fixed steppers not stopping from setSpeed(0) (#208)

* fixed steppers not stopping from setSpeed(0)

* version bump and changelog

* replaced float equality comparison with "less than"

* removed custom ABS definition in favor of arduino abs

* using type specific fabsf instead of generic abs

Author: andre-stefanov

Changelog.md

@@ -1,3 +1,6 @@
+**V1.12.2 - Updates**
+- Fixed a bug that caused Focuser stepper to misbehave after booting.
+
 **V1.12.1 - Updates**
 - Fixed a bug that caused Autohoming to cause a build break.
 - Fixed a bug that would prevent Hall sensor based Autohoming from completing.

Version.h

@@ -3,4 +3,4 @@
 // Also, numbers are interpreted as simple numbers.                        _   __   _
 // So 1.8 is actually 1.08, meaning that 1.12 is a later version than 1.8.  \_(..)_/
 
-#define VERSION "V1.12.1"
+#define VERSION "V1.12.2"

src/InterruptAccelStepper.h

@@ -8,10 +8,11 @@
 #include <stdint.h>
 #include <math.h>
 
-#define ABS(x) ((x >= 0) ? x : -x)
-
 #define SIGN(x) ((x >= 0) ? 1 : -1)
 
+// minimal stepping frequency (steps/s) based on cpu frequency, timer counter overflow and max amount of overflows
+#define MIN_STEPS_PER_SEC (static_cast<float>(F_CPU) / (UINT16_MAX * UINT8_MAX))
+
 template <typename STEPPER> class InterruptAccelStepper
 {
   private:
@@ -47,7 +48,7 @@ template <typename STEPPER> class InterruptAccelStepper
     void setMaxSpeed(float speed)
     {
         LOG(DEBUG_STEPPERS, "[IAS-%d] setMaxSpeed(%f)", STEPPER::TIMER_ID, speed);
-        _max_speed = ABS(speed);
+        _max_speed = fabsf(speed);
     }
 
     void setAcceleration(float value)
@@ -64,7 +65,15 @@ template <typename STEPPER> class InterruptAccelStepper
     {
         LOG(DEBUG_STEPPERS, "[IAS-%d] setSpeed(%f)", STEPPER::TIMER_ID, speed);
         _speed = speed;
-        STEPPER::moveTo(_speed, INT32_MAX);
+
+        if (fabsf(speed) < MIN_STEPS_PER_SEC)
+        {
+            STEPPER::stop();
+        }
+        else
+        {
+            STEPPER::moveTo(_speed, INT32_MAX);
+        }
     }
 
     float speed()