fix: active poll instead of wait for interupt

pi/README.md

@@ -162,7 +162,7 @@ The deployed service uses these environment variables:
 | Variable | Default | Description |
 |---|---|---|
 | `NOISEBELL_GPIO_PIN` | `17` | GPIO pin number |
-| `NOISEBELL_DEBOUNCE_SECS` | `5` | Debounce delay in seconds |
+| `NOISEBELL_DEBOUNCE_MS` | `50` | Debounce delay in milliseconds |
 | `NOISEBELL_PORT` | `80` | HTTP server port |
 | `NOISEBELL_ENDPOINT_URL` | required | Webhook URL to POST state changes to |
 | `NOISEBELL_RETRY_ATTEMPTS` | `3` | Webhook retry count |

pi/module.nix

@@ -14,10 +14,10 @@ in
       description = "GPIO pin number to monitor.";
     };
 
-    debounceSecs = lib.mkOption {
+    debounceMs = lib.mkOption {
       type = lib.types.ints.positive;
-      default = 5;
-      description = "Debounce delay in seconds.";
+      default = 50;
+      description = "Debounce delay in milliseconds.";
     };
 
     port = lib.mkOption {
@@ -88,12 +88,15 @@ in
     systemd.services.noisebell = {
       description = "Noisebell GPIO door monitor";
       wantedBy = [ "multi-user.target" ];
-      after = [ "network-online.target" "tailscaled.service" ];
+      after = [
+        "network-online.target"
+        "tailscaled.service"
+      ];
       wants = [ "network-online.target" ];
 
       environment = {
         NOISEBELL_GPIO_PIN = toString cfg.gpioPin;
-        NOISEBELL_DEBOUNCE_SECS = toString cfg.debounceSecs;
+        NOISEBELL_DEBOUNCE_MS = toString cfg.debounceMs;
         NOISEBELL_PORT = toString cfg.port;
         NOISEBELL_RETRY_ATTEMPTS = toString cfg.retryAttempts;
         NOISEBELL_RETRY_BASE_DELAY_SECS = toString cfg.retryBaseDelaySecs;

pi/pi-service/src/main.rs

@@ -7,7 +7,7 @@ use axum::extract::State;
 use axum::http::{HeaderMap, StatusCode};
 use axum::routing::get;
 use axum::{Json, Router};
-use gpiod::{Bias, Chip, Edge, EdgeDetect, Options};
+use gpiod::{Bias, Chip, Options};
 use noisebell_common::{
     validate_bearer, DoorStatus, PiStatusResponse, SignalLevel, WebhookPayload,
 };
@@ -88,10 +88,10 @@ async fn main() -> Result<()> {
         .parse()
         .context("NOISEBELL_GPIO_PIN must be a valid u32")?;
 
-    let debounce_secs: u64 = std::env::var("NOISEBELL_DEBOUNCE_SECS")
-        .unwrap_or_else(|_| "5".into())
+    let debounce_ms: u64 = std::env::var("NOISEBELL_DEBOUNCE_MS")
+        .unwrap_or_else(|_| "50".into())
         .parse()
-        .context("NOISEBELL_DEBOUNCE_SECS must be a valid u64")?;
+        .context("NOISEBELL_DEBOUNCE_MS must be a valid u64")?;
 
     let port: u16 = std::env::var("NOISEBELL_PORT")
         .unwrap_or_else(|_| "8080".into())
@@ -133,7 +133,7 @@ async fn main() -> Result<()> {
     let inbound_api_key = std::env::var("NOISEBELL_INBOUND_API_KEY")
         .context("NOISEBELL_INBOUND_API_KEY is required")?;
 
-    info!(gpio_pin, debounce_secs, port, %endpoint_url, "starting noisebell");
+    info!(gpio_pin, debounce_ms, port, %endpoint_url, "starting noisebell");
 
     let chip = Chip::new("gpiochip0").context("failed to open gpiochip0")?;
 
@@ -143,12 +143,13 @@ async fn main() -> Result<()> {
         Bias::PullDown
     };
 
-    // Request the line with edge detection for monitoring
+    // Keep the line requested and poll its value. Edge-triggered reads have
+    // proven unreliable on Raspberry Pi OS even though the raw line level is
+    // correct, so we debounce from sampled levels instead.
     let opts = Options::input([gpio_pin])
         .bias(bias)
-        .edge(EdgeDetect::Both)
         .consumer("noisebell");
-    let mut inputs = chip
+    let inputs = chip
         .request_lines(opts)
         .context(format!("failed to request GPIO line {gpio_pin}"))?;
 
@@ -183,47 +184,58 @@ async fn main() -> Result<()> {
     // Sync initial state with the cache on startup
     let _ = tx.send((initial_state.as_door_status(), now));
 
-    // Spawn blocking edge detection task. The async tokio-gpiod path was
-    // returning repeated EAGAIN on Raspberry Pi OS even when no real GPIO
-    // error occurred.
+    // Poll the input level and debounce in software. This is less elegant than
+    // edge-triggered reads, but it is robust on Raspberry Pi OS.
     let state_for_edges = state.clone();
     let edge_tx = tx.clone();
     let _edge_handle = std::thread::spawn(move || {
-        let mut last_event_time = std::time::Instant::now() - Duration::from_secs(debounce_secs);
-        let debounce = Duration::from_secs(debounce_secs);
+        let poll_interval = Duration::from_millis(25);
+        let debounce = Duration::from_millis(debounce_ms);
+        let mut current_state = initial_state;
+        let mut pending_state = current_state;
+        let mut pending_since = std::time::Instant::now();
 
         loop {
-            let event = match inputs.read_event() {
-                Ok(event) => event,
-                Err(e) if e.kind() == std::io::ErrorKind::Interrupted => continue,
+            let values = match inputs.get_values([false]) {
+                Ok(values) => values,
                 Err(e) => {
-                    error!(error = %e, "failed to read GPIO event");
+                    error!(error = %e, "failed to read GPIO value");
                     std::thread::sleep(Duration::from_secs(1));
                     continue;
                 }
             };
 
-            // Software debounce
-            if last_event_time.elapsed() < debounce {
-                continue;
-            }
-            last_event_time = std::time::Instant::now();
-
-            let new_raw_level = match event.edge {
-                Edge::Falling => SignalLevel::Low,
-                Edge::Rising => SignalLevel::High,
+            let new_raw_level = if values[0] {
+                SignalLevel::High
+            } else {
+                SignalLevel::Low
             };
             let new_state = LocalDoorState::from_raw_level(new_raw_level, active_level);
 
-            let previous_state =
-                LocalDoorState::from_atomic(state_for_edges.door_state.swap(new_state as u8, Ordering::Relaxed));
-            if previous_state != new_state {
+            if new_state != pending_state {
+                pending_state = new_state;
+                pending_since = std::time::Instant::now();
+            } else if new_state != current_state && pending_since.elapsed() >= debounce {
+                current_state = new_state;
+                let previous_state = LocalDoorState::from_atomic(
+                    state_for_edges
+                        .door_state
+                        .swap(new_state as u8, Ordering::Relaxed),
+                );
+
+                if previous_state == new_state {
+                    std::thread::sleep(poll_interval);
+                    continue;
+                }
+
                 let timestamp = unix_timestamp();
                 state_for_edges
                     .last_changed
                     .store(timestamp, Ordering::Relaxed);
                 let _ = edge_tx.send((new_state.as_door_status(), timestamp));
             }
+
+            std::thread::sleep(poll_interval);
         }
     });
     drop(tx); // Drop original sender so rx closes when edge_handle is dropped

scripts/deploy-pios-pi.sh

@@ -84,7 +84,7 @@ sudo chmod 600 /etc/noisebell/pi-to-cache-key /etc/noisebell/cache-to-pi-key /et
 
 sudo tee /etc/noisebell/noisebell.env >/dev/null <<'ENVEOF'
 NOISEBELL_GPIO_PIN=17
-NOISEBELL_DEBOUNCE_SECS=5
+NOISEBELL_DEBOUNCE_MS=50
 NOISEBELL_PORT=80
 NOISEBELL_RETRY_ATTEMPTS=3
 NOISEBELL_RETRY_BASE_DELAY_SECS=1