set by default the entire machine space into negative space, as is typical
 // for professional CNC machines, regardless of where the limit switches are located. Uncomment this
 // define to force Grbl to always set the machine origin at the homed location despite switch orientation.
-#define HOMING_FORCE_SET_ORIGIN // Uncomment to enable.
+// #define HOMING_FORCE_SET_ORIGIN // Uncomment to enable.
 
 // Number of blocks Grbl executes upon startup. These blocks are stored in EEPROM, where the size
 // and addresses are defined in settings.h. With the current settings, up to 2 startup blocks may

From fb06651a9702be0a2dd98d07be9cf9b55ef4720b Mon Sep 17 00:00:00 2001
From: Jan Roters <jroters@gmail.com>
Date: Fri, 7 May 2021 11:47:49 +0200
Subject: [PATCH 3/3] Removed TODO since there is no need to change anything

---
 grbl/spindle_control.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/grbl/spindle_control.c b/grbl/spindle_control.c
index 17e65f0..6b07dac 100644
--- a/grbl/spindle_control.c
+++ b/grbl/spindle_control.c
@@ -64,7 +64,6 @@ void spindle_init()
 
 uint8_t spindle_get_state()
 {
-  // TODO add INVERT_SPINDLE_PWM handling
   #ifdef VARIABLE_SPINDLE
     #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
       // No spindle direction output pin.