feat: Icom split auto

internal/cat/icomserial.go

@@ -615,8 +615,22 @@ func (b *IcomSerial) scopeLoop(spec chan civ.Decoded, done chan struct{}) {
 				// edges and take the rest as the trace, then publish immediately.
 				// (USB splits this across 21 frames; the net rig sends it as one.)
 				if len(region) >= 11 {
-					low := civ.BCDToFreq(region[1:6])
-					high := civ.BCDToFreq(region[6:11])
+					// Net single-frame layout (IC-7610): region = [info 1B][freq1 5-BCD]
+					// [freq2 5-BCD][amplitude bytes]. The two freq fields depend on the
+					// scope mode: FIXED sends [low-edge][high-edge] (both absolute), CENTRE
+					// sends [centre][span]. Tell them apart by magnitude — a second value
+					// BIGGER than the first is a real high edge; a small one is a span
+					// (e.g. 14.200 MHz + 100 kHz → centred 14.150-14.250; 21.000 +
+					// 21.070 → fixed 21.000-21.070). Guessing wrong here gave the absurd
+					// 21.000-42.070 span (low + a 21 MHz "span").
+					v1 := civ.BCDToFreq(region[1:6])
+					v2 := civ.BCDToFreq(region[6:11])
+					var low, high int64
+					if v2 > v1 {
+						low, high = v1, v2 // absolute low/high edges (fixed edge set)
+					} else {
+						low, high = v1-v2/2, v1+v2/2 // centre + span (centre-on-VFO)
+					}
 					amp := append([]byte(nil), region[11:]...)
 					b.scopeMu.Lock()
 					b.scopeLow, b.scopeHigh = low, high
@@ -627,10 +641,10 @@ func (b *IcomSerial) scopeLoop(spec chan civ.Decoded, done chan struct{}) {
 					b.scopeMu.Unlock()
 					if firstLog {
 						head := region
-						if len(head) > 24 {
-							head = head[:24]
+						if len(head) > 16 {
+							head = head[:16]
 						}
-						applog.Printf("icom scope (net 1-frame): region=%dB head=[% X] → edges %d..%d Hz points=%d", len(region), head, low, high, len(amp))
+						applog.Printf("icom scope (net 1-frame): head=[% X] v1=%d v2=%d → %d..%d Hz points=%d", head, v1, v2, low, high, len(amp))
 					}
 				}
 				continue
@@ -1356,6 +1370,24 @@ func (b *IcomSerial) SetMicGain(p int) error {
 }
 
 func (b *IcomSerial) SetIcomSplit(on bool) error {
+	if on {
+		// Enable split with the usual "work him up" TX offset: +1 kHz on CW,
+		// +5 kHz otherwise (SSB). Set the unselected (TX) VFO to RX+offset first,
+		// then turn split on. 0x25 0x01 + BCD sets the unselected VFO's frequency.
+		rx := b.curFreq
+		if rx <= 0 {
+			if hz, err := b.readFreq(); err == nil {
+				rx = hz
+			}
+		}
+		if rx > 0 {
+			offset := int64(5000)
+			if b.curModeByte == civ.ModeCW || b.curModeByte == civ.ModeCWR {
+				offset = 1000
+			}
+			_ = b.exec(append([]byte{civ.CmdVfoFreq, civ.SubVfoUnselected}, civ.FreqToBCD(rx+offset)...)...)
+		}
+	}
 	if err := b.exec(civ.CmdSplit, boolByte(on)); err != nil {
 		return err
 	}