Split span zoom from sample rate control

cmd/sdrd/main.go

@@ -363,6 +363,7 @@ func runDSP(ctx context.Context, src sdr.Source, cfg config.Config, det *detecto
 	dcEnabled := cfg.DCBlock
 	iqEnabled := cfg.IQBalance
 
+	gotSamples := false
 	for {
 		select {
 		case <-ctx.Done():
@@ -385,6 +386,10 @@ func runDSP(ctx context.Context, src sdr.Source, cfg config.Config, det *detecto
 				log.Printf("read IQ: %v", err)
 				continue
 			}
+			if !gotSamples {
+				log.Printf("received IQ samples")
+				gotSamples = true
+			}
 			if dcEnabled {
 				dcBlocker.Apply(iq)
 			}

internal/sdrplay/sdrplay.go

@@ -70,6 +70,7 @@ import (
 	"fmt"
 	"runtime/cgo"
 	"sync"
+	"time"
 	"unsafe"
 
 	"sdr-visual-suite/internal/sdr"
@@ -134,6 +135,11 @@ func (s *Source) configure(sampleRate int, centerHz float64, gainDb float64) err
 	if err := cErr(C.sdrplay_api_Init(s.dev.dev, &cb, unsafe.Pointer(uintptr(s.handle)))); err != nil {
 		return fmt.Errorf("sdrplay_api_Init: %w", err)
 	}
+	// Apply initial settings explicitly to ensure streaming starts.
+	updateReasons := C.int(C.sdrplay_api_Update_Dev_Fs | C.sdrplay_api_Update_Tuner_Frf | C.sdrplay_api_Update_Tuner_Gr | C.sdrplay_api_Update_Ctrl_Agc)
+	if err := cErr(C.sdrplay_update(unsafe.Pointer(s.dev.dev), updateReasons)); err != nil {
+		return fmt.Errorf("sdrplay_api_Update: %w", err)
+	}
 	return nil
 }
 
@@ -200,11 +206,15 @@ func (s *Source) Stop() error {
 }
 
 func (s *Source) ReadIQ(n int) ([]complex64, error) {
-	buf := <-s.ch
-	if len(buf) >= n {
-		return buf[:n], nil
+	select {
+	case buf := <-s.ch:
+		if len(buf) >= n {
+			return buf[:n], nil
+		}
+		return buf, nil
+	case <-time.After(1500 * time.Millisecond):
+		return nil, errors.New("timeout waiting for IQ samples")
 	}
-	return buf, nil
 }
 
 //export goStreamCallback

web/app.js

@@ -16,6 +16,7 @@ const detailSpectrogram = document.getElementById('detailSpectrogram');
 const configStatusEl = document.getElementById('configStatus');
 const centerInput = document.getElementById('centerInput');
 const spanInput = document.getElementById('spanInput');
+const sampleRateSelect = document.getElementById('sampleRateSelect');
 const fftSelect = document.getElementById('fftSelect');
 const gainRange = document.getElementById('gainRange');
 const gainInput = document.getElementById('gainInput');
@@ -87,7 +88,11 @@ function applyConfigToUI(cfg) {
   if (!cfg) return;
   isSyncingConfig = true;
   centerInput.value = toMHz(cfg.center_hz).toFixed(6);
-  spanInput.value = toMHz(cfg.sample_rate).toFixed(3);
+  if (sampleRateSelect) {
+    sampleRateSelect.value = toMHz(cfg.sample_rate).toFixed(3).replace(/\.0+$/, '').replace(/\.$/, '');
+  }
+  const spanMHz = toMHz(cfg.sample_rate / zoom);
+  spanInput.value = spanMHz.toFixed(3);
   fftSelect.value = String(cfg.fft_size);
   gainRange.value = cfg.gain_db;
   gainInput.value = cfg.gain_db;
@@ -214,6 +219,9 @@ function renderSpectrum() {
   const span = sample_rate / zoom;
   const startHz = center_hz - span / 2 + pan * span;
   const endHz = center_hz + span / 2 + pan * span;
+  if (!isSyncingConfig && spanInput) {
+    spanInput.value = (span / 1e6).toFixed(3);
+  }
 
   const minDb = -120;
   const maxDb = 0;
@@ -465,11 +473,22 @@ centerInput.addEventListener('change', () => {
 
 spanInput.addEventListener('change', () => {
   const mhz = parseFloat(spanInput.value);
-  if (Number.isFinite(mhz) && mhz > 0) {
-    queueConfigUpdate({ sample_rate: Math.round(fromMHz(mhz)) });
-  }
+  if (!Number.isFinite(mhz) || mhz <= 0) return;
+  const baseRate = currentConfig ? currentConfig.sample_rate : (latest ? latest.sample_rate : 0);
+  if (!baseRate) return;
+  zoom = Math.max(0.25, Math.min(20, baseRate / fromMHz(mhz)));
+  timelineDirty = true;
 });
 
+if (sampleRateSelect) {
+  sampleRateSelect.addEventListener('change', () => {
+    const mhz = parseFloat(sampleRateSelect.value);
+    if (Number.isFinite(mhz) && mhz > 0) {
+      queueConfigUpdate({ sample_rate: Math.round(fromMHz(mhz)) });
+    }
+  });
+}
+
 fftSelect.addEventListener('change', () => {
   const size = parseInt(fftSelect.value, 10);
   if (Number.isFinite(size)) {

web/index.html

@@ -30,7 +30,20 @@
 
         <label class="control-label" for="spanInput">Span (MHz)</label>
         <div class="control-row">
-          <input id="spanInput" type="number" step="0.1" min="0.1" />
+          <input id="spanInput" type="number" step="0.05" min="0.05" />
+        </div>
+
+        <label class="control-label" for="sampleRateSelect">Sample Rate (MHz)</label>
+        <div class="control-row">
+          <select id="sampleRateSelect">
+            <option value="0.5">0.5</option>
+            <option value="1.0">1.0</option>
+            <option value="1.536">1.536</option>
+            <option value="2.048">2.048</option>
+            <option value="2.5">2.5</option>
+            <option value="3.072">3.072</option>
+            <option value="4.096">4.096</option>
+          </select>
         </div>
 
         <label class="control-label" for="fftSelect">FFT Size</label>