stepper: Reset the next step time on a stepper stop

Automatically reset the next step time to zero on a stepper_stop()
call.  This makes the host code simpler as it no longer needs to
schedule an explicit reset_step_clock command on the step after a
homing operation.

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

klippy/mcu.py

@@ -22,7 +22,6 @@ class MCU_stepper:
         self._oid = mcu.create_oid()
         step_pin, pullup, invert_step = parse_pin_extras(step_pin)
         dir_pin, pullup, self._invert_dir = parse_pin_extras(dir_pin)
-        self._need_reset = True
         self._mcu_freq = mcu.get_mcu_freq()
         min_stop_interval = int(min_stop_interval * self._mcu_freq)
         max_error = int(max_error * self._mcu_freq)
@@ -47,11 +46,8 @@ class MCU_stepper:
     def get_invert_dir(self):
         return self._invert_dir
     def note_stepper_stop(self):
-        self._need_reset = True
-    def check_reset(self, mcu_time):
-        if not self._need_reset:
-            return
-        self._need_reset = False
+        self.ffi_lib.stepcompress_reset(self._stepqueue, 0)
+    def reset_step_clock(self, mcu_time):
         clock = int(mcu_time * self._mcu_freq)
         self.ffi_lib.stepcompress_reset(self._stepqueue, clock)
         data = (self._reset_cmd.msgid, self._oid, clock & 0xffffffff)
@@ -486,7 +482,7 @@ class Dummy_MCU_stepper:
             self._stepid, dirstr, countstr, addstr, interval))
     def set_next_step_dir(self, dir):
         self._sdir = dir
-    def check_reset(self, clock):
+    def reset_step_clock(self, clock):
         self._mcu.outfile.write("G6S%dT%d\n" % (self._stepid, clock))
     def print_to_mcu_time(self, print_time):
         return self._mcu.print_to_mcu_time(print_time)

klippy/stepper.py

@@ -71,8 +71,8 @@ class PrinterStepper:
         self.need_motor_enable = True
     def prep_move(self, move_time):
         mcu_time = self.mcu_stepper.print_to_mcu_time(move_time)
-        self.mcu_stepper.check_reset(mcu_time)
         if self.need_motor_enable:
+            self.mcu_stepper.reset_step_clock(mcu_time)
             self.motor_enable(move_time, 1)
             self.need_motor_enable = False
         return (mcu_time, self.mcu_stepper)

src/stepper.c

@@ -238,6 +238,7 @@ void
 stepper_stop(struct stepper *s)
 {
     sched_del_timer(&s->time);
+    s->next_step_time = 0;
     s->position = -stepper_get_position(s);
     s->count = 0;
     s->flags &= SF_INVERT_STEP;