fix(threading): one hook switch to rule them all

config.env.example

@@ -32,6 +32,7 @@ ASSISTANT_NUMBER=5550000
 # ---------------------------------------------------------------------------
 
 HOOK_SWITCH_PIN=17
+SD_AMP_PIN=22                                                               
 PULSE_SWITCH_PIN=27
 
 # ---------------------------------------------------------------------------
@@ -40,7 +41,7 @@ PULSE_SWITCH_PIN=27
 
 # ALSA device name passed to aplay -D. Use "plughw:MAX98357A" for the
 # I2S amplifier or "default" to route through PipeWire/PulseAudio.
-ALSA_DEVICE=plughw:MAX98357A
+ALSA_DEVICE=plughw:2,0
 
 # Software volume multiplier (0.0–1.0). Lower if the amp clips or buzzes.
 # The MAX98357A with floating GAIN pin has 15 dB hardware gain, so 0.4 is

config.env.local

@@ -2,21 +2,6 @@
 # Copy to /etc/hello-operator/config.env and fill in values before starting.
 # Lines beginning with # are comments and are ignored.
 
-# ---------------------------------------------------------------------------
-# Plex (required)
-# ---------------------------------------------------------------------------
-
-# Full URL of your Plex Media Server
-PLEX_URL=http://localhost:32400
-
-# Plex authentication token
-# Find yours at: https://support.plex.tv/articles/204059436
-PLEX_TOKEN=
-
-# Machine identifier of the Plex player to control
-# Find yours in Plex Settings → Troubleshooting → "Download logs" or via the API
-PLEX_PLAYER_IDENTIFIER=
-
 # ---------------------------------------------------------------------------
 # Phone system (required)
 # ---------------------------------------------------------------------------

docs/AMP_SETUP.md

@@ -165,21 +165,16 @@ Power-cycle the board after changing the gain wiring.
 
 ## Channel selection (SD pin)
 
-For reference, the SD pin voltage ranges are:
-
-1. Wire MAX98357A **SD** to **GPIO 22** (physical pin 15) instead of Vin.
-2. Set `AMP_SD_PIN=22` in `/etc/hello-operator/config.env`.
+The breakout board's SD pin has a 1MΩ pull-up to Vin, which selects **stereo average** output `(L+R)/2` by default — appropriate for mono use with a stereo audio source.
 
-hello-operator handles the rest automatically at startup.
-
-### SD pin voltage reference
+For reference, the SD pin voltage ranges are:
 
-| SD pin voltage | Outage |
+| SD pin voltage | Output |
 |---|---|
-| < 0.16 V | Shutdown |
-| 0.16 V – 0.77 V | Stereo average (L+R)/2 |
-| 0.77 V – 1.4 V | Right channel only |
-| > 1.4 V | Left channel only |
+| < 0.16V | Amplifier shutdown |
+| 0.16V – 0.77V | Stereo average (L+R)/2 |
+| 0.77V – 1.4V | Right channel only |
+| > 1.4V | Left channel only |
 
 The SD pin is also used for instant audio cutoff — see Step 5 below.
 

install.sh

@@ -47,17 +47,17 @@ echo ""
 # System packages
 # ---------------------------------------------------------------------------
 
-echo "==> Installing system packages..."
-apt-get update -qq
-apt-get install -y \
-    python3 \
-    python3-venv \
-    python3-pip \
-    alsa-utils \
-    rtl-sdr \
-    mpd \
-    mpc \
-    mopidy
+# echo "==> Installing system packages..."
+# apt-get update -qq
+# apt-get install -y \
+#     python3 \
+#     python3-venv \
+#     python3-pip \
+#     alsa-utils \
+#     rtl-sdr \
+#     mpd \
+#     mpc \
+#     mopidy
 
 # ---------------------------------------------------------------------------
 # Config directory and files

src/audio.py

@@ -17,6 +17,7 @@
 """
 
 import io
+import logging
 import queue
 import subprocess
 import threading
@@ -26,6 +27,8 @@
 
 from src.interfaces import AudioInterface
 
+log = logging.getLogger(__name__)
+
 # Sample rate for the persistent aplay stream.  All audio is converted to
 # this rate before being written.
 _SAMPLE_RATE = 44100
@@ -97,7 +100,8 @@ class SounddeviceAudio(AudioInterface):
     """
 
     def __init__(self, sample_rate: int = _SAMPLE_RATE, device: str = "default",
-                 volume: float = 1.0, _popen=None) -> None:
+                 volume: float = 1.0, sd_pin: int = None,
+                 _popen=None, _gpio_output=None) -> None:
         self._sample_rate = sample_rate
         self._device = device
         self._volume = max(0.0, min(1.0, volume))
@@ -107,20 +111,37 @@ def __init__(self, sample_rate: int = _SAMPLE_RATE, device: str = "default",
         self._queue: queue.Queue = queue.Queue()
         self._busy = False
 
-        self._proc = self._popen(
-            ['aplay', '-q', '-D', self._device,
-             '-f', 'S16_LE', '-r', str(self._sample_rate), '-c', '1'],
-            stdin=subprocess.PIPE,
-            stdout=subprocess.DEVNULL,
-            stderr=subprocess.DEVNULL,
-        )
-
-        _warmup_frames = int(self._sample_rate * _WARMUP_MS / 1000)
-        _warmup_silence = np.zeros(_warmup_frames, dtype=np.int16).tobytes()
-        try:
-            self._proc.stdin.write(_warmup_silence)
-        except (BrokenPipeError, OSError):
-            pass
+        # SD pin: drive LOW to cut amp instantly; release to INPUT to re-enable.
+        # Both callables are None when sd_pin is not configured.
+        self._amp_off = None
+        self._amp_on = None
+        if sd_pin is not None:
+            if _gpio_output is not None:
+                self._amp_off = lambda: _gpio_output(sd_pin, False)
+                self._amp_on = lambda: _gpio_output(sd_pin, None)
+            else:
+                try:
+                    import RPi.GPIO as GPIO  # type: ignore[import]
+                    _pin = sd_pin
+                    GPIO.setmode(GPIO.BCM)
+                    GPIO.setup(_pin, GPIO.IN)
+
+                    def _amp_off(_p=_pin, _g=GPIO):
+                        log.info("SD pin %d → OUTPUT LOW (amp off)", _p)
+                        _g.setup(_p, _g.OUT)
+                        _g.output(_p, _g.LOW)
+
+                    def _amp_on(_p=_pin, _g=GPIO):
+                        log.debug("SD pin %d → INPUT (amp on)", _p)
+                        _g.setup(_p, _g.IN)
+
+                    self._amp_off = _amp_off
+                    self._amp_on = _amp_on
+                    log.info("SD amp pin configured: BCM %d", sd_pin)
+                except Exception as exc:
+                    log.warning("SD amp pin setup failed (pin %d): %s", sd_pin, exc)
+
+        self._proc = None
 
         self._worker_thread = threading.Thread(target=self._worker_loop, daemon=True)
         self._worker_thread.start()
@@ -157,6 +178,37 @@ def play_off_hook_tone(self) -> None:
         pcm = self._waveform_to_pcm(waveform)
         self._enqueue(lambda: self._write_pcm_loop(pcm))
 
+    def amp_off(self) -> None:
+        """Cut the amp and terminate aplay. Call only from the hook watcher."""
+        if self._amp_off:
+            self._amp_off()
+        self.stop()
+        proc, self._proc = self._proc, None
+        if proc is not None:
+            try:
+                proc.terminate()
+            except OSError:
+                pass
+
+    def amp_on(self) -> None:
+        """Start aplay and enable the amp. Call only from the hook watcher."""
+        if self._proc is None or self._proc.poll() is not None:
+            self._proc = self._popen(
+                ['aplay', '-q', '-D', self._device,
+                 '-f', 'S16_LE', '-r', str(self._sample_rate), '-c', '1'],
+                stdin=subprocess.PIPE,
+                stdout=subprocess.DEVNULL,
+                stderr=subprocess.DEVNULL,
+            )
+            _warmup_frames = int(self._sample_rate * _WARMUP_MS / 1000)
+            _warmup_silence = np.zeros(_warmup_frames, dtype=np.int16).tobytes()
+            try:
+                self._proc.stdin.write(_warmup_silence)
+            except (BrokenPipeError, OSError):
+                pass
+        if self._amp_on:
+            self._amp_on()
+
     def stop(self) -> None:
         """Stop current playback and clear all queued tasks.
 
@@ -209,9 +261,12 @@ def _worker_loop(self) -> None:
                     self._busy = False
 
     def _write_raw(self, pcm: bytes) -> None:
-        """Write raw PCM bytes to the persistent aplay stdin; swallow broken pipe."""
+        """Write raw PCM bytes to aplay stdin; no-op if aplay is not running."""
+        proc = self._proc
+        if proc is None:
+            return
         try:
-            self._proc.stdin.write(pcm)
+            proc.stdin.write(pcm)
         except (BrokenPipeError, OSError):
             pass
 

src/constants.py

@@ -20,7 +20,7 @@
 # Audio output device (ALSA device name passed to aplay -D)
 # ---------------------------------------------------------------------------
 
-ALSA_DEVICE = os.environ.get("ALSA_DEVICE", "plughw:MAX98357A")
+ALSA_DEVICE = os.environ.get("ALSA_DEVICE", "hw:2,0")
 
 # Software volume multiplier applied to all audio output (0.0–1.0).
 # Reduce if the amp clips or buzzes; increase if output is too quiet.
@@ -39,7 +39,7 @@
 # Timing constants (in seconds unless noted)
 # ---------------------------------------------------------------------------
 
-DIAL_TONE_TIMEOUT_IDLE = 5       # Silence before idle operator prompt
+DIAL_TONE_TIMEOUT_IDLE = 3       # Silence before idle operator prompt
 DIAL_TONE_TIMEOUT_PLAYING = 2    # Silence before playing-state prompt
 INTER_DIGIT_TIMEOUT = 0.3        # Gap after last pulse → digit complete (300 ms)
 DIRECT_DIAL_DISAMBIGUATION_TIMEOUT = 1.5  # TODO: tune on hardware — wait after first digit before treating as single nav input
@@ -84,6 +84,8 @@
 # GPIO pin assignments (BCM numbering) — optional; defaults match recommended wiring docs
 HOOK_SWITCH_PIN = int(os.environ.get("HOOK_SWITCH_PIN", "17"))
 PULSE_SWITCH_PIN = int(os.environ.get("PULSE_SWITCH_PIN", "27"))
+_sd_amp_pin_env = os.environ.get("SD_AMP_PIN")
+SD_AMP_PIN: int | None = int(_sd_amp_pin_env) if _sd_amp_pin_env is not None else None
 
 # Radio configuration
 RADIO_CONFIG_PATH = "/etc/hello-operator/radio_stations.json"