Fix dance-loop tremor (set_target) and raspotify restart lockup (#1130)

spotify_dancer/main.py

@@ -432,6 +432,23 @@ def check_and_fix_alsa_config():
     logger.info(f"Detected: speaker=card {speaker_card}, loopback=card {loopback_card}")
 
     config = generate_alsa_config(speaker_card, loopback_card)
+
+    # Idempotency guard: only rewrite /etc/asound.conf and restart raspotify when
+    # the config actually changes. Restarting raspotify while the audio analyzer
+    # holds the ALSA loopback capture (loopback_in) wedges ALSA in an EINVAL state
+    # ("Slave PCM not usable") that survives until a reboot. The aplay probe above
+    # can fail transiently for that exact reason while the on-disk config is
+    # already correct, so a byte-identical config must not trigger a restart.
+    try:
+        with open('/etc/asound.conf', 'r') as f:
+            existing_config = f.read()
+    except OSError:
+        existing_config = None
+
+    if existing_config == config:
+        logger.info("ALSA config already up to date, skipping rewrite and restart")
+        return True
+
     try:
         with open('/tmp/asound.conf', 'w') as f:
             f.write(config)
@@ -499,6 +516,12 @@ class SpotifyDancer(ReachyMiniApp):
                 self.latest_features = self.analyzer.latest_features
                 movement = self.controller.update(self.latest_features, dt)
 
+                # Deadzone: when there is effectively no audio, hold a neutral
+                # pose instead of reacting to numeric noise. Without this the
+                # robot twitches continuously even when nothing is playing.
+                if self.latest_features.rms < 0.02:
+                    movement = {key: 0.0 for key in movement}
+
                 try:
                     head_pose = create_head_pose(
                         z=movement['head_z'],
@@ -506,12 +529,17 @@ class SpotifyDancer(ReachyMiniApp):
                         mm=True,
                         degrees=True
                     )
-                    reachy_mini.goto_target(
+                    # Use set_target (not goto_target) inside this ~20 Hz control
+                    # loop. goto_target starts a fresh min-jerk profile from zero
+                    # velocity on every call and blocks until it completes; calling
+                    # it every 50 ms makes the profile restart 20x/s, producing
+                    # visible head/antenna tremor independent of the music.
+                    # AGENTS.md: set_target for loops >=10 Hz, goto_target only for
+                    # one-shot gestures >=0.5 s.
+                    reachy_mini.set_target(
                         head=head_pose,
                         antennas=[movement['antenna_left'], movement['antenna_right']],
                         body_yaw=np.deg2rad(movement['body_yaw']),
-                        duration=0.1,
-                        method="minjerk"
                     )
                 except Exception as e:
                     logger.debug(f"Movement error: {e}")