Detect a disconnected board via heartbeat (stop falsely showing "Broadcasting")

The dashboard trusted the last status token forever, so unplugging the ESP left
it claiming "Broadcasting". Add a liveness link:

- Firmware: emit a "PING" beacon ~every 2s from loop().
- Flipper: stamp last_rx_tick on any RX (PING or event); a 1s ViewDispatcher tick
  flags link_lost when nothing has arrived for FLYTRAP_LINK_TIMEOUT_MS (5s). The
  dashboard then shows "Board disconnected" (hollow indicator) instead of
  "Broadcasting", and recovers automatically when the board returns (its reboot
  re-runs the handshake). PING is kept out of the console so it doesn't spam it.

Note: both halves must be updated together — the new app expects the beacon, so
an old firmware without PING would read as a lost link when idle.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: tarikbc

esp32/flytrap-fw/flytrap-fw.ino

@@ -11,6 +11,7 @@
 //   BYE mac=<mac>    (a station left the AP)
 //   IP mac=<mac> ip=<ip>   (DHCP assigned a station its IP)
 //   CRED <urlencoded>   (all submitted form fields, one line per submission)
+//   PING             (~every 2s liveness beacon so the Flipper detects unplug)
 //
 // Authorized testing only.
 
@@ -252,4 +253,14 @@ void setup() {
 void loop() {
     if(portalRunning) dnsServer.processNextRequest();
     pumpSerial();
+
+    // Heartbeat: a periodic liveness beacon so the Flipper can tell the board is
+    // still attached (it shows "Broadcasting" until told otherwise). If the board
+    // is unplugged, these stop and the Flipper flags the link as lost.
+    static uint32_t lastPing = 0;
+    uint32_t now = millis();
+    if(now - lastPing >= 2000) {
+        lastPing = now;
+        emitLine("PING");
+    }
 }

flipper/flytrap/flytrap.c

@@ -24,6 +24,19 @@ static bool flytrap_back_event_callback(void* context) {
     return scene_manager_handle_back_event(app->scene_manager);
 }
 
+// Periodic tick: with no RX to wake us, this is how we notice the board went
+// away. If we haven't heard a PING (or any event) within the timeout, flag the
+// link as lost and redraw so the dashboard stops claiming "Broadcasting".
+static void flytrap_tick_callback(void* context) {
+    FlytrapApp* app = context;
+    if(!app->session_active) return;
+    bool stale = (furi_get_tick() - app->last_rx_tick) > FLYTRAP_LINK_TIMEOUT_MS;
+    if(stale && !app->link_lost) {
+        app->link_lost = true;
+        scene_manager_handle_custom_event(app->scene_manager, FlytrapEventRefreshView);
+    }
+}
+
 // Runs on the UART worker thread: just wake the GUI to drain/parse RX bytes.
 // The context is fixed for the app's lifetime, so this never races a toggle.
 static void flytrap_uart_notify(void* ctx) {
@@ -48,6 +61,7 @@ static FlytrapApp* flytrap_app_alloc(void) {
     view_dispatcher_set_event_callback_context(app->view_dispatcher, app);
     view_dispatcher_set_custom_event_callback(app->view_dispatcher, flytrap_custom_event_callback);
     view_dispatcher_set_navigation_event_callback(app->view_dispatcher, flytrap_back_event_callback);
+    view_dispatcher_set_tick_event_callback(app->view_dispatcher, flytrap_tick_callback, 1000);
     view_dispatcher_attach_to_gui(app->view_dispatcher, app->gui, ViewDispatcherTypeFullscreen);
 
     app->submenu = submenu_alloc();

flipper/flytrap/flytrap_i.h

@@ -25,6 +25,7 @@
 #define FLYTRAP_CLIENT_SLOTS (16)
 #define FLYTRAP_CAP_KV_SIZE (160)
 #define FLYTRAP_LINE_MAX (512)
+#define FLYTRAP_LINK_TIMEOUT_MS (5000) // no PING/data for this long -> board unplugged
 #define FLYTRAP_SESSION_BUF_MAX (4096) // scrollable captures/raw buffers
 
 #define FLYTRAP_DATA_DIR EXT_PATH("apps_data/flytrap")
@@ -100,6 +101,11 @@ typedef struct FlytrapApp {
 
     FlytrapTextViewMode textview_mode;
 
+    // Board liveness: the ESP beacons "PING" ~every 2s; if we hear nothing for
+    // FLYTRAP_LINK_TIMEOUT_MS the board is likely unplugged and we flag the link.
+    uint32_t last_rx_tick;
+    bool link_lost;
+
     // Handshake / lifecycle flags
     bool portal_running;
     bool pending_setap;

flipper/flytrap/helpers/flytrap_session.c

@@ -116,6 +116,10 @@ static void append_raw(FlytrapApp* app, const char* line) {
 }
 
 static void process_line(FlytrapApp* app, const char* line) {
+    // Liveness beacon: consumed for the freshness timer (handled by the caller
+    // updating last_rx_tick); kept out of the console so it doesn't spam it.
+    if(strcmp(line, "PING") == 0) return;
+
     append_raw(app, line); // everything is visible in the raw console
 
     if(strncmp(line, "STATUS ", 7) == 0) {
@@ -228,6 +232,8 @@ void flytrap_session_start(FlytrapApp* app) {
     app->client_count = 0;
     app->clients_rev = 0;
     app->selected_client = 0;
+    app->last_rx_tick = furi_get_tick();
+    app->link_lost = false;
     app->portal_running = false;
     app->pending_setap = false;
     app->need_restart = false;
@@ -258,8 +264,15 @@ void flytrap_session_stop(FlytrapApp* app) {
 void flytrap_session_rx(FlytrapApp* app) {
     uint8_t buf[128];
     size_t n;
+    bool got = false;
     while((n = flytrap_uart_rx(app->uart, buf, sizeof(buf))) > 0) {
         feed(app, buf, n);
+        got = true;
+    }
+    if(got) {
+        // Any traffic (PING or event) means the board is alive.
+        app->last_rx_tick = furi_get_tick();
+        app->link_lost = false;
     }
     if(app->need_restart) {
         // ESP rebooted mid-session; redo the handshake (keep buffers). Only clear

flipper/flytrap/scenes/flytrap_scene_live.c

@@ -41,8 +41,15 @@ static void flytrap_dash_refresh(FlytrapApp* app) {
         app->widget, 0, 18, AlignLeft, AlignTop, FontSecondary, furi_string_get_cstr(tmp));
 
     // Status: a filled dot when broadcasting (ring otherwise) + a polished label.
+    // A lost board link overrides whatever the last status token said.
     bool live = false;
-    const char* state = flytrap_state_label(furi_string_get_cstr(app->status), &live);
+    const char* state;
+    if(app->link_lost) {
+        state = "Board disconnected";
+        live = false;
+    } else {
+        state = flytrap_state_label(furi_string_get_cstr(app->status), &live);
+    }
     widget_add_circle_element(app->widget, 4, 31, 3, live);
     widget_add_string_element(app->widget, 12, 28, AlignLeft, AlignTop, FontSecondary, state);
 
@@ -83,7 +90,7 @@ static void flytrap_live_render(FlytrapApp* app) {
     bool live = false;
     flytrap_state_label(furi_string_get_cstr(app->status), &live);
     bool err = strstr(furi_string_get_cstr(app->status), "err") != NULL;
-    if(live || err) {
+    if(live || err || app->link_lost) {
         flytrap_dash_refresh(app);
     } else {
         flytrap_loading_render(app);