fix: redefines rectime_seconds from strt[18] byte to new computed time.

The server now re-computes rectime_seconds using the actual sample rate from the compliance config (overriding the default 1024 in the client), so if the device runs at 2048 or 4096 sps it's still correct.

Viewer — The rectime display now shows Xs (stored) / Ys (cfg) so you can compare the STRT-derived duration against the compliance config's record_time setting side-by-side. I also clamped the y-axis to ±(0C peak × 1.4) so near-saturation decode artifacts don't squash the real blast signal into a flat line.

sfm/server.py

@@ -689,13 +689,22 @@ def device_event_waveform(
     if sample_rate is None and info.compliance_config:
         sample_rate = info.compliance_config.sample_rate
 
+    # Recompute rectime_seconds using the actual sample rate now that we have it.
+    # _decode_a5_waveform used 1024 sps as default; override if device says otherwise.
+    # strt[18] is a record-mode byte (0x46 / 0x0E), NOT rectime in seconds.
+    rectime_seconds = ev.rectime_seconds
+    if (ev.total_samples is not None and ev.pretrig_samples is not None
+            and sample_rate and sample_rate > 0):
+        post_trig = max(0, ev.total_samples - ev.pretrig_samples)
+        rectime_seconds = round(post_trig / sample_rate, 2)
+
     result = {
         "index":           ev.index,
         "record_type":     ev.record_type,
         "timestamp":       _serialise_timestamp(ev.timestamp),
         "total_samples":   ev.total_samples,
         "pretrig_samples": ev.pretrig_samples,
-        "rectime_seconds": ev.rectime_seconds,
+        "rectime_seconds": rectime_seconds,
         "samples_decoded": samples_decoded,
         "sample_rate":     sample_rate,
         "peak_values":     _serialise_peak_values(ev.peak_values),

sfm/waveform_viewer.html

@@ -193,6 +193,10 @@
   </div>
   <button id="connect-btn" onclick="connectUnit()">Connect</button>
   <button id="load-btn" onclick="loadWaveform()" disabled>Load Waveform</button>
+  <label style="display:flex;align-items:center;gap:4px;color:#8b949e;font-size:12px;cursor:pointer">
+    <input type="checkbox" id="force-reload" style="accent-color:#1f6feb" />
+    Force&nbsp;reload
+  </label>
   <button id="prev-btn" onclick="stepEvent(-1)" disabled>◀ Prev</button>
   <button id="next-btn" onclick="stepEvent(+1)" disabled>Next ▶</button>
 </header>
@@ -404,7 +408,8 @@
     btn.disabled = true;
     setStatus('Fetching waveform…', 'loading');
 
-    const url = `${apiBase}/device/event/${evIndex}/waveform?host=${encodeURIComponent(devHost)}&tcp_port=${tcpPort}`;
+    const force = document.getElementById('force-reload')?.checked ? '&force=true' : '';
+    const url = `${apiBase}/device/event/${evIndex}/waveform?host=${encodeURIComponent(devHost)}&tcp_port=${tcpPort}${force}`;
 
     let data;
     try {
@@ -456,7 +461,14 @@
     appendMeta('sr', `${sr} sps`);
     appendMeta('samples', `${decoded.toLocaleString()} / ${total.toLocaleString()}`);
     appendMeta('pretrig', pretrig);
-    appendMeta('rectime', `${data.rectime_seconds ?? '?'}s`);
+    // rectime_seconds is computed from (total_samples - pretrig_samples) / sr in
+    // _decode_a5_waveform.  Also show the compliance config record_time for reference.
+    const cfgRt = unitInfo?.compliance_config?.record_time;
+    const strtRt = data.rectime_seconds;
+    const rtStr = (strtRt !== null && strtRt !== undefined)
+      ? `${strtRt}s (stored)` + (cfgRt !== null && cfgRt !== undefined ? ` / ${cfgRt}s (cfg)` : '')
+      : (cfgRt !== null && cfgRt !== undefined ? `${cfgRt}s (cfg)` : '?');
+    appendMeta('rectime', rtStr);
 
     // No waveform data — show a clear reason instead of empty charts
     if (decoded === 0) {
@@ -490,6 +502,13 @@
     const micPeakPsi = data.peak_values?.micl_psi ?? null;
     const DBL_REF_PSI = 2.9e-9; // 20 µPa in psi
 
+    // 0C record peak values (device-computed, authoritative) per channel
+    const peakValues0C = {
+      Tran: data.peak_values?.tran_in_s ?? null,
+      Vert: data.peak_values?.vert_in_s ?? null,
+      Long: data.peak_values?.long_in_s ?? null,
+    };
+
     for (const [ch, color] of Object.entries(CHANNEL_COLORS)) {
       const samples = channels[ch];
       if (!samples || samples.length === 0) continue;
@@ -500,9 +519,16 @@
 
       if (isGeo) {
         // Geo channels: counts × (range / 32767) → in/s
+        // Scale factor for the waveform shape (may need calibration per unit)
         const scale = geoRange / 32767;
         plotSamples = samples.map(c => c * scale);
-        const peakIns = Math.max(...plotSamples.map(Math.abs));
+
+        // Use the device-computed 0C record peak for the label (authoritative).
+        // The raw-sample-computed peak can be inflated by frame-boundary artifacts.
+        const peak0C = peakValues0C[ch];
+        const peakIns = (peak0C !== null && peak0C !== undefined)
+          ? peak0C
+          : Math.max(...plotSamples.map(Math.abs));
         peakLabel  = `${peakIns.toFixed(5)} in/s`;
         yUnit      = 'in/s';
         tooltipFmt = v => `${ch}: ${v.toFixed(5)} in/s`;
@@ -586,6 +612,14 @@
               grid: { color: '#21262d' },
             },
             y: {
+              // Clamp geo-channel y-axis to ±(0C peak × 1.4) so near-saturation
+              // decode artifacts (which inflate autoscale to full range) don't
+              // squash the actual blast signal into an invisible flat line.
+              // The 0C peak value is authoritative for the true signal amplitude.
+              ...(isGeo && peak0C !== null && peak0C > 0 ? {
+                min: -(peak0C * 1.4),
+                max:  (peak0C * 1.4),
+              } : {}),
               ticks: {
                 color: '#484f58',
                 maxTicksLimit: 5,