Make Rxdutycycling Great Again

zephcore/ARCHITECTURE.md

@@ -364,7 +364,7 @@ The custom `lr11xx_lora.c` driver handles several LR1110 firmware bugs:
 - **RX buffer drift**: Buffer base shifts 4 bytes per packet → `clear_rxbuffer()` after every RX
 - **Header error**: Can shift buffer pointer → standby before RX restart
 - **DIO1 stuck HIGH**: 5-cycle detection → full hardware reset + recovery
-- **RX duty cycle broken**: 23-40% packet loss → disabled, always continuous RX
+- **RX duty cycle**: wired via `SetRxDutyCycle` MODE_RX, sized by the shared adapter math (same as SX126x). The earlier "broken, 23-40% loss" verdict was a window-sizing bug (over-sleep + no header budget), not a chip defect — default-off, HW-verify before production use.
 
 ### 5.5 Default Radio Parameters
 

zephcore/Kconfig

@@ -485,27 +485,54 @@ config ZEPHCORE_LORA_RX_DUTY_CYCLE
 	bool "Enable LoRa RX duty cycle power saving"
 	default n
 	help
-	  Enable RX duty cycling for power saving on battery-powered devices.
-	  Uses RadioLib's algorithm to calculate optimal timing based on SF/BW.
+	  Enable RX duty cycling (chip-autonomous sniff mode) for power
+	  saving on battery-powered devices.  This sets the boot default;
+	  it can be toggled at runtime via CLI "set rxduty on/off".
 
-	  Disabled by default for all roles. Enable manually if you want
-	  power savings and have verified acceptable packet loss/latency for
-	  your environment and radio.
-	  Duty cycle mode also resets AGC state after every received
-	  packet via Calibrate(ALL), preventing the "near-far" gain-lock
-	  problem where a strong signal desensitises the receiver.
-	  Still disabled for LR1110 (cannot lock on mid-preamble, causes packet
-	  loss) and LR2021 (untested — enable manually after verifying no
-	  packet loss).  Can be toggled at runtime via CLI.
+	  Window timing is computed per SF/BW/preamble from primary-source
+	  constraints (SX1261/2 datasheet sec 13.1.7, AN1200.36): the deaf
+	  time per cycle (sleep + TCXO/PLL wake transition) never exceeds
+	  the budget needed to guarantee one full detection window inside
+	  the sender's preamble, and the post-detect timer budget
+	  (2*rxPeriod + sleepPeriod) always covers preamble + header.
+	  With a 32-symbol sender preamble (current MeshCore firmware at
+	  SF<=8) this yields ~40-55% radio-off time with zero loss against
+	  updated senders.  Presets whose preamble is too short for a
+	  guaranteed catch (16 symbols at SF>=9) automatically fall back to
+	  continuous RX — no fake duty cycling.
 
-	  The key insight is that LoRa preamble symbols are all identical,
-	  so CAD/RX can detect preamble even if we wake mid-stream. The
-	  algorithm ensures we always catch at least 8 symbols regardless
-	  of when we wake within the preamble window.
+	  Caveat for mixed meshes: nodes still on pre-preamble-32 firmware
+	  (16 symbols at SF<=8) are only caught ~50% worst-phase.  Keep
+	  this off on infrastructure until the local mesh has converted.
+	  Floods are usually re-heard via updated repeaters; direct
+	  messages from legacy nodes are the real exposure.
 
-	  Power savings: ~60-70% reduction in RX current (10-15mA to 3-5mA).
+	  Duty cycle mode also resets AGC state on entry via
+	  Calibrate(ALL), pins the boosted RX gain into the warm-start
+	  retention list (datasheet sec 9.6, mandatory for SetRxDutyCycle),
+	  and runs a parked-RX watchdog that re-arms the cycle after a
+	  false preamble detect (inspect via CLI "get dc.restarts").
 
-	  Can be toggled at runtime via CLI "set rxduty on/off".
+	  LR1110/LR20xx use the same chip-level SetRxDutyCycle MODE_RX
+	  (identical preamble-detect-and-extend mechanism) sized by the same
+	  adapter math; the LR1110's earlier "broken" status was a window-
+	  sizing bug, not a chip defect. Both are wired but HW-unverified —
+	  confirm no packet loss on a live board before trusting in
+	  production. LR1110 has no infinite-park failure mode (its DC uses a
+	  bounded 2*rx+sleep timeout), so it re-arms via the normal RX-timeout
+	  path rather than the SX126x watchdog.
+
+config ZEPHCORE_LORA_DC_MIN_SYMBOLS
+	int "RX duty cycle: preamble symbols required for detection"
+	range 4 16
+	default 8
+	help
+	  Minimum LoRa preamble symbols that must land inside one open RX
+	  window for detection to be considered guaranteed.  8 is Semtech's
+	  own figure for sniff mode (AN1200.36 sec 4); their time-synced
+	  LoRaWAN stacks budget 6.  Raise to 10-12 to trade radio-off time
+	  for extra detection margin on very noisy sites.  SF5/6 adds +4
+	  internally.  Lowering below 8 risks missed packets at low SNR.
 
 config ZEPHCORE_APC
 	bool "Adaptive Power Control (APC)"

zephcore/Repeater_CLI_commands.md

@@ -201,7 +201,7 @@ All `set uplink.*` changes are saved immediately and only applied after reboot.
 | `get loop.detect` | Loop detection level: `off`, `minimal`, `moderate`, or `strict` |
 | `get radio.rxgain` | RX gain boost: `0` or `1` |
 | `get rxduty` | RX duty cycle mode: `0` or `1` |
-| `get dc.restarts` | Duty-cycle preamble false-positive re-arm counter. High values mean the preamble detector is tripping on noise/interference without real packets arriving — inflates RX-on time and drains battery. Reset by `clear stats`. |
+| `get dc.restarts` | Duty-cycle preamble false-positive re-arm counter (RxTimeout re-arms + parked-RX watchdog recoveries). High values mean the preamble detector is tripping on noise/interference without real packets arriving — inflates RX-on time and drains battery; packets are never lost to it. Reset by `clear stats`. |
 | `get adc.multiplier` | Battery voltage ADC calibration multiplier |
 | `get bootloader.ver` | Bootloader version string |
 | `get public.key` | *(USB only)* Node's public key as hex |
@@ -243,7 +243,7 @@ Changes are persisted immediately unless noted. Some require a reboot.
 | `set path.hash.mode <mode>` | 0, 1, or 2 | Path hashing algorithm |
 | `set loop.detect <mode>` | `off`, `minimal`, `moderate`, `strict` | Loop detection sensitivity |
 | `set radio.rxgain <0\|1\|on\|off>` | | RX gain boost *(reboot required)* |
-| `set rxduty <0\|1\|on\|off>` | | RX duty cycle mode *(reboot required)* |
+| `set rxduty <0\|1\|on\|off>` | | RX duty cycle mode *(reboot required)*. Window timing auto-sized per SF/BW/preamble from the SX126x datasheet constraints (boot log line `rxduty:` shows the result). Zero-loss guarantee assumes senders on preamble-32 firmware (current MeshCore at SF≤8); legacy preamble-16 senders are only caught ~50% worst-phase — keep off until the local mesh has converted. Presets with 16-symbol preambles (SF≥9) fall back to continuous RX automatically. |
 | `set adc.multiplier <mult>` | (0 = use board default) | Battery voltage ADC calibration multiplier |
 | `set prv.key <hex>` | 64-char hex (32-byte key) | Replace private key; derive new identity *(reboot to apply)* |
 

zephcore/adapters/datastore/ZephyrDataStore.cpp

@@ -533,6 +533,16 @@ void ZephyrDataStore::loadPrefs(NodePrefs &prefs)
 	} else {
 		prefs.auto_shutdown_mv = CONFIG_ZEPHCORE_AUTO_SHUTDOWN_MILLIVOLTS;
 	}
+
+	/* Offset 150: rx_duty_cycle (ZephCore extension).  Absent in pre-existing
+	 * files → leave the caller's in-RAM default (0 = continuous RX) untouched
+	 * so the no-op past-EOF read can't force it on. */
+	if (off < len) {
+		prefs.rx_duty_cycle = buf[off++];
+		if (prefs.rx_duty_cycle > 1) {
+			prefs.rx_duty_cycle = 0;
+		}
+	}
 }
 
 void ZephyrDataStore::savePrefs(const NodePrefs &prefs)
@@ -605,7 +615,9 @@ void ZephyrDataStore::savePrefs(const NodePrefs &prefs)
 	/* Offset 148: auto_shutdown_mv (ZephCore extension, 2 bytes LE) */
 	buf[off++] = prefs.auto_shutdown_mv & 0xFF;
 	buf[off++] = (prefs.auto_shutdown_mv >> 8) & 0xFF;
-	/* Total: 150 bytes */
+	/* Offset 150: rx_duty_cycle (ZephCore extension) */
+	buf[off++] = prefs.rx_duty_cycle;
+	/* Total: 151 bytes */
 
 	bool ok = atomicReplaceFile(PREFS_FILE, buf, off);
 	LOG_DBG("savePrefs: wrote %s, ok=%d (%d bytes), name='%.16s'",

zephcore/adapters/radio/LR1110Radio.cpp

@@ -79,4 +79,9 @@ void LR1110Radio::hwResetAGC()
 	lr11xx_reset_agc(_dev);
 }
 
+uint32_t LR1110Radio::hwWakeupTimeUs()
+{
+	return lr11xx_get_wakeup_time_us(_dev);
+}
+
 } /* namespace mesh */

zephcore/adapters/radio/LR1110Radio.h

@@ -28,6 +28,7 @@ protected:
 	bool hwIsReceiving() override;
 	void hwSetRxBoost(bool enable) override;
 	void hwResetAGC() override;
+	uint32_t hwWakeupTimeUs() override;
 };
 
 } /* namespace mesh */

zephcore/adapters/radio/LoRaRadioBase.cpp

@@ -23,8 +23,18 @@ static uint16_t preambleLengthForSF(uint8_t sf)
 	return (sf <= 8) ? 32 : 16;
 }
 
-static constexpr uint16_t RX_DUTY_RX_SYMBOLS = 13;
-static constexpr uint16_t RX_DUTY_SLEEP_SYMBOLS = 3;
+/* Minimum preamble symbols that must land inside one open duty-cycle RX
+ * window for guaranteed detection.  8 is Semtech's own figure for sniff
+ * mode (AN1200.36 §4: "8 symbols in LoRa make up the time required to
+ * ensure that the SX1261/2 detects a valid incoming packet"); their
+ * time-synced LoRaWAN stacks budget 6, so 8 already carries margin.
+ * SF5/6 need more symbols to reach sensitivity (RadioLib/LBM use 12). */
+static uint16_t rxDutyDetectSymbols(uint8_t sf)
+{
+	uint16_t d = CONFIG_ZEPHCORE_LORA_DC_MIN_SYMBOLS;
+
+	return (sf >= 7) ? d : (uint16_t)(d + 4);
+}
 
 /* ── Constructor ─────────────────────────────────────────────── */
 
@@ -39,6 +49,7 @@ LoRaRadioBase::LoRaRadioBase(const struct device *lora_dev, MainBoard &board,
 	  _rx_duty_cycle_enabled(IS_ENABLED(CONFIG_ZEPHCORE_LORA_RX_DUTY_CYCLE)),
 	  _rx_boost_enabled(true),
 	  _tx_power_reduction_db(0),
+	  _dc_last_rx_us(0), _dc_last_sleep_us(0),
 	  _config_cached(false),
 	  _has_radio_override(false),
 	  _override_freq(0), _override_bw(0),
@@ -421,32 +432,88 @@ void LoRaRadioBase::startReceive()
 	int ret;
 
 	if (_rx_duty_cycle_enabled) {
-		/* Fixed duty-cycle window for field validation.
-		 * Keep build-time tunable via constants above. */
+		/* Duty-cycle window sizing.  All constraints primary-sourced
+		 * (SX1261/2 DS rev 2.2 §13.1.7 + AN1200.36):
+		 *
+		 * 1. Catch — worst case is a preamble starting D−ε symbols
+		 *    before an RX window closes (detection aborts, must
+		 *    complete in the NEXT window), so the total deaf time per
+		 *    cycle (programmed sleep + wake transition) must satisfy
+		 *      sleep + trans ≤ (P − 2D − 1)·Tsym
+		 *    with 1 symbol margin for the chip's RC64k sleep timer.
+		 *    Stricter than AN1200.36's own "P ≥ sleep + D" model,
+		 *    which ignores the window-tail arrival case.
+		 * 2. Complete — DS: "Tpreamble + Theader ≤ 2·rxPeriod +
+		 *    sleepPeriod".  A preamble detected at its first symbols
+		 *    restarts the chip timer with 2R+S; that budget must cover
+		 *    the rest of the preamble + sync (4.25) + header (~8),
+		 *    rounded up to P + 14 symbols.  The driver also sets
+		 *    StopTimerOnPreamble, but this sizing keeps packets safe
+		 *    under either documented timer behaviour.
+		 * 3. Floor — rxPeriod ≥ (D+1)·Tsym so any single window can
+		 *    detect on its own.
+		 *
+		 * No viable sleep budget (short preamble, or the TCXO restart
+		 * eats it) → honest fall-through to continuous RX. */
 		struct lora_modem_config cfg;
 		buildModemConfig(cfg, false);
 
-		uint8_t sf = (uint8_t)cfg.datarate;
-		uint32_t bw_hz = bandwidth_to_hz(cfg.bandwidth);
-		float bw_khz = (float)bw_hz / 1000.0f;
-		if (bw_khz > 0.0f) {
-			uint32_t symbol_us = (uint32_t)((float)(1 << sf) * 1000.0f / bw_khz);
-			uint32_t rx_us = RX_DUTY_RX_SYMBOLS * symbol_us;
-			uint32_t sleep_us = RX_DUTY_SLEEP_SYMBOLS * symbol_us;
+		const uint8_t sf = (uint8_t)cfg.datarate;
+		const uint32_t bw_hz = bandwidth_to_hz(cfg.bandwidth);
+		const uint16_t P = cfg.preamble_len;
+		const uint16_t D = rxDutyDetectSymbols(sf);
 
-			ret = lora_recv_duty_cycle(_dev,
-						   K_USEC(rx_us),
-						   K_USEC(sleep_us),
-						   rxCallbackStatic, this);
-			if (ret == 0) {
-				atomic_set(&_in_recv_mode, 1);
-				return;
-			}
-			if (ret != -ENOSYS) {
-				LOG_ERR("lora_recv_duty_cycle failed: %d", ret);
+		if (bw_hz > 0 && P > 2 * D + 1) {
+			const uint32_t sym_us = (uint32_t)
+				(((uint64_t)(1U << sf) * 1000000ULL) / bw_hz);
+			const uint32_t trans_us = hwWakeupTimeUs();
+			const uint32_t deaf_us =
+				(uint32_t)(P - 2 * D - 1) * sym_us;
+
+			if (deaf_us > trans_us + 2000) {
+				const uint32_t sleep_us = deaf_us - trans_us;
+				const uint32_t complete_us =
+					(uint32_t)(P + 14) * sym_us;
+				uint32_t rx_us = (uint32_t)(D + 1) * sym_us;
+
+				if (complete_us > sleep_us &&
+				    rx_us < (complete_us - sleep_us + 1) / 2) {
+					rx_us = (complete_us - sleep_us + 1) / 2;
+				}
+
+				if (rx_us != _dc_last_rx_us ||
+				    sleep_us != _dc_last_sleep_us) {
+					_dc_last_rx_us = rx_us;
+					_dc_last_sleep_us = sleep_us;
+					LOG_INF("rxduty: rx=%ums sleep=%ums trans=%ums (P=%u D=%u, off=%u%%)",
+						rx_us / 1000, sleep_us / 1000,
+						trans_us / 1000, P, D,
+						(uint32_t)(((uint64_t)sleep_us * 100) /
+							   (rx_us + sleep_us + trans_us)));
+				}
+
+				ret = lora_recv_duty_cycle(_dev,
+							   K_USEC(rx_us),
+							   K_USEC(sleep_us),
+							   rxCallbackStatic, this);
+				if (ret == 0) {
+					atomic_set(&_in_recv_mode, 1);
+					return;
+				}
+				if (ret != -ENOSYS) {
+					LOG_ERR("lora_recv_duty_cycle failed: %d", ret);
+				}
+				/* Fall through to continuous RX */
+			} else if (_dc_last_rx_us != UINT32_MAX) {
+				_dc_last_rx_us = UINT32_MAX;
+				LOG_INF("rxduty: wake transition %uus exceeds deaf budget %uus — continuous RX",
+					trans_us, deaf_us);
 			}
+		} else if (_dc_last_rx_us != UINT32_MAX) {
+			_dc_last_rx_us = UINT32_MAX;
+			LOG_INF("rxduty: preamble %u too short for guaranteed catch (need >%u syms) — continuous RX",
+				P, 2 * D + 1);
 		}
-		/* Fall through to normal recv_async */
 	}
 
 	ret = lora_recv_async(_dev, rxCallbackStatic, this);

zephcore/adapters/radio/LoRaRadioBase.h

@@ -112,6 +112,13 @@ protected:
 	/** GPIO-only BUSY check (no SPI). Default false for chips without duty-cycle sleep. */
 	virtual bool hwIsChipBusy() { return false; }
 
+	/** Radio deaf time per duty-cycle wake transition (context restore +
+	 *  PLL lock + TCXO startup where fitted), in microseconds.  Counts
+	 *  against the duty-cycle preamble-catch budget: per SX126x DS rev 2.2
+	 *  §13.1.7 the TCXO startup delay is inserted between the sleep and RX
+	 *  periods, outside both.  Default suits XTAL parts (LR2021). */
+	virtual uint32_t hwWakeupTimeUs() { return 1500; }
+
 	/* Set to true by subclasses using the loramac-node driver backend.
 	 * Disables the direction-only fast path in configureTx()/configureRx():
 	 * loramac-node calls Radio.SetTxConfig() and Radio.SetRxConfig() which
@@ -164,6 +171,12 @@ protected:
 	bool _rx_boost_enabled;
 	int8_t _tx_power_reduction_db;
 
+	/* Last duty-cycle timing handed to the driver — used to log timing
+	 * changes once at INF instead of on every RX restart.  0/0 = never
+	 * computed; UINT32_MAX rx = continuous-RX fallback active. */
+	uint32_t _dc_last_rx_us;
+	uint32_t _dc_last_sleep_us;
+
 	/* Config cache — skip redundant hwConfigure() */
 	struct lora_modem_config _last_cfg;
 	bool _config_cached;

zephcore/adapters/radio/SX126xRadio.cpp

@@ -91,6 +91,11 @@ bool SX126xRadio::hwIsChipBusy()
 	return sx126x_is_chip_busy(_dev);
 }
 
+uint32_t SX126xRadio::hwWakeupTimeUs()
+{
+	return sx126x_get_wakeup_time_us(_dev);
+}
+
 uint32_t SX126xRadio::getDutyCycleTimeoutRestarts() const
 {
 	return sx126x_get_dc_timeout_restarts(_dev);

zephcore/adapters/radio/SX126xRadio.h

@@ -31,6 +31,7 @@ protected:
 	void hwSetRxBoost(bool enable) override;
 	void hwResetAGC() override;
 	bool hwIsChipBusy() override;
+	uint32_t hwWakeupTimeUs() override;
 };
 
 } /* namespace mesh */

zephcore/app/RepeaterDataStore.cpp

@@ -241,12 +241,6 @@ bool RepeaterDataStore::loadPrefs(NodePrefs& prefs) {
         LOG_INF("loadPrefs: upgraded prefs format (%d -> 296 bytes)", (int)entry.size);
     }
 
-    /* One-time migration: disable RX duty cycle if it was previously enabled. */
-    if (prefs.rx_duty_cycle != 0) {
-        prefs.rx_duty_cycle = 0;
-        savePrefs(prefs);
-        LOG_INF("loadPrefs: migrated rx_duty_cycle to disabled");
-    }
     return true;
 }
 

zephcore/boards/example_board/README.md

@@ -259,7 +259,8 @@ should ONLY contain settings that can't be inferred from hardware:
     CONFIG_ZEPHCORE_UI_DISPLAY          Auto from DT zephyr,display chosen
     CONFIG_SPI                          Auto from ZEPHCORE_RADIO_LR1110
     CONFIG_NORDIC_QSPI_NOR             Auto from DT nordic,qspi-nor node
-    CONFIG_ZEPHCORE_LORA_RX_DUTY_CYCLE  Auto: ON for companion+SX1262, OFF for repeater/LR1110
+    CONFIG_ZEPHCORE_LORA_RX_DUTY_CYCLE  OFF by default for all roles (boot default only;
+                                        runtime toggle via CLI "set rxduty on/off")
     CONFIG_ESP_SPIRAM                   Auto: ON when DT psram0 size > 0 (ESP32-S/C5)
     CONFIG_ESP_SPIRAM_SIZE              Auto: read from DT psram0 size by upstream Kconfig
 

zephcore/patches/zephyr-new/drivers/lora/lr11xx/lr11xx_lora.c

@@ -79,10 +79,16 @@ struct lr11xx_data {
 	volatile bool in_rx_mode;
 
 	/* Extension features (duty cycle, boost) */
-	bool rx_duty_cycle_enabled; /* unused — LR1110 always continuous RX */
+	bool rx_duty_cycle_enabled;
 	bool rx_boost_enabled;
 	bool rx_boost_applied;  /* RX boost register written to hardware */
 
+	/* Stored duty-cycle timing from recv_duty_cycle() — the re-arm paths
+	 * (start_rx / restart_rx) reuse these exact values, never recompute:
+	 * window sizing is owned by the adapter layer (LoRaRadioBase). */
+	uint32_t dc_rx_ms;
+	uint32_t dc_sleep_ms;
+
 	/* CAD state */
 	lora_cad_cb cad_cb;
 	void *cad_user_data;
@@ -305,18 +311,33 @@ static void lr11xx_start_rx(struct lr11xx_data *data,
 	lr11xx_apply_modem_config(data, cfg, false);
 
 	/* Apply RX boost — persistent register, only written once.
-	 * Deferred from hw_init to here so radio is fully configured. */
-	if (data->rx_boost_enabled && !data->rx_boost_applied) {
+	 * Deferred from hw_init to here so radio is fully configured.
+	 * In duty-cycle mode we force a re-apply on every (re)start: the
+	 * chip's sleep-with-retention warm wakes are autonomous (no IRQ per
+	 * wake, so software can't intervene mid-cycle), and we don't want to
+	 * assume the boost register survives them — cheap insurance against
+	 * the SX126x-style silent -3 dB loss across warm starts. */
+	if (data->rx_boost_enabled &&
+	    (!data->rx_boost_applied || data->rx_duty_cycle_enabled)) {
 		lr11xx_radio_cfg_rx_boosted(ctx, true);
 		data->rx_boost_applied = true;
 	}
 
-	/* Start continuous RX.
-	 * 0xFFFFFF is the magic RTC-step value for continuous RX.
-	 * Must use the raw RTC-step API — set_rx() converts from ms,
-	 * which overflows uint32_t and gives a ~131 s timeout instead.
-	 * LR1110 always uses continuous RX (duty cycle is broken). */
-	lr11xx_radio_set_rx_with_timeout_in_rtc_step(ctx, 0xFFFFFF);
+	if (data->rx_duty_cycle_enabled &&
+	    data->dc_rx_ms != 0 && data->dc_sleep_ms != 0) {
+		/* Sniff mode: standard-RX listening with the chip's autonomous
+		 * sleep/wake.  MODE_RX uses the same preamble-detect-and-extend
+		 * (2*rx + sleep) mechanism as the SX126x — catches a preamble
+		 * mid-window.  Timing is computed by the adapter. */
+		lr11xx_radio_set_rx_duty_cycle(ctx, data->dc_rx_ms,
+			data->dc_sleep_ms, LR11XX_RADIO_RX_DUTY_CYCLE_MODE_RX);
+	} else {
+		/* Start continuous RX.
+		 * 0xFFFFFF is the magic RTC-step value for continuous RX.
+		 * Must use the raw RTC-step API — set_rx() converts from ms,
+		 * which overflows uint32_t and gives a ~131 s timeout instead. */
+		lr11xx_radio_set_rx_with_timeout_in_rtc_step(ctx, 0xFFFFFF);
+	}
 
 	/* LR1110 firmware sets CMD_ERROR IRQ flag on several write commands
 	 * (SetModParams, SetSyncWord, SetRxBoosted, SetRx) across all
@@ -345,9 +366,23 @@ static void lr11xx_restart_rx(struct lr11xx_data *data)
 	void *ctx = &data->hal_ctx;
 
 	lr11xx_system_clear_irq_status(ctx, LR11XX_SYSTEM_IRQ_ALL_MASK);
-	lr11xx_radio_set_rx_with_timeout_in_rtc_step(ctx, 0xFFFFFF);
 
-	/* RX boost persists through SetRx — no re-apply needed. */
+	if (data->rx_duty_cycle_enabled &&
+	    data->dc_rx_ms != 0 && data->dc_sleep_ms != 0) {
+		/* Re-arm sniff mode with the stored timing (e.g. after RX_DONE
+		 * or a false-preamble 2*rx+sleep timeout dropped the chip to
+		 * standby).  Re-apply boost — same warm-start caution as
+		 * start_rx. */
+		if (data->rx_boost_enabled) {
+			lr11xx_radio_cfg_rx_boosted(ctx, true);
+		}
+		lr11xx_radio_set_rx_duty_cycle(ctx, data->dc_rx_ms,
+			data->dc_sleep_ms, LR11XX_RADIO_RX_DUTY_CYCLE_MODE_RX);
+	} else {
+		lr11xx_radio_set_rx_with_timeout_in_rtc_step(ctx, 0xFFFFFF);
+		/* RX boost persists through SetRx — no re-apply needed. */
+	}
+
 	data->in_rx_mode = true;
 }
 
@@ -772,6 +807,61 @@ static int lr11xx_lora_recv_async(const struct device *dev,
 	return 0;
 }
 
+/* ── Driver API: recv_duty_cycle ─────────────────────────────────────── */
+
+static int lr11xx_lora_recv_duty_cycle(const struct device *dev,
+				       k_timeout_t rx_period,
+				       k_timeout_t sleep_period,
+				       lora_recv_cb cb, void *user_data)
+{
+	struct lr11xx_data *data = dev->data;
+	const struct lr11xx_config *cfg = dev->config;
+
+	/* NULL cb = cancel (same as recv_async cancel) */
+	if (cb == NULL) {
+		k_mutex_lock(&data->spi_mutex, K_FOREVER);
+		data->async_rx_cb = NULL;
+		data->async_rx_user_data = NULL;
+		data->rx_duty_cycle_enabled = false;
+		data->in_rx_mode = false;
+		k_mutex_unlock(&data->spi_mutex);
+		return 0;
+	}
+
+	if (!data->configured) {
+		return -EINVAL;
+	}
+
+	/* Explicit timing only — the adapter (LoRaRadioBase) owns the window
+	 * sizing.  No driver-side auto-compute. */
+	if (K_TIMEOUT_EQ(rx_period, K_FOREVER) ||
+	    K_TIMEOUT_EQ(sleep_period, K_FOREVER)) {
+		LOG_ERR("recv_duty_cycle: explicit rx/sleep periods required");
+		return -EINVAL;
+	}
+
+	uint32_t rx_ms = k_ticks_to_ms_ceil32(rx_period.ticks);
+	uint32_t slp_ms = k_ticks_to_ms_ceil32(sleep_period.ticks);
+	if (rx_ms < 1) rx_ms = 1;
+	if (slp_ms < 1) slp_ms = 1;
+
+	k_mutex_lock(&data->spi_mutex, K_FOREVER);
+
+	data->async_rx_cb = cb;
+	data->async_rx_user_data = user_data;
+	data->dc_rx_ms = rx_ms;
+	data->dc_sleep_ms = slp_ms;
+	data->rx_duty_cycle_enabled = true;
+
+	/* start_rx() reads rx_duty_cycle_enabled + dc_*_ms and issues
+	 * SetRxDutyCycle(MODE_RX) with a forced boost re-apply. */
+	lr11xx_start_rx(data, cfg);
+
+	k_mutex_unlock(&data->spi_mutex);
+	LOG_INF("recv_duty_cycle: rx=%ums sleep=%ums", rx_ms, slp_ms);
+	return 0;
+}
+
 /* ── Driver API: recv (sync) ─────────────────────────────────────────── */
 
 static int lr11xx_lora_recv(const struct device *dev, uint8_t *buf,
@@ -818,6 +908,21 @@ bool lr11xx_is_receiving(const struct device *dev)
 		       LR11XX_SYSTEM_IRQ_SYNC_WORD_HEADER_VALID)) != 0;
 }
 
+uint32_t lr11xx_get_wakeup_time_us(const struct device *dev)
+{
+	const struct lr11xx_config *cfg = dev->config;
+	/* Context restore + PLL lock (~1.5 ms) plus the TCXO startup delay
+	 * where fitted.  Per the LR11xx SetRxDutyCycle model the wake
+	 * transition is deaf time between sleep and RX, counting against the
+	 * adapter's preamble-catch budget — same accounting as the SX126x. */
+	uint32_t us = 1500;
+
+	if (cfg->tcxo_voltage_mv > 0) {
+		us += cfg->tcxo_startup_delay_ms * 1000U;
+	}
+	return us;
+}
+
 void lr11xx_set_rx_boost(const struct device *dev, bool enable)
 {
 	struct lr11xx_data *data = dev->data;
@@ -1203,7 +1308,12 @@ static DEVICE_API(lora, lr11xx_lora_api) = {
 	.recv_async = lr11xx_lora_recv_async,
 	.cad        = lr11xx_lora_cad,
 	.cad_async  = lr11xx_lora_cad_async,
-	/* .recv_duty_cycle = NULL — LR1110 duty cycle broken */
+	/* MODE_RX sniff: same preamble-detect-and-extend (2*rx+sleep) as the
+	 * SX126x.  The earlier "broken" verdict was a window-sizing bug
+	 * (over-sleep + no header budget), not a chip defect — now sized by
+	 * the shared adapter math.  Default-off via prefs; HW-verify on a
+	 * live LR1110 before trusting in production. */
+	.recv_duty_cycle = lr11xx_lora_recv_duty_cycle,
 };
 
 #define LR11XX_INIT(n)                                                     \

zephcore/patches/zephyr-new/drivers/lora/lr11xx/lr11xx_lora.h

@@ -50,6 +50,19 @@ bool lr11xx_is_receiving(const struct device *dev);
  */
 void lr11xx_set_rx_boost(const struct device *dev, bool enable);
 
+/**
+ * @brief Radio deaf time per duty-cycle wake transition, in microseconds
+ *
+ * Context restore + PLL lock plus the DTS-configured TCXO startup delay
+ * where fitted.  Used by the adapter (LoRaRadioBase) to size duty-cycle
+ * windows so the wake transition is charged against the preamble-catch
+ * budget — same accounting as the SX126x.
+ *
+ * @param dev LoRa device
+ * @return Transition deaf time in microseconds
+ */
+uint32_t lr11xx_get_wakeup_time_us(const struct device *dev);
+
 /**
  * @brief Get a random number from the radio
  *

zephcore/patches/zephyr-new/drivers/lora/lr20xx/lr20xx_lora.c

@@ -86,6 +86,13 @@ struct lr20xx_data {
 	bool rx_boost_enabled;
 	bool rx_boost_applied;
 
+	/* Stored duty-cycle timing from recv_duty_cycle() — re-arm paths
+	 * must reuse these exact values, never recompute: the window sizing
+	 * (detection budget, datasheet completion rule, wake transition) is
+	 * owned by the adapter layer. */
+	uint32_t dc_rx_ms;
+	uint32_t dc_sleep_ms;
+
 	/* CAD state */
 	lora_cad_cb cad_cb;
 	void *cad_user_data;
@@ -474,77 +481,28 @@ static void lr20xx_apply_modem_config(struct lr20xx_data *data,
 
 /* ── RX duty cycle ──────────────────────────────────────────────────── */
 
-/* Minimum preamble symbols needed for detection (same as SX126x) */
-#define LR20XX_DC_MIN_SYMBOLS_SF7_PLUS  8
-#define LR20XX_DC_MIN_SYMBOLS_SF6_LESS  12
-#define LR20XX_DC_TCXO_DELAY_US         1000
-
 /**
- * Compute duty cycle timing from current modem config and issue the
- * SetRxDutyCycle command.  Returns true on success, false if the
- * preamble is too short (falls back to continuous RX).
- *
- * Mirrors the SX126x symbol-based calculation: sleep through
- * (preamble_len - min_symbols - 2) symbols, wake for the remainder
- * plus margin.
+ * Re-issue the SetRxDutyCycle command with the timing stored by
+ * lr20xx_lora_recv_duty_cycle().  Returns true on success, false if no
+ * timing has been provided yet (falls back to continuous RX).
  */
 static bool lr20xx_apply_rx_duty_cycle(struct lr20xx_data *data)
 {
 	void *ctx = &data->hal_ctx;
-	struct lora_modem_config *mc = &data->modem_cfg;
 
-	uint8_t sf = (uint8_t)mc->datarate;
-	float bw_khz = bw_enum_to_khz(mc->bandwidth);
-	uint16_t preamble_len = mc->preamble_len;
-
-	uint16_t min_symbols = (sf >= 7) ? LR20XX_DC_MIN_SYMBOLS_SF7_PLUS
-					 : LR20XX_DC_MIN_SYMBOLS_SF6_LESS;
-
-	int16_t sleep_symbols = (int16_t)preamble_len - (int16_t)min_symbols;
-	if (sleep_symbols <= 0) {
-		LOG_WRN("Preamble too short for duty cycle "
-			"(need >%d symbols, have %d) — continuous RX",
-			min_symbols, preamble_len);
+	if (data->dc_rx_ms == 0 || data->dc_sleep_ms == 0) {
+		LOG_WRN("No duty-cycle timing stored — continuous RX");
 		data->rx_duty_cycle_enabled = false;
 		lr20xx_radio_common_set_rx_with_timeout_in_rtc_step(
 			ctx, 0xFFFFFF);
 		return false;
 	}
 
-	/* symbol_us = 2^SF / BW_kHz * 1000 */
-	uint32_t symbol_us = (uint32_t)((float)(1 << sf) * 1000.0f / bw_khz);
+	lr20xx_radio_common_set_rx_duty_cycle(ctx, data->dc_rx_ms,
+		data->dc_sleep_ms, LR20XX_RADIO_COMMON_RX_DUTY_CYCLE_MODE_RX);
 
-	/* Shave 2 symbols off sleep for timing margin */
-	int16_t sleep_symbols_safe = sleep_symbols - 2;
-	if (sleep_symbols_safe < 1) {
-		sleep_symbols_safe = 1;
-	}
-	uint32_t sleep_period_us = (uint16_t)sleep_symbols_safe * symbol_us;
-
-	uint32_t preamble_total_us = (preamble_len + 1) * symbol_us;
-	int32_t wake_calc1 = ((int32_t)preamble_total_us -
-			      ((int32_t)sleep_period_us -
-			       LR20XX_DC_TCXO_DELAY_US)) / 2;
-	uint32_t wake_calc2 = (min_symbols + 1) * symbol_us;
-
-	uint32_t wake_period_us =
-		(wake_calc1 > 0 && (uint32_t)wake_calc1 > wake_calc2)
-		? (uint32_t)wake_calc1 : wake_calc2;
-
-	uint32_t rx_ms  = (wake_period_us + 999) / 1000;  /* round up */
-	uint32_t slp_ms = (sleep_period_us + 999) / 1000;
-
-	if (rx_ms < 1) {
-		rx_ms = 1;
-	}
-	if (slp_ms < 1) {
-		slp_ms = 1;
-	}
-
-	lr20xx_radio_common_set_rx_duty_cycle(ctx, rx_ms, slp_ms,
-		LR20XX_RADIO_COMMON_RX_DUTY_CYCLE_MODE_RX);
-
-	LOG_DBG("RX duty cycle: SF%d rx=%ums sleep=%ums", sf, rx_ms, slp_ms);
+	LOG_DBG("RX duty cycle re-armed: rx=%ums sleep=%ums",
+		data->dc_rx_ms, data->dc_sleep_ms);
 	return true;
 }
 
@@ -1311,6 +1269,13 @@ static int lr20xx_lora_recv_duty_cycle(const struct device *dev,
 		return -EINVAL;
 	}
 
+	/* Explicit timing only — the adapter owns the window sizing. */
+	if (K_TIMEOUT_EQ(rx_period, K_FOREVER) ||
+	    K_TIMEOUT_EQ(sleep_period, K_FOREVER)) {
+		LOG_ERR("recv_duty_cycle: explicit rx/sleep periods required");
+		return -EINVAL;
+	}
+
 	k_mutex_lock(&data->spi_mutex, K_FOREVER);
 
 	data->async_rx_cb = cb;
@@ -1328,6 +1293,10 @@ static int lr20xx_lora_recv_duty_cycle(const struct device *dev,
 	if (rx_ms < 1) rx_ms = 1;
 	if (slp_ms < 1) slp_ms = 1;
 
+	/* Store for the re-arm paths (lr20xx_start_rx / lr20xx_restart_rx)
+	 * so every re-entry uses exactly this timing. */
+	data->dc_rx_ms = rx_ms;
+	data->dc_sleep_ms = slp_ms;
 	data->rx_duty_cycle_enabled = true;
 	lr20xx_radio_common_set_rx_duty_cycle(ctx, rx_ms, slp_ms,
 		LR20XX_RADIO_COMMON_RX_DUTY_CYCLE_MODE_RX);

zephcore/patches/zephyr-new/drivers/lora/native/sx126x/sx126x_ext.h

@@ -88,6 +88,20 @@ void sx126x_apply_heltec_reg_patch(const struct device *dev);
  */
 void sx126x_reset_agc(const struct device *dev);
 
+/**
+ * @brief Radio deaf time per duty-cycle wake transition, in microseconds
+ *
+ * Context save/restore + PLL lock (~1.5 ms) plus the DTS-configured TCXO
+ * startup delay where fitted.  Per datasheet rev 2.2 §13.1.7, the TCXO
+ * delay is inserted between the sleep and RX periods of every duty-cycle
+ * wake — it counts against the preamble-catch budget, outside both
+ * programmed periods.  Used by the adapter to size duty-cycle windows.
+ *
+ * @param dev LoRa device
+ * @return Transition deaf time in microseconds
+ */
+uint32_t sx126x_get_wakeup_time_us(const struct device *dev);
+
 /**
  * @brief Get duty-cycle preamble false-positive counter
  *

zephcore/patches/zephyr/0003-lora-sx126x-native.patch

@@ -68,7 +68,7 @@ index 17689720dd2..09982dc2e70 100644
  		return -EINVAL;
  	}
 diff --git a/drivers/lora/native/sx126x/sx126x.c b/drivers/lora/native/sx126x/sx126x.c
-index 30243ba5dc7..d2339ee8780 100644
+index 30243ba5dc7..69eefee6e0f 100644
 --- a/drivers/lora/native/sx126x/sx126x.c
 +++ b/drivers/lora/native/sx126x/sx126x.c
 @@ -6,14 +6,21 @@
@@ -173,21 +173,22 @@ index 30243ba5dc7..d2339ee8780 100644
  }
  
  static int sx126x_set_sync_word(const struct device *dev, bool public_network)
-@@ -247,6 +311,13 @@ static int sx126x_set_rx_gain(const struct device *dev, bool boosted)
+@@ -247,6 +311,14 @@ static int sx126x_set_rx_gain(const struct device *dev, bool boosted)
  {
  	uint8_t val = boosted ? SX126X_RX_GAIN_BOOSTED : SX126X_RX_GAIN_POWER_SAVING;
  
-+	/* Retention NOT used: without writing SX126X_REG_RX_GAIN_RETENTION_0,
-+	 * the chip resets 0x08AC to power-saving (0x94) on every SetRx command.
-+	 * This clears any residual AGC state accumulated during strong-signal
-+	 * reception (near-far problem: strong first relay locks AGC, weaker
-+	 * second relay missed).  sx126x_restart_rx() and hwStartReceive() both
-+	 * re-apply the desired gain after SetRx, after BUSY goes low and before
-+	 * any preamble can arrive (~3.4 ms RC startup window). */
++	/* Host-driven RX paths do not rely on retention: the chip resets
++	 * 0x08AC to power-saving (0x94) on every SetRx command, and
++	 * sx126x_restart_rx() / recv_async re-apply the desired gain right
++	 * after SetRx (after BUSY goes low, before any preamble can arrive).
++	 * Duty-cycle mode is different: its sleep->RX wakes are chip-internal
++	 * warm starts the host never sees, so the DC entry points
++	 * additionally pin 0x08AC into the warm-start retention list via
++	 * sx126x_retain_rx_gain() (DS sec 9.6: mandatory for SetRxDutyCycle). */
  	return sx126x_hal_write_regs(dev, SX126X_REG_RX_GAIN, &val, 1);
  }
  
-@@ -296,7 +367,7 @@ static int sx126x_get_packet_status(const struct device *dev,
+@@ -296,7 +368,7 @@ static int sx126x_get_packet_status(const struct device *dev,
  	uint8_t buf[3];
  	int ret;
  
@@ -196,7 +197,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	if (ret == 0) {
  		/* RSSI is -value/2 dBm */
  		*rssi = -((int16_t)buf[0] >> 1);
-@@ -367,6 +438,26 @@ static int sx126x_chip_init(const struct device *dev)
+@@ -367,6 +439,26 @@ static int sx126x_chip_init(const struct device *dev)
  		return ret;
  	}
  
@@ -223,7 +224,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	/* Set packet type to LoRa */
  	ret = sx126x_set_packet_type(dev, SX126X_PACKET_TYPE_LORA);
  	if (ret < 0) {
-@@ -374,10 +465,23 @@ static int sx126x_chip_init(const struct device *dev)
+@@ -374,10 +466,23 @@ static int sx126x_chip_init(const struct device *dev)
  		return ret;
  	}
  
@@ -250,7 +251,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	if (ret < 0) {
  		LOG_ERR("Set IRQ params failed: %d", ret);
  		return ret;
-@@ -398,7 +502,7 @@ static void sx126x_dio1_callback(const struct device *dev)
+@@ -398,7 +503,7 @@ static void sx126x_dio1_callback(const struct device *dev)
  {
  	struct sx126x_data *data = dev->data;
  
@@ -259,7 +260,7 @@ index 30243ba5dc7..d2339ee8780 100644
  }
  
  static void sx126x_set_rf_path(const struct device *dev, bool enable, bool tx)
-@@ -406,7 +510,20 @@ static void sx126x_set_rf_path(const struct device *dev, bool enable, bool tx)
+@@ -406,7 +511,20 @@ static void sx126x_set_rf_path(const struct device *dev, bool enable, bool tx)
  	const struct sx126x_hal_config *config = dev->config;
  
  	sx126x_hal_set_antenna_enable(dev, enable);
@@ -281,10 +282,44 @@ index 30243ba5dc7..d2339ee8780 100644
  		sx126x_hal_set_rf_switch(dev, enable, tx);
  	}
  }
-@@ -455,6 +572,98 @@ static int sx126x_reconnect_rf_gpios(const struct device *dev)
+@@ -455,6 +573,215 @@ static int sx126x_reconnect_rf_gpios(const struct device *dev)
  }
  #endif /* CONFIG_PM_DEVICE */
  
++/* -- Duty-cycle support helpers -- */
++
++/* Watchdog sampling period.  Must exceed the longest legitimate
++ * preamble-detect -> header gap at any supported preset so that two
++ * consecutive parked sightings can never be one real packet (worst
++ * case SF12/BW62.5, 16-sym preamble: ~1.9 s). */
++#define SX126X_DC_WATCHDOG_MS 3000
++
++/* DS sec 9.6: the RX gain register (0x08AC) is not part of the warm-start
++ * retention memory.  RxDutyCycle sleep->RX wakes are chip-internal warm
++ * starts -- without adding 0x08AC to the retention list, every window
++ * after the first sleep reverts to power-saving gain (-3 dB sensitivity)
++ * with no way for the host to intervene.  The datasheet calls this
++ * "mandatory when using the SetRxDutyCycle method, to keep on using the
++ * Rx Boosted gain".  Layout: entry count, then big-endian register
++ * address per entry. */
++static void sx126x_retain_rx_gain(const struct device *dev)
++{
++	uint8_t retention[3] = { 0x01, 0x08, 0xAC };
++
++	sx126x_hal_write_regs(dev, SX126X_REG_RX_GAIN_RETENTION_0,
++			      retention, 3);
++}
++
++/* (Re)arm the parked-RX watchdog and forget any parked evidence -- called
++ * from every duty-cycle (re)start site, which all bulk-clear the IRQ
++ * register first. */
++static void sx126x_dc_watchdog_kick(struct sx126x_data *data)
++{
++	data->dc_watchdog_strikes = 0;
++	k_work_reschedule_for_queue(&data->dio1_wq, &data->dc_watchdog_work,
++				    K_MSEC(SX126X_DC_WATCHDOG_MS));
++}
++
 +/* -- Lightweight RX restart -- */
 +
 +/* Restart RX as fast as possible -- used for RX->RX transitions in the
@@ -341,12 +376,20 @@ index 30243ba5dc7..d2339ee8780 100644
 +		sx126x_hal_write_cmd(dev, SX126X_CMD_STOP_TIMER_ON_PREAMBLE,
 +				     &stop_on_preamble, 1);
 +
++		/* Keep boosted RX gain alive across the chip-internal
++		 * sleep->RX wakes (DS sec 9.6, mandatory for DC mode).
++		 * Re-issued here as cheap insurance against Calibrate(ALL)
++		 * above disturbing the list. */
++		sx126x_retain_rx_gain(dev);
++
 +		/* Re-apply duty cycle with stored timing */
 +		uint8_t dc_buf[6];
 +		sys_put_be24(data->dc_rx_time, &dc_buf[0]);
 +		sys_put_be24(data->dc_sleep_time, &dc_buf[3]);
 +		sx126x_hal_write_cmd(dev, SX126X_CMD_SET_RX_DUTY_CYCLE,
 +				     dc_buf, 6);
++
++		sx126x_dc_watchdog_kick(data);
 +	} else {
 +		/* Non-DC continuous RX: plain SetRx(continuous), no symbol
 +		 * timer.  An earlier draft armed SetLoRaSymbNumTimeout here for
@@ -376,11 +419,86 @@ index 30243ba5dc7..d2339ee8780 100644
 +	sx126x_hal_write_regs(dev, SX126X_REG_RX_GAIN, &gain, 1);
 +	return 0;
 +}
++
++/* Parked-RX watchdog (see struct field comment).  Runs on the dedicated
++ * DIO1 work queue so it serialises with the IRQ handler and restart
++ * paths.  Self-terminating: returns without re-arming when duty-cycle RX
++ * is no longer active -- every DC (re)start kicks it again. */
++static void sx126x_dc_watchdog_handler(struct k_work *work)
++{
++	struct k_work_delayable *dwork = k_work_delayable_from_work(work);
++	struct sx126x_data *data = CONTAINER_OF(dwork, struct sx126x_data,
++						dc_watchdog_work);
++	const struct device *dev = data->dev;
++	uint16_t irq_status = 0;
++	bool parked = false;
++
++	if (!data->rx_duty_cycle_enabled ||
++	    atomic_get(&data->state) != SX126X_STATE_RX) {
++		return;
++	}
++
++	/* Legit packet mid-decode (HEADER_VALID latched): check again later. */
++	if (data->rx_packet_active) {
++		data->dc_watchdog_strikes = 0;
++		goto rearm;
++	}
++
++	/* BUSY high = duty-cycle sleep phase = cycling normally. */
++	if (sx126x_hal_is_busy(dev)) {
++		data->dc_watchdog_strikes = 0;
++		goto rearm;
++	}
++
++	if (k_mutex_lock(&data->lock, K_NO_WAIT) != 0) {
++		/* Another operation owns the chip right now -- not parked. */
++		data->dc_watchdog_strikes = 0;
++		goto rearm;
++	}
++
++	/* Re-check BUSY under the lock (same pattern as get_rssi_inst): a
++	 * sleep transition between the check above and the SPI read below
++	 * would stall the HAL and force-wake the chip. */
++	if (!sx126x_hal_is_busy(dev) &&
++	    sx126x_get_irq_status(dev, &irq_status) == 0) {
++		parked = (irq_status & SX126X_IRQ_PREAMBLE_DETECTED) &&
++			 !(irq_status & SX126X_IRQ_HEADER_VALID);
++	}
++
++	if (!parked) {
++		data->dc_watchdog_strikes = 0;
++		k_mutex_unlock(&data->lock);
++		goto rearm;
++	}
++
++	if (++data->dc_watchdog_strikes < 2) {
++		/* First sighting: could be a real preamble whose header is
++		 * still in flight.  A second sighting one full period later
++		 * cannot be the same packet (period > worst-case
++		 * preamble + sync + header airtime). */
++		k_mutex_unlock(&data->lock);
++		goto rearm;
++	}
++
++	/* Two strikes: a false preamble detect parked the chip in full RX
++	 * (StopTimerOnPreamble behaviour, AN1200.36 sec 3).  Nothing was
++	 * lost -- parked RX still receives -- but the duty cycle stopped.
++	 * Re-arm it.  Shares the dc_timeout_restarts stat: both paths mean
++	 * "false preamble cost extra RX-on time". */
++	atomic_inc(&data->dc_timeout_restarts);
++	(void)sx126x_restart_rx(dev, data);
++	k_mutex_unlock(&data->lock);
++	return; /* restart_rx re-kicked the watchdog */
++
++rearm:
++	k_work_schedule_for_queue(&data->dio1_wq, &data->dc_watchdog_work,
++				  K_MSEC(SX126X_DC_WATCHDOG_MS));
++}
 +
  static int sx126x_set_sleep(const struct device *dev)
  {
  	struct sx126x_data *data = dev->data;
-@@ -533,8 +742,16 @@ static void sx126x_handle_irq_rx_done(const struct device *dev, uint16_t irq_sta
+@@ -533,8 +860,16 @@ static void sx126x_handle_irq_rx_done(const struct device *dev, uint16_t irq_sta
  	struct sx126x_data *data = dev->data;
  	struct sx126x_rx_result result = { 0 };
  	uint8_t payload_len = 0, offset = 0;
@@ -397,7 +515,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	/* Get received packet info */
  	ret = sx126x_get_rx_buffer_status(dev, &payload_len, &offset);
  	if (ret < 0) {
-@@ -544,9 +761,26 @@ static void sx126x_handle_irq_rx_done(const struct device *dev, uint16_t irq_sta
+@@ -544,9 +879,26 @@ static void sx126x_handle_irq_rx_done(const struct device *dev, uint16_t irq_sta
  		/* Get signal quality */
  		sx126x_get_packet_status(dev, &result.rssi, &result.snr);
  
@@ -427,7 +545,7 @@ index 30243ba5dc7..d2339ee8780 100644
  			result.status = -EIO;
  		} else {
  			/* Read payload into shared buffer */
-@@ -564,20 +798,34 @@ static void sx126x_handle_irq_rx_done(const struct device *dev, uint16_t irq_sta
+@@ -564,20 +916,34 @@ static void sx126x_handle_irq_rx_done(const struct device *dev, uint16_t irq_sta
  		}
  	}
  
@@ -474,7 +592,7 @@ index 30243ba5dc7..d2339ee8780 100644
  		}
  	} else {
  		/* Sync mode */
-@@ -589,8 +837,69 @@ static void sx126x_handle_irq_rx_done(const struct device *dev, uint16_t irq_sta
+@@ -589,8 +955,69 @@ static void sx126x_handle_irq_rx_done(const struct device *dev, uint16_t irq_sta
  static void sx126x_handle_irq_timeout(const struct device *dev)
  {
  	struct sx126x_data *data = dev->data;
@@ -544,7 +662,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	sx126x_set_sleep(dev);
  
  	if (data->tx_async_signal != NULL) {
-@@ -633,10 +942,46 @@ static void sx126x_irq_work_handler(struct k_work *work)
+@@ -633,10 +1060,46 @@ static void sx126x_irq_work_handler(struct k_work *work)
  		sx126x_handle_irq_rx_done(dev, irq_status);
  	}
  
@@ -591,7 +709,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	/* Re-enable the DIO1 interrupt for the next event (unless sleeping) */
  	if (atomic_get(&data->state) != SX126X_REST_STATE) {
  		sx126x_hal_dio1_irq_enable(dev);
-@@ -682,7 +1027,7 @@ static int sx126x_lora_config(const struct device *dev,
+@@ -682,7 +1145,7 @@ static int sx126x_lora_config(const struct device *dev,
  	/* Configure PA and TX power based on chip variant and frequency */
  	ret = sx126x_hal_configure_tx_params(dev, config->tx_power,
  						config->frequency,
@@ -600,7 +718,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	if (ret < 0) {
  		goto out;
  	}
-@@ -698,6 +1043,29 @@ static int sx126x_lora_config(const struct device *dev,
+@@ -698,6 +1161,29 @@ static int sx126x_lora_config(const struct device *dev,
  		goto out;
  	}
  
@@ -630,7 +748,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	/* Set sync word */
  	ret = sx126x_set_sync_word(dev, config->public_network);
  	if (ret < 0) {
-@@ -721,6 +1089,8 @@ out:
+@@ -721,6 +1207,8 @@ out:
  	return ret;
  }
  
@@ -639,7 +757,7 @@ index 30243ba5dc7..d2339ee8780 100644
  static int sx126x_lora_send_async(const struct device *dev,
  				  uint8_t *data_buf, uint32_t data_len,
  				  struct k_poll_signal *async)
-@@ -738,11 +1108,27 @@ static int sx126x_lora_send_async(const struct device *dev,
+@@ -738,11 +1226,27 @@ static int sx126x_lora_send_async(const struct device *dev,
  		return -EINVAL;
  	}
  
@@ -669,7 +787,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	k_mutex_lock(&data->lock, K_FOREVER);
  
  	ret = sx126x_ensure_ready(dev);
-@@ -752,6 +1138,58 @@ static int sx126x_lora_send_async(const struct device *dev,
+@@ -752,6 +1256,58 @@ static int sx126x_lora_send_async(const struct device *dev,
  		return ret;
  	}
  
@@ -728,7 +846,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	data->tx_async_signal = async;
  	k_msgq_purge(&data->tx_msgq);
  
-@@ -777,6 +1215,29 @@ static int sx126x_lora_send_async(const struct device *dev,
+@@ -777,6 +1333,29 @@ static int sx126x_lora_send_async(const struct device *dev,
  	/* Enable antenna and set TX path */
  	sx126x_set_rf_path(dev, true, true);
  
@@ -758,7 +876,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	/* Start transmission with 10 second timeout */
  	ret = sx126x_set_tx(dev, 10000);
  	if (ret < 0) {
-@@ -847,6 +1308,8 @@ static int sx126x_lora_recv(const struct device *dev, uint8_t *data_buf,
+@@ -847,6 +1426,8 @@ static int sx126x_lora_recv(const struct device *dev, uint8_t *data_buf,
  	}
  
  	data->rx_cb = NULL;
@@ -767,7 +885,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	k_msgq_purge(&data->rx_msgq);
  
  	/* Set packet parameters for variable length reception */
-@@ -918,6 +1381,8 @@ static int sx126x_lora_recv_async(const struct device *dev,
+@@ -918,6 +1499,8 @@ static int sx126x_lora_recv_async(const struct device *dev,
  		/* Stop async reception */
  		data->rx_cb = NULL;
  		data->rx_cb_user_data = NULL;
@@ -776,7 +894,7 @@ index 30243ba5dc7..d2339ee8780 100644
  		if (atomic_cas(&data->state, SX126X_STATE_RX, SX126X_STATE_IDLE)) {
  			sx126x_set_standby(dev, SX126X_STANDBY_RC);
  			sx126x_set_sleep(dev);
-@@ -932,6 +1397,19 @@ static int sx126x_lora_recv_async(const struct device *dev,
+@@ -932,6 +1515,19 @@ static int sx126x_lora_recv_async(const struct device *dev,
  		return -EINVAL;
  	}
  
@@ -796,7 +914,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	if (!atomic_cas(&data->state, SX126X_REST_STATE, SX126X_STATE_RX)) {
  		LOG_ERR("Busy");
  		k_mutex_unlock(&data->lock);
-@@ -945,8 +1423,18 @@ static int sx126x_lora_recv_async(const struct device *dev,
+@@ -945,8 +1541,18 @@ static int sx126x_lora_recv_async(const struct device *dev,
  		return ret;
  	}
  
@@ -815,7 +933,7 @@ index 30243ba5dc7..d2339ee8780 100644
  
  	/* Set packet parameters */
  	ret = sx126x_set_packet_params(dev,
-@@ -959,6 +1447,7 @@ static int sx126x_lora_recv_async(const struct device *dev,
+@@ -959,6 +1565,7 @@ static int sx126x_lora_recv_async(const struct device *dev,
  				       SX126X_LORA_IQ_INVERTED : SX126X_LORA_IQ_STANDARD);
  	if (ret < 0) {
  		data->rx_cb = NULL;
@@ -823,7 +941,7 @@ index 30243ba5dc7..d2339ee8780 100644
  		sx126x_set_sleep(dev);
  		k_mutex_unlock(&data->lock);
  		return ret;
-@@ -971,11 +1460,21 @@ static int sx126x_lora_recv_async(const struct device *dev,
+@@ -971,11 +1578,21 @@ static int sx126x_lora_recv_async(const struct device *dev,
  	ret = sx126x_set_rx(dev, 0);
  	if (ret < 0) {
  		data->rx_cb = NULL;
@@ -845,7 +963,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	k_mutex_unlock(&data->lock);
  	return 0;
  }
-@@ -1051,7 +1550,7 @@ static int sx126x_lora_test_cw(const struct device *dev, uint32_t frequency,
+@@ -1051,7 +1668,7 @@ static int sx126x_lora_test_cw(const struct device *dev, uint32_t frequency,
  
  	/* Set PA config and TX power */
  	ret = sx126x_hal_configure_tx_params(dev, tx_power, frequency,
@@ -854,7 +972,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	if (ret < 0) {
  		sx126x_set_sleep(dev);
  		k_mutex_unlock(&data->lock);
-@@ -1083,14 +1582,602 @@ static int sx126x_lora_test_cw(const struct device *dev, uint32_t frequency,
+@@ -1083,14 +1700,595 @@ static int sx126x_lora_test_cw(const struct device *dev, uint32_t frequency,
  	return 0;
  }
  
@@ -1053,6 +1171,23 @@ index 30243ba5dc7..d2339ee8780 100644
 +	atomic_set(&data->dc_timeout_restarts, 0);
 +}
 +
++uint32_t sx126x_get_wakeup_time_us(const struct device *dev)
++{
++	const struct sx126x_hal_config *config = dev->config;
++	/* Context restore + PLL lock: "around 1 ms" per DS fig 13-2 ("not
++	 * accurate and may vary"), plus 500 us margin for the save side. */
++	uint32_t us = 1500;
++
++	/* DS rev 2.2 sec 13.1.7 note: with a chip-controlled TCXO, the
++	 * programmed startup delay is inserted between the sleep and RX
++	 * periods of every duty-cycle wake -- pure deaf time, outside both
++	 * programmed periods. */
++	if (config->dio3_tcxo_enable) {
++		us += config->tcxo_startup_delay_ms * 1000U;
++	}
++	return us;
++}
++
 +void sx126x_apply_heltec_reg_patch(const struct device *dev)
 +{
 +	struct sx126x_data *data = dev->data;
@@ -1360,55 +1495,25 @@ index 30243ba5dc7..d2339ee8780 100644
 +
 +	uint32_t rx_time, sleep_time;
 +
++	/* Explicit timing only.  The window sizing (detection budget,
++	 * datasheet Tpreamble+Theader <= 2*rxPeriod+sleepPeriod rule, TCXO
++	 * transition accounting) is owned by the caller -- the adapter layer
++	 * knows the mesh preamble policy, the driver just programs periods. */
 +	if (K_TIMEOUT_EQ(rx_period, K_FOREVER) ||
 +	    K_TIMEOUT_EQ(sleep_period, K_FOREVER)) {
-+		/* Auto-compute from modem config (RadioLib algorithm) */
-+		struct lora_modem_config *mc = &data->config;
-+		uint8_t sf = (uint8_t)mc->datarate;
-+		uint32_t bw_hz = bandwidth_to_hz(mc->bandwidth);
-+		float bw_khz = (float)bw_hz / 1000.0f;
-+		uint16_t preamble_len = mc->preamble_len;
-+
-+		uint16_t min_symbols = (sf >= 7) ? 8 : 12;
-+		int16_t sleep_symbols = (int16_t)preamble_len -
-+					(int16_t)min_symbols;
-+		if (sleep_symbols <= 0) {
-+			LOG_WRN("Preamble too short for duty cycle "
-+				"(need >%d, have %d)",
-+				min_symbols, preamble_len);
-+			data->rx_cb = NULL;
-+			atomic_inc(&data->rx_cb_gen);
-+			sx126x_set_sleep(dev);
-+			k_mutex_unlock(&data->lock);
-+			atomic_set(&data->state, SX126X_REST_STATE);
-+			return -EINVAL;
-+		}
-+
-+		uint32_t symbol_us = (uint32_t)((float)(1 << sf) *
-+						 1000.0f / bw_khz);
-+
-+		int16_t sleep_symbols_safe = sleep_symbols - 2;
-+		if (sleep_symbols_safe < 1) sleep_symbols_safe = 1;
-+		uint32_t sleep_us = (uint16_t)sleep_symbols_safe * symbol_us;
-+
-+		uint32_t preamble_us = (preamble_len + 1) * symbol_us;
-+		int32_t wake1 = ((int32_t)preamble_us -
-+				 ((int32_t)sleep_us - 1000)) / 2;
-+		uint32_t wake2 = (min_symbols + 1) * symbol_us;
-+		uint32_t rx_us = (wake1 > 0 && (uint32_t)wake1 > wake2)
-+				  ? (uint32_t)wake1 : wake2;
-+
-+		/* Convert us to 15.625us steps */
-+		rx_time = (rx_us * 64) / 1000;
-+		sleep_time = (sleep_us * 64) / 1000;
-+	} else {
-+		/* Explicit timing from caller */
-+		uint32_t rx_us = k_ticks_to_us_ceil32(rx_period.ticks);
-+		uint32_t slp_us = k_ticks_to_us_ceil32(sleep_period.ticks);
-+		rx_time = (rx_us * 64) / 1000;
-+		sleep_time = (slp_us * 64) / 1000;
++		LOG_ERR("recv_duty_cycle: explicit rx/sleep periods required");
++		data->rx_cb = NULL;
++		atomic_inc(&data->rx_cb_gen);
++		sx126x_set_sleep(dev);
++		k_mutex_unlock(&data->lock);
++		atomic_set(&data->state, SX126X_REST_STATE);
++		return -EINVAL;
 +	}
 +
++	/* Convert us to 15.625us steps */
++	rx_time = (k_ticks_to_us_ceil32(rx_period.ticks) * 64) / 1000;
++	sleep_time = (k_ticks_to_us_ceil32(sleep_period.ticks) * 64) / 1000;
++
 +	if (rx_time < 64) rx_time = 64;
 +	if (sleep_time < 64) sleep_time = 64;
 +
@@ -1425,16 +1530,22 @@ index 30243ba5dc7..d2339ee8780 100644
 +	sx126x_hal_write_cmd(dev, SX126X_CMD_STOP_TIMER_ON_PREAMBLE,
 +			     &stop_on_preamble, 1);
 +
++	/* Apply RX gain, then pin it into the warm-start retention list so the
++	 * chip-internal sleep->RX wakes restore it (DS sec 9.6: mandatory for
++	 * SetRxDutyCycle -- without this every window after the first sleep
++	 * listens at power-saving gain, a silent -3 dB sensitivity loss). */
++	uint8_t gain = data->rx_boost_enabled ? SX126X_RX_GAIN_BOOSTED
++					      : SX126X_RX_GAIN_POWER_SAVING;
++	sx126x_hal_write_regs(dev, SX126X_REG_RX_GAIN, &gain, 1);
++	sx126x_retain_rx_gain(dev);
++
 +	uint8_t buf[6];
 +
 +	sys_put_be24(rx_time, &buf[0]);
 +	sys_put_be24(sleep_time, &buf[3]);
 +	sx126x_hal_write_cmd(dev, SX126X_CMD_SET_RX_DUTY_CYCLE, buf, 6);
 +
-+	/* Apply RX gain */
-+	uint8_t gain = data->rx_boost_enabled ? SX126X_RX_GAIN_BOOSTED
-+					      : SX126X_RX_GAIN_POWER_SAVING;
-+	sx126x_hal_write_regs(dev, SX126X_REG_RX_GAIN, &gain, 1);
++	sx126x_dc_watchdog_kick(data);
 +
 +	k_mutex_unlock(&data->lock);
 +
@@ -1464,7 +1575,7 @@ index 30243ba5dc7..d2339ee8780 100644
  };
  
  #ifdef CONFIG_PM_DEVICE
-@@ -1112,6 +2199,7 @@ static int sx126x_pm_action(const struct device *dev,
+@@ -1112,6 +2310,7 @@ static int sx126x_pm_action(const struct device *dev,
  static int sx126x_init(const struct device *dev)
  {
  	struct sx126x_data *data = dev->data;
@@ -1472,7 +1583,7 @@ index 30243ba5dc7..d2339ee8780 100644
  	int ret;
  
  	/* Initialize data structures */
-@@ -1121,9 +2209,26 @@ static int sx126x_init(const struct device *dev)
+@@ -1121,9 +2320,29 @@ static int sx126x_init(const struct device *dev)
  	k_msgq_init(&data->rx_msgq, (char *)&data->rx_result,
  		    sizeof(struct sx126x_rx_result), 1);
  	k_work_init(&data->irq_work, sx126x_irq_work_handler);
@@ -1490,6 +1601,9 @@ index 30243ba5dc7..d2339ee8780 100644
 +	 * sx126x_set_rx_boost() extension API. */
 +	data->rx_boost_enabled = config->rx_boosted;
 +	atomic_set(&data->dc_timeout_restarts, 0);
++	k_work_init_delayable(&data->dc_watchdog_work,
++			      sx126x_dc_watchdog_handler);
++	data->dc_watchdog_strikes = 0;
 +
 +	/* Start dedicated DIO1 work queue */
 +	k_work_queue_start(&data->dio1_wq, sx126x_dio1_wq_stack,
@@ -1500,10 +1614,10 @@ index 30243ba5dc7..d2339ee8780 100644
  	/* Initialize HAL */
  	ret = sx126x_hal_init(dev);
 diff --git a/drivers/lora/native/sx126x/sx126x.h b/drivers/lora/native/sx126x/sx126x.h
-index 9dbf3f26586..880b3240d22 100644
+index 9dbf3f26586..2598b56d048 100644
 --- a/drivers/lora/native/sx126x/sx126x.h
 +++ b/drivers/lora/native/sx126x/sx126x.h
-@@ -56,13 +56,58 @@ struct sx126x_data {
+@@ -56,13 +56,69 @@ struct sx126x_data {
  	/* Async RX callback */
  	lora_recv_cb rx_cb;
  	void *rx_cb_user_data;
@@ -1545,6 +1659,17 @@ index 9dbf3f26586..880b3240d22 100644
 +	uint32_t dc_rx_time;    /* stored duty cycle rx period (15.625us steps) */
 +	uint32_t dc_sleep_time; /* stored duty cycle sleep period (15.625us steps) */
 +
++	/* Parked-RX watchdog.  StopTimerOnPreamble=1 means a false preamble
++	 * detect parks the chip in full RX "until the next received frame"
++	 * (AN1200.36 sec 3) with no IRQ fired -- nothing is lost (parked RX
++	 * still receives) but duty cycling silently stops costing full RX
++	 * current.  The watchdog samples the IRQ register every few seconds
++	 * and re-arms the duty cycle after two consecutive sightings of
++	 * PREAMBLE_DETECTED without HEADER_VALID (one packet can never span
++	 * two sightings; restart sites and terminal IRQs clear the bit). */
++	struct k_work_delayable dc_watchdog_work;
++	uint8_t dc_watchdog_strikes;
++
 +	/* Duty-cycle preamble false-positive counter: incremented whenever
 +	 * IRQ_RX_TX_TIMEOUT fires during duty-cycle RX (preamble detector
 +	 * tripped but no valid sync/header followed -- re-arm triggered).