Restore SX1276 CW support and calibrated power sweeps

Retain the original carrier feature from PR #11 with zero-deviation FSK, board PA calibration, and LoRa restoration. Re-key after power changes without extending the timeout, and restore prior power after a failed sweep. Cover native and SX1276 transitions, failure recovery, external PA and RFO mapping; verify Linkflow repeater and Heltec V2 USB Companion builds.

src/helpers/radiolib/CustomSX1276Wrapper.h

@@ -10,8 +10,12 @@
 class CustomSX1276Wrapper : public RadioLibWrapper {
 public:
   CustomSX1276Wrapper(CustomSX1276& radio, mesh::MainBoard& board) : RadioLibWrapper(radio, board) { }
+  bool supportsCarrierWave() const override { return supportsRadioDeepInit(); }
 
-  void powerOff() { _radio->standby(); _radio->sleep(); }
+  void powerOff() {
+    if (isCarrierWaveActive()) setCarrierWave(0, 0);
+    _radio->standby(); _radio->sleep();
+  }
 
 protected:
   bool applyParams(float freq, float bw, uint8_t sf, uint8_t cr) override {
@@ -24,6 +28,7 @@ protected:
 
 public:
   bool setCodingRate(uint8_t cr) override {
+    if (isCarrierWaveActive()) return false;
     return ((CustomSX1276 *)_radio)->setCodingRate(cr) == RADIOLIB_ERR_NONE;
   }
 
@@ -40,6 +45,28 @@ public:
   uint8_t getSpreadingFactor() const override { return ((CustomSX1276 *)_radio)->spreadingFactor; }
 
 protected:
+  int16_t enterCarrierWave() override {
+    auto* radio = static_cast<CustomSX1276*>(_radio);
+    // Direct TX needs FSK. Zero deviation prevents a floating DIO2 data input
+    // from moving the carrier. Start at the PA_BOOST floor, while still idle;
+    // user-facing power may be an external PA level, not chip drive power.
+    int16_t status = radio->beginFSK(_cur_freq, 4.8, 0.0, 125.0, 2, 16, false);
+    if (status != RADIOLIB_ERR_NONE) return status;
+#ifdef SX127X_CURRENT_LIMIT
+    status = radio->setCurrentLimit(SX127X_CURRENT_LIMIT);
+    if (status != RADIOLIB_ERR_NONE) return status;
+#endif
+    status = applyCachedTxPower(_dbm_valid ? _cur_dbm : LORA_TX_POWER);
+    if (status != RADIOLIB_ERR_NONE) return status;
+    return radio->transmitDirect();
+  }
+
+  bool restoreCarrierWaveModem() override {
+    // Restores LoRa, runtime profile/preamble, IRQ mapping and PA calibration.
+    // Shared cleanup retains the stop/retry guard if any restoration fails.
+    return restoreAfterDeepInit();
+  }
+
   int16_t performChannelScan() override {
     return ((CustomSX1276 *)_radio)->tryScanChannel(cadScanTimeoutMillis(), *_board);
   }

src/helpers/radiolib/RadioLibWrappers.cpp

@@ -89,6 +89,23 @@ uint32_t RadioLibWrapper::getRngSeed() {
 }
 
 bool RadioLibWrapper::setTxPower(int8_t dbm) {
+  if (_cw_active) {
+    if (_cw_stopping) return false;
+    // Permit meter sweeps through the board's normal power/PA calibration.
+    // SX127x's power setter enters standby, so re-key without resetting the
+    // modem or extending the original CW deadline.
+    if (applyCachedTxPower(dbm) != RADIOLIB_ERR_NONE) {
+      stopCarrierWave();
+      return false;
+    }
+    if (_radio->transmitDirect() != RADIOLIB_ERR_NONE) {
+      stopCarrierWave();
+      return false;
+    }
+    _cur_dbm = dbm;
+    _dbm_valid = true;
+    return true;
+  }
   const uint8_t resume_rx = beginReconfigure();
   if (resume_rx > 1) return false;
 
@@ -707,7 +724,7 @@ mesh::RadioParamApplyResult RadioLibWrapper::setCarrierWave(uint8_t profile, uin
   _board->setRadioTestActive(true);  // service the deadline even without USB
   _board->onBeforeTransmit();
   _cw_board_tx = true;
-  if (_radio->transmitDirect() != RADIOLIB_ERR_NONE) {
+  if (enterCarrierWave() != RADIOLIB_ERR_NONE) {
     stopCarrierWave();  // a failed SPI result does not prove TX stayed off
     return Result::FAILED;
   }
@@ -717,11 +734,13 @@ mesh::RadioParamApplyResult RadioLibWrapper::setCarrierWave(uint8_t profile, uin
 
 bool RadioLibWrapper::stopCarrierWave() {
   _cw_stopping = true;
-  // finishTransmit clears radio IRQs and enters standby on both supported
-  // families. Deassert external TX even if SPI fails, then try a radio reset.
+  // Deassert external TX even if SPI fails. SX127x must also rebuild its LoRa
+  // modem after FSK direct mode before normal packet work can resume.
   const int16_t status = _radio->finishTransmit();
   if (_cw_board_tx) { _board->onAfterTransmit(); _cw_board_tx = false; }
-  if (status != RADIOLIB_ERR_NONE && !restoreAfterDeepInit()) {
+  const bool restored = status == RADIOLIB_ERR_NONE
+      ? restoreCarrierWaveModem() : restoreAfterDeepInit();
+  if (!restored) {
     _cw_retry_at = static_cast<uint32_t>(millis()) + 100;
     return false;  // hold normal work until stopping the carrier is confirmed
   }

src/helpers/radiolib/RadioLibWrappers.h

@@ -157,6 +157,12 @@ protected:
     return _radio->setOutputPower(dbm);
   }
   virtual bool applyRxBoostedGainMode(bool) { return false; }
+  virtual int16_t enterCarrierWave() { return _radio->transmitDirect(); }
+  // Native-CW radios keep their modem. Reapply cached power in case a meter
+  // sweep failed halfway through; SX127x also rebuilds its LoRa configuration.
+  virtual bool restoreCarrierWaveModem() {
+    return !_dbm_valid || applyCachedTxPower(_cur_dbm) == RADIOLIB_ERR_NONE;
+  }
   // Dual-profile scanning already suspends RXPS. Supported radios can also
   // retain their oscillator across the intervening standby/reconfigure steps.
   // Called only at the safe scan-mode entry/exit boundary, not during a packet.