feat: added RIT and XIT for Icom

internal/cat/icomserial.go

@@ -277,6 +277,12 @@ func (b *IcomSerial) SetPTT(on bool) error {
 // ── helpers ───────────────────────────────────────────────────────────────
 
 func (b *IcomSerial) write(payload ...byte) error {
+	// Not connected (rig off / port dropped): fail cleanly instead of
+	// dereferencing a nil port — a Set* dispatched while disconnected (e.g.
+	// clicking Scope ON with the radio off) would otherwise panic the app.
+	if b.port == nil {
+		return fmt.Errorf("icom: not connected")
+	}
 	// Drop any stale/unsolicited frames buffered from before this command so
 	// recv() only sees the reply to THIS request (avoids a previous command's ack
 	// or an unsolicited dial-turn update being mistaken for our response).
@@ -514,6 +520,68 @@ func (b *IcomSerial) SetScopeMode(fixed bool) error {
 	return nil
 }
 
+// SetRIT sets the RIT/ΔTX offset (signed Hz, ±9999).
+func (b *IcomSerial) SetRIT(hz int) error {
+	if err := b.exec(append([]byte{civ.CmdRIT, civ.SubRITFreq}, civ.RITToBCD(hz)...)...); err != nil {
+		return err
+	}
+	if hz < -9999 {
+		hz = -9999
+	}
+	if hz > 9999 {
+		hz = 9999
+	}
+	b.setCache(func(s *IcomTXState) { s.RITHz = hz })
+	return nil
+}
+
+func (b *IcomSerial) SetRITOn(on bool) error {
+	if err := b.exec(civ.CmdRIT, civ.SubRITOn, boolByte(on)); err != nil {
+		return err
+	}
+	b.setCache(func(s *IcomTXState) { s.RITOn = on })
+	return nil
+}
+
+func (b *IcomSerial) SetXITOn(on bool) error {
+	if err := b.exec(civ.CmdRIT, civ.SubXITOn, boolByte(on)); err != nil {
+		return err
+	}
+	b.setCache(func(s *IcomTXState) { s.XITOn = on })
+	return nil
+}
+
+// readRIT reads the offset + RIT/ΔTX on-off flags into st (best-effort).
+func (b *IcomSerial) readRIT(st *IcomTXState) {
+	if err := b.write(civ.CmdRIT, civ.SubRITFreq); err == nil {
+		if f, err := b.recv(icomDSPTimeout, func(d civ.Decoded) bool {
+			return d.Cmd == civ.CmdRIT && len(d.Data) >= 4 && d.Data[0] == civ.SubRITFreq
+		}); err == nil {
+			st.RITHz = civ.BCDToRIT(f.Data[1:4])
+		}
+	}
+	if v, ok := b.readSwitchSub(civ.CmdRIT, civ.SubRITOn); ok {
+		st.RITOn = v != 0
+	}
+	if v, ok := b.readSwitchSub(civ.CmdRIT, civ.SubXITOn); ok {
+		st.XITOn = v != 0
+	}
+}
+
+// readSwitchSub reads a 1-byte on/off value for cmd+sub (generalises readSwitch).
+func (b *IcomSerial) readSwitchSub(cmd, sub byte) (byte, bool) {
+	if err := b.write(cmd, sub); err != nil {
+		return 0, false
+	}
+	f, err := b.recv(icomDSPTimeout, func(d civ.Decoded) bool {
+		return d.Cmd == cmd && len(d.Data) >= 2 && d.Data[0] == sub
+	})
+	if err != nil {
+		return 0, false
+	}
+	return f.Data[1], true
+}
+
 // ScopeData returns a copy of the latest reassembled sweep as a number array.
 func (b *IcomSerial) ScopeData() ScopeSweep {
 	b.scopeMu.Lock()
@@ -743,6 +811,7 @@ func (b *IcomSerial) readDSP() {
 	if _, f, ok := b.readModeFilter(); ok {
 		st.Filter = int(f)
 	}
+	b.readRIT(&st)
 
 	b.dspMu.Lock()
 	b.dsp = st