Switch the motors off when the designs are done or stopped

After the last design (or a Stop), the player sends $SLP (GRBL and FluidNC
sleep), so the motors stop holding and the table is quiet. The page shows
"Motors off"; the next design wakes the controller (reset + unlock) and homes
first, since the arm can be moved by hand while the motors are off. The jog
panel wakes it too. Setting: motion.motors_off_when_done (default true).

Checked on the real Uno: Idle -> $SLP -> Sleep -> reset -> Alarm -> $X -> Idle.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

software/sandtable/cli.py

@@ -353,6 +353,18 @@ def cmd_play(cfg, args):
 
 
 def _play(c, cfg, args, items):
+    try:
+        _play_list(c, cfg, args, items)
+    finally:
+        if cfg['motion'].get('motors_off_when_done', True):
+            try:
+                c.motors_off()                  # done, stopped or failed: let the motors rest
+                print('  motors off')
+            except Exception:
+                pass                            # e.g. the USB link has gone
+
+
+def _play_list(c, cfg, args, items):
     if not args.no_home:
         print('  homing rho ...', flush=True)
         c.home_rho(cfg)

software/sandtable/config.py

@@ -26,6 +26,8 @@ DEFAULTS = {
     },
     'motion': {
         'ball_speed_mm_s': 25.0,   # drawing speed of the ball across the sand
+        'motors_off_when_done': True,   # switch the motors off when the designs are done or stopped
+                                        # (quiet, cool); the next design homes first
         'max_theta_deg_s': 60.0,   # arm spin limit (10 rpm)
         'max_rho_mm_s': 25.0,      # carriage limit
         'theta_accel_deg_s2': 120.0,

software/sandtable/grbl.py

@@ -346,7 +346,33 @@ class Controller:
             self._presses = 0
         return self.query()
 
+    def motors_off(self):
+        """Switch the motors off with the sleep command ($SLP; FluidNC has it too). They stop
+        holding, so the arm turns by hand and the position is lost: before moving again the
+        controller needs waking (a reset, see wake_up) and the table homing."""
+        self.guard = None
+        if self.query().state != 'Sleep':
+            self.command('$SLP')
+        self.query()
+
+    def wake_up(self):
+        """Out of sleep: only a reset wakes it, and it then waits in ALARM until unlocked."""
+        if self.query().state != 'Sleep':
+            return
+        self.realtime(RT_RESET)
+        t_end, seen = time.monotonic() + 3, None
+        while time.monotonic() < t_end:
+            for line in self._lines():
+                if 'grbl' in line.lower() or 'fluidnc' in line.lower():
+                    seen = time.monotonic()
+            if seen and time.monotonic() - seen > 0.2:
+                break
+            time.sleep(0.02)
+        self.pending.clear()
+        self.query()
+
     def unlock(self):
+        self.wake_up()
         if self.query().state == 'Alarm':
             self.command('$X')
 

software/sandtable/ui.py

@@ -212,7 +212,8 @@ class Panel:
 
     def status(self):
         st = self.c.status
-        return {'state': 'Disconnected' if not self.connected else self.busy or (st.state + (':' + st.sub if st.sub else '')),
+        state = 'Motors off' if st.state == 'Sleep' else st.state + (':' + st.sub if st.sub else '')
+        return {'state': 'Disconnected' if not self.connected else self.busy or state,
                 'connected': self.connected,
                 'theta': st.wpos[0], 'rho': st.wpos[1], 'switch': 'Y' in st.pins, 'pins': st.pins,
                 'homed': self.homed, 'steps': self.steps, 'error': self.error}
@@ -224,6 +225,9 @@ class Panel:
         feed = 1200 if axis == 'X' else 600       # 20 deg/s, 10 mm/s
         with self.lock:
             st = self.c.query()
+            if st.state == 'Sleep':                 # motors switched off after a design: wake them
+                self.c.unlock()
+                st = self.c.query()
             if st.state == 'Alarm':
                 return False, 'alarm: press Unlock first'
             inward = axis == 'Y' and d < 0
@@ -263,6 +267,7 @@ class Panel:
 
     def unlock(self):
         with self.lock:
+            self.c.unlock()                         # also wakes the motors after a design
             self.c.command('$X')
         return True, 'unlocked'
 

software/sandtable/web.py

@@ -275,6 +275,13 @@ class Player:
             finally:
                 c.guard = None
                 c.abort = False
+                if self.cfg['motion'].get('motors_off_when_done', True) and self.p.connected:
+                    try:
+                        c.motors_off()              # done or stopped: let the motors rest
+                        self.p.homed = False        # the arm can drift now, so home before the next one
+                        log('motors off')
+                    except Exception as e:
+                        log(f'could not switch the motors off: {e!r}')
                 self.now = None
                 self.state = 'idle'