Forward rtl_fm stderr to Morse frontend diagnostic log

rtl_fm prints device info, tuning, and errors to stderr but the morse
route only logged these server-side. Now stderr lines are forwarded to
the morse queue as info events, displayed in a compact diagnostic log
below the scope canvas. After 10s with no audio data, the scope text
escalates to prompt the user to check the SDR log.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

routes/morse.py

@@ -158,12 +158,17 @@ def start_morse() -> Response:
                     morse_active_device = None
                 return jsonify({'status': 'error', 'message': msg}), 500
 
-            # Monitor rtl_fm stderr
+            # Forward rtl_fm stderr to queue so frontend can display diagnostics
             def monitor_stderr():
                 for line in rtl_process.stderr:
                     err_text = line.decode('utf-8', errors='replace').strip()
                     if err_text:
                         logger.debug(f"[rtl_fm/morse] {err_text}")
+                        with contextlib.suppress(queue.Full):
+                            app_module.morse_queue.put_nowait({
+                                'type': 'info',
+                                'text': f'[rtl_fm] {err_text}',
+                            })
 
             stderr_thread = threading.Thread(target=monitor_stderr)
             stderr_thread.daemon = True
@@ -190,6 +195,11 @@ def start_morse() -> Response:
             app_module.morse_process._decoder_thread = decoder_thread
 
             app_module.morse_queue.put({'type': 'status', 'status': 'started'})
+            with contextlib.suppress(queue.Full):
+                app_module.morse_queue.put_nowait({
+                    'type': 'info',
+                    'text': f'[cmd] {full_cmd}',
+                })
 
             return jsonify({
                 'status': 'started',

static/js/modes/morse.js

@@ -23,6 +23,7 @@ var MorseMode = (function () {
     var scopeThreshold = 0;
     var scopeToneOn = false;
     var scopeWaiting = false;
+    var waitingStart = 0;  // timestamp when waiting began
 
     // ---- Initialization ----
 
@@ -152,9 +153,13 @@ var MorseMode = (function () {
             // Update scope data
             var amps = msg.amplitudes || [];
             if (msg.waiting && amps.length === 0 && scopeHistory.length === 0) {
-                scopeWaiting = true;
+                if (!scopeWaiting) {
+                    scopeWaiting = true;
+                    waitingStart = Date.now();
+                }
             } else if (amps.length > 0) {
                 scopeWaiting = false;
+                waitingStart = 0;
             }
             for (var i = 0; i < amps.length; i++) {
                 scopeHistory.push(amps[i]);
@@ -178,6 +183,9 @@ var MorseMode = (function () {
                 disconnectSSE();
                 stopScope();
             }
+        } else if (type === 'info') {
+            appendDiagLine(msg.text);
+
         } else if (type === 'error') {
             console.error('Morse error:', msg.text);
         }
@@ -263,10 +271,14 @@ var MorseMode = (function () {
 
             if (scopeHistory.length === 0) {
                 if (scopeWaiting) {
-                    scopeCtx.fillStyle = '#556677';
+                    var elapsed = waitingStart ? (Date.now() - waitingStart) / 1000 : 0;
+                    var waitText = elapsed > 10
+                        ? 'No audio data \u2014 check SDR log below'
+                        : 'Awaiting SDR data\u2026';
+                    scopeCtx.fillStyle = elapsed > 10 ? '#887744' : '#556677';
                     scopeCtx.font = '12px monospace';
                     scopeCtx.textAlign = 'center';
-                    scopeCtx.fillText('Awaiting SDR data\u2026', w / 2, h / 2);
+                    scopeCtx.fillText(waitText, w / 2, h / 2);
                     scopeCtx.textAlign = 'start';
                 }
                 scopeAnim = requestAnimationFrame(draw);
@@ -371,6 +383,30 @@ var MorseMode = (function () {
         URL.revokeObjectURL(url);
     }
 
+    // ---- Diagnostic log ----
+
+    function appendDiagLine(text) {
+        var log = document.getElementById('morseDiagLog');
+        if (!log) return;
+        log.style.display = 'block';
+        var line = document.createElement('div');
+        line.textContent = text;
+        log.appendChild(line);
+        // Limit to 20 entries
+        while (log.children.length > 20) {
+            log.removeChild(log.firstChild);
+        }
+        log.scrollTop = log.scrollHeight;
+    }
+
+    function clearDiagLog() {
+        var log = document.getElementById('morseDiagLog');
+        if (log) {
+            log.innerHTML = '';
+            log.style.display = 'none';
+        }
+    }
+
     // ---- UI ----
 
     function updateUI(running) {
@@ -398,6 +434,14 @@ var MorseMode = (function () {
         var scopeStatus = document.getElementById('morseScopeStatusLabel');
         if (scopeStatus) scopeStatus.textContent = running ? 'ACTIVE' : 'IDLE';
         if (scopeStatus) scopeStatus.style.color = running ? '#0f0' : '#444';
+
+        // Diagnostic log: clear on start, hide on stop
+        if (running) {
+            clearDiagLog();
+        } else {
+            var diagLog = document.getElementById('morseDiagLog');
+            if (diagLog) diagLog.style.display = 'none';
+        }
     }
 
     function setFreq(mhz) {

templates/index.html

@@ -3085,6 +3085,11 @@
                     </div>
                 </div>
 
+                <div id="morseDiagLog" style="display: none; margin-bottom: 8px; max-height: 60px; overflow-y: auto;
+                    background: #080812; border: 1px solid #1a1a2e; border-radius: 4px; padding: 4px 8px;
+                    font-family: var(--font-mono); font-size: 10px; color: #556677; line-height: 1.6;">
+                </div>
+
                 <!-- Morse Decoded Output -->
                 <div id="morseOutputPanel" style="display: none; margin-bottom: 12px;">
                     <div style="background: #0a0a0a; border: 1px solid #1a2e1a; border-radius: 6px; padding: 8px 10px;">
@@ -4172,6 +4177,8 @@
             const morseOutputPanel = document.getElementById('morseOutputPanel');
             if (morseScopePanel && mode !== 'morse') morseScopePanel.style.display = 'none';
             if (morseOutputPanel && mode !== 'morse') morseOutputPanel.style.display = 'none';
+            const morseDiagLog = document.getElementById('morseDiagLog');
+            if (morseDiagLog && mode !== 'morse') morseDiagLog.style.display = 'none';
 
             // Update output panel title based on mode
             const outputTitle = document.getElementById('outputTitle');

utils/morse.py

@@ -278,6 +278,7 @@ def morse_decoder_thread(
     CHUNK = 4096  # bytes per read (2048 samples at 16-bit mono)
     SCOPE_INTERVAL = 0.1  # scope updates at ~10 Hz
     last_scope = time.monotonic()
+    waiting_since: float | None = None
 
     decoder = MorseDecoder(
         sample_rate=sample_rate,
@@ -293,6 +294,8 @@ def morse_decoder_thread(
             if not ready:
                 # No data from SDR — emit diagnostic heartbeat
                 now = time.monotonic()
+                if waiting_since is None:
+                    waiting_since = now
                 if now - last_scope >= SCOPE_INTERVAL:
                     last_scope = now
                     with contextlib.suppress(queue.Full):
@@ -302,12 +305,14 @@ def morse_decoder_thread(
                             'threshold': 0,
                             'tone_on': False,
                             'waiting': True,
+                            'waiting_seconds': round(now - waiting_since, 1),
                         })
                 continue
 
             data = os.read(fd, CHUNK)
             if not data:
                 break
+            waiting_since = None
 
             events = decoder.process_block(data)