stm32wl: implement powersaving for repeaters

src/helpers/CommonCLI.cpp

@@ -442,7 +442,7 @@ void CommonCLI::handleCommand(uint32_t sender_timestamp, char* command, char* re
       _prefs->powersaving_enabled = 1;
       savePrefs();
       strcpy(reply, "on - Immediate effect");
-#elif defined(ESP32) && !defined(WITH_BRIDGE)
+#elif (defined(ESP32) || defined(STM32_PLATFORM)) && !defined(WITH_BRIDGE)
       _prefs->powersaving_enabled = 1;
       savePrefs();
       strcpy(reply, "on - After 2 minutes");

src/helpers/stm32/STM32Board.cpp

@@ -0,0 +1,146 @@
+#if defined(STM32_PLATFORM)
+#include "STM32Board.h"
+
+#if defined(STM32WLxx)
+#include <SubGhz.h>
+
+// Low-power sleep for the STM32WL. The core enters a Stop mode while the on-chip
+// radio keeps receiving, so either an incoming frame (through the radio's IRQ on
+// EXTI line 44) or a periodic RTC timer wakes it again. Stop mode halts SysTick,
+// so on wake millis() is advanced by the elapsed time read back from the RTC.
+
+extern "C" __IO uint32_t uwTick;            // the tick counter behind millis()
+extern "C" void SystemClock_Config(void);   // provided by the board variant
+
+static RTC_HandleTypeDef s_hrtc;
+static bool s_rtc_ready = false;
+
+// Acknowledge the wake-up timer interrupt; the weak default handler would trap.
+extern "C" void RTC_WKUP_IRQHandler(void) {
+  HAL_RTCEx_WakeUpTimerIRQHandler(&s_hrtc);
+}
+
+static bool stm32wl_rtc_begin() {
+  if (s_rtc_ready) return true;
+
+  HAL_PWR_EnableBkUpAccess();
+
+  __HAL_RCC_LSI_ENABLE();
+  while (__HAL_RCC_GET_FLAG(RCC_FLAG_LSIRDY) == RESET) { }
+
+  __HAL_RCC_RTC_CONFIG(RCC_RTCCLKSOURCE_LSI);
+  __HAL_RCC_RTCAPB_CLK_ENABLE();
+  __HAL_RCC_RTC_ENABLE();
+
+  s_hrtc.Instance = RTC;
+  s_hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
+  s_hrtc.Init.AsynchPrediv = 127;   // the LSI runs at ~32 kHz, so /128 gives 250 Hz
+  s_hrtc.Init.SynchPrediv = 249;    // and /250 yields a 1 Hz ck_spre
+  s_hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
+  s_hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
+  s_hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
+  s_hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_NONE;
+  if (HAL_RTC_Init(&s_hrtc) != HAL_OK) return false;
+
+  HAL_NVIC_SetPriority(RTC_WKUP_IRQn, 15, 0);
+  HAL_NVIC_EnableIRQ(RTC_WKUP_IRQn);
+
+  s_rtc_ready = true;
+  return true;
+}
+
+static void stm32wl_rtc_zero() {
+  RTC_TimeTypeDef t = {};
+  HAL_RTC_SetTime(&s_hrtc, &t, RTC_FORMAT_BIN);
+}
+
+static uint32_t stm32wl_rtc_elapsed_ms() {
+  RTC_TimeTypeDef t;
+  RTC_DateTypeDef d;
+  HAL_RTC_GetTime(&s_hrtc, &t, RTC_FORMAT_BIN);
+  // Reading the date is mandatory after the time: it releases the shadow registers
+  // that the time read locks.
+  HAL_RTC_GetDate(&s_hrtc, &d, RTC_FORMAT_BIN);
+
+  uint32_t ms = ((t.Hours * 60UL + t.Minutes) * 60UL + t.Seconds) * 1000UL;
+  if (t.SecondFraction) {
+    ms += ((t.SecondFraction - t.SubSeconds) * 1000UL) / (t.SecondFraction + 1);
+  }
+  return ms;
+}
+
+void STM32Board::sleep(uint32_t secs) {
+  // A frame that arrived since the last loop() should be handled, not slept through.
+  if (SubGhz.isInterruptPending()) return;
+
+  bool timed = (secs > 0) && stm32wl_rtc_begin();
+
+  // The radio's interrupt is wired to EXTI line 44; unmasking it lets an incoming
+  // frame wake the core from Stop.
+  LL_EXTI_EnableIT_32_63(LL_EXTI_LINE_44);
+
+  if (timed) {
+    stm32wl_rtc_zero();
+    HAL_RTCEx_SetWakeUpTimer_IT(&s_hrtc, secs - 1, RTC_WAKEUPCLOCK_CK_SPRE_16BITS, 0);
+  }
+
+  // Keep interrupts masked across the transition so that the waking ISR runs only
+  // after SystemClock_Config() has restored the clock, rather than at the slower
+  // MSI range that the core wakes into.
+  __disable_irq();
+
+  // Re-check now that interrupts are masked. Had a frame arrived during the setup
+  // above, its ISR would already have run and disabled the radio interrupt in the
+  // NVIC, and a disabled but pending interrupt cannot wake WFI. The request is still
+  // asserted on EXTI line 44, so bail out rather than sleep through it.
+  if (SubGhz.isInterruptPending()) {
+    if (timed) HAL_RTCEx_DeactivateWakeUpTimer(&s_hrtc);
+    __enable_irq();
+    return;
+  }
+
+  HAL_SuspendTick();
+
+  // For a node that stays in continuous RX, Stop0 is the lower-power choice even
+  // though it is the shallower sleep. Stop1, Stop2 and Standby force the SMPS into
+  // bypass, which drops the radio back onto the LDO, whereas Stop0 keeps the SMPS
+  // running and the radio on DC-DC. The radio it saves outweighs the slightly
+  // higher core current, so idle-RX firmware should build with STM32WL_SLEEP_STOP0.
+#if defined(STM32WL_SLEEP_STOP0)
+  HAL_PWREx_EnterSTOP0Mode(PWR_STOPENTRY_WFI);
+#else
+  HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFI);
+#endif
+
+  // A Stop mode always exits on the MSI clock, so restore the configured clock tree.
+  SystemClock_Config();
+  HAL_ResumeTick();
+
+  if (timed) {
+    HAL_RTCEx_DeactivateWakeUpTimer(&s_hrtc);
+    uwTick += stm32wl_rtc_elapsed_ms();
+  }
+
+  __enable_irq();
+}
+
+// Enable the SMPS step-down so that the core and on-chip radio draw from the DC-DC
+// regulator rather than the LDO, which roughly halves the radio's RX current. The
+// board must have the SMPS coil on VLXSMPS populated. Stop1, Stop2 and Standby force
+// the converter back to bypass, so the saving only applies in Run, LP-Run and Stop0.
+void STM32Board::lowPowerInit() {
+#if defined(STM32WL_ENABLE_SMPS)
+  SET_BIT(PWR->CR5, PWR_CR5_SMPSEN);
+#endif
+}
+
+#else  // other STM32 parts have no on-chip radio to wake on, so there is nothing to do
+
+void STM32Board::sleep(uint32_t secs) {
+  (void)secs;
+}
+
+void STM32Board::lowPowerInit() { }
+
+#endif  // STM32WLxx
+#endif  // STM32_PLATFORM

src/helpers/stm32/STM32Board.h

@@ -7,9 +7,14 @@ class STM32Board : public mesh::MainBoard {
 protected:
   uint8_t startup_reason;
 
+  // Performs one-time low-power configuration at boot (the SMPS on STM32WL); it is
+  // a no-op on other STM32 parts.
+  void lowPowerInit();
+
 public:
   virtual void begin() {
     startup_reason = BD_STARTUP_NORMAL;
+    lowPowerInit();
   }
 
   uint8_t getStartupReason() const override { return startup_reason; }
@@ -32,6 +37,9 @@ class STM32Board : public mesh::MainBoard {
     HAL_PWREx_EnterSHUTDOWNMode();
   }
 
+  // Low-power sleep until a LoRa frame arrives or 'secs' elapse (STM32WL only).
+  void sleep(uint32_t secs) override;
+
 #if defined(P_LORA_TX_LED)
   void onBeforeTransmit() override {
     digitalWrite(P_LORA_TX_LED, LOW);   // turn TX LED on

variants/rak3x72/platformio.ini

@@ -8,7 +8,9 @@ build_flags = ${stm32_base.build_flags}
   -D WRAPPER_CLASS=CustomSTM32WLxWrapper
   -D SPI_INTERFACES_COUNT=0
   -D RX_BOOSTED_GAIN=true
-;  -D STM32WL_TCXO_VOLTAGE=1.6 ; defaults to 0 if undef
+  -D STM32WL_ENABLE_SMPS ; run the radio from the SMPS/DC-DC regulator (needs the VLXSMPS coil)
+  -D STM32WL_SLEEP_STOP0 ; sleep in Stop0 so the SMPS stays active during continuous RX
+;  -D STM32WL_TCXO_VOLTAGE=1.8 ; override the auto-detected default from target.cpp
 ;  -D LORA_TX_POWER=14 ; Defaults to 22 for HP, 14 is for LP version
   -I variants/rak3x72
 build_src_filter = ${stm32_base.build_src_filter}

variants/rak3x72/target.cpp

@@ -24,9 +24,11 @@ SensorManager sensors;
   #define LORA_CR      5
 #endif
 
+// Auto-detect the oscillator. begin() is given a TCXO voltage; RadioLib falls
+// back to the crystal if it fails to start, so one build runs on both the
+// crystal RAK3172 and the TCXO -T. A hard-coded 0 leaves the -T failing (-707).
 #ifndef STM32WL_TCXO_VOLTAGE
-  // TCXO set to 0 for RAK3172
-  #define STM32WL_TCXO_VOLTAGE 0
+  #define STM32WL_TCXO_VOLTAGE 1.8
 #endif
 
 #ifndef LORA_TX_POWER