Add stepsToStop() for issue #274

CHANGELOG.md

@@ -9,6 +9,7 @@ TODO:
 pre-0.30.16:
 - Fix missing parenthesis in preprocessor macro (#271)
 - Position parameter for `forceStopAndNewPosition()` changed from `uint32_t` to `int32_t` (#268)
+- Add `stepsToStop()` to predict motor stop position
 
 0.30.15:
 - Fix missing initialization in `getCurrentSpeedInTicks()` (#262)

src/FastAccelStepper.h

@@ -517,6 +517,21 @@ class FastAccelStepper {
   void stopMove();
   inline bool isStopping() { return _rg.isStopping(); }
 
+  // ### stepsToStop()
+  // This returns the current step value of the ramp.
+  // This equals the number of steps for a motor to
+  // reach the current position and speed from standstill
+  // and to come to standstill with deceleration if stopped
+  // immediately.
+  // This value is valid with or without linear acceleration
+  // being used.
+  // Primary use is to forecast possible stop position.
+  // The stop position is:
+  //    getCurrentPosition() + stepsToStop()
+  // in case of a motor running in positive direction.
+  uint32_t stepsToStop() { return _rg.stepsToStop(); }
+
+
   // ### forceStop()
   // Abruptly stop the running stepper without deceleration.
   // This can be called from an interrupt !

src/RampGenerator.h

@@ -82,7 +82,12 @@ class RampGenerator {
     return _ro.isStopInitiated() && isRampGeneratorActive();
   }
   inline bool isRampGeneratorActive() { return rampState() != RAMP_STATE_IDLE; }
-
+  inline uint32_t stepsToStop() {
+    fasDisableInterrupts();
+    uint32_t v = _rw.performed_ramp_up_steps;
+    fasEnableInterrupts();
+    return v;
+  }
   inline void stopRamp() { _rw.stopRamp(); }
   inline void setKeepRunning() { _ro.setKeepRunning(); }
   inline bool isRunningContinuously() { return _ro.isRunningContinuously(); }