stepper: Support configuring the stepper pulse length from Kconfig

Allow the stepper pulse length to be configured at compile time from
the Kconfig menu system.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

3 files changed, 41 insertions, 15 deletions

diff --git a/src/Kconfig b/src/Kconfig
index e94ff5b2..16ce3531 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -2,6 +2,13 @@
 
 mainmenu "Klipper Firmware Configuration"
 
+config LOW_LEVEL_OPTIONS
+    bool "Enable extra low-level configuration options"
+    default n
+    help
+        Enable low-level configuration options that (if modified) may
+        result in a build that does not function correctly.
+
 choice
     prompt "Micro-controller Architecture"
     config MACH_AVR
@@ -32,6 +39,29 @@ source "src/linux/Kconfig"
 source "src/simulator/Kconfig"
 
 
+# Step timing customization
+config CUSTOM_STEP_DELAY
+    bool "Specify a custom step pulse duration"
+    depends on LOW_LEVEL_OPTIONS
+config STEP_DELAY
+    int
+    default 2
+config STEP_DELAY
+    int "Step pulse duration (in microseconds)"
+    depends on CUSTOM_STEP_DELAY
+    help
+        Specify the duration of the stepper step pulse time. This
+        setting applies to all stepper drivers controlled by the
+        micro-controller. If this value is set to zero then the code
+        will "step" and "unstep" in the same C function.
+
+        The default is zero for 8-bit AVR based micro-controllers, as
+        it takes a little over 2us to step and unstep with this
+        setting.
+
+        The default for all other micro-controllers is 2us.
+
+        CUSTOMIZING THIS VALUE DOES NOT IMPROVE PERFORMANCE!
 
 # The HAVE_GPIO_x options allow boards to disable support for some
 # commands if the hardware does not support the feature.
@@ -54,13 +84,6 @@ config HAVE_GPIO_BITBANGING
     bool
     default n
 
-config NO_UNSTEP_DELAY
-    # Slow micro-controllers do not require a delay before returning a
-    # stepper step pin to its default level.  A board can enable this
-    # option to optimize the stepper_event() handler in this case.
-    bool
-    default n
-
 config INLINE_STEPPER_HACK
     # Enables gcc to inline stepper_event() into the main timer irq handler
     bool
diff --git a/src/avr/Kconfig b/src/avr/Kconfig
index b2d6ffe0..2a1ca0b8 100644
--- a/src/avr/Kconfig
+++ b/src/avr/Kconfig
@@ -11,7 +11,9 @@ config AVR_SELECT
     select HAVE_GPIO_I2C
     select HAVE_GPIO_HARD_PWM
     select HAVE_GPIO_BITBANGING if !MACH_atmega168
-    select NO_UNSTEP_DELAY
+
+config STEP_DELAY
+    default 0
 
 config BOARD_DIRECTORY
     string
diff --git a/src/stepper.c b/src/stepper.c
index 2b967413..8356ff24 100644
--- a/src/stepper.c
+++ b/src/stepper.c
@@ -13,6 +13,8 @@
 #include "sched.h" // struct timer
 #include "stepper.h" // command_config_stepper
 
+DECL_CONSTANT(STEP_DELAY, CONFIG_STEP_DELAY);
+
 
 /****************************************************************
  * Steppers
@@ -32,7 +34,7 @@ struct stepper {
     struct timer time;
     uint32_t interval;
     int16_t add;
-#if CONFIG_NO_UNSTEP_DELAY
+#if !CONFIG_STEP_DELAY
     uint16_t count;
 #define next_step_time time.waketime
 #else
@@ -68,7 +70,7 @@ stepper_load_next(struct stepper *s, uint32_t min_next_time)
     s->next_step_time += m->interval;
     s->add = m->add;
     s->interval = m->interval + m->add;
-    if (CONFIG_NO_UNSTEP_DELAY) {
+    if (!CONFIG_STEP_DELAY) {
         // On slow mcus see if the add can be optimized away
         s->flags = m->add ? s->flags | SF_HAVE_ADD : s->flags & ~SF_HAVE_ADD;
         s->count = m->count;
@@ -98,14 +100,12 @@ stepper_load_next(struct stepper *s, uint32_t min_next_time)
     return SF_RESCHEDULE;
 }
 
-#define UNSTEP_TIME timer_from_us(2)
-
 // Timer callback - step the given stepper.
 uint_fast8_t
 stepper_event(struct timer *t)
 {
     struct stepper *s = container_of(t, struct stepper, time);
-    if (CONFIG_NO_UNSTEP_DELAY) {
+    if (!CONFIG_STEP_DELAY) {
         // On slower mcus it is possible to simply step and unstep in
         // the same timer event.
         gpio_out_toggle_noirq(s->step_pin);
@@ -124,7 +124,8 @@ stepper_event(struct timer *t)
     }
 
     // On faster mcus, it is necessary to schedule the unstep event
-    uint32_t min_next_time = timer_read_time() + UNSTEP_TIME;
+    uint32_t step_delay = timer_from_us(CONFIG_STEP_DELAY);
+    uint32_t min_next_time = timer_read_time() + step_delay;
     gpio_out_toggle_noirq(s->step_pin);
     s->count--;
     if (likely(s->count & 1))
@@ -242,7 +243,7 @@ static uint32_t
 stepper_get_position(struct stepper *s)
 {
     uint32_t position = s->position;
-    if (CONFIG_NO_UNSTEP_DELAY)
+    if (!CONFIG_STEP_DELAY)
         position -= s->count;
     else
         position -= s->count / 2;