Add 60s watchdog for nrf52

In order to restore after battery voltage sags too low

examples/companion_radio/main.cpp

@@ -223,6 +223,7 @@ void setup() {
 }
 
 void loop() {
+  board.loop();
   the_mesh.loop();
   sensors.loop();
 #ifdef DISPLAY_CLASS

examples/kiss_modem/main.cpp

@@ -119,6 +119,7 @@ void setup() {
 }
 
 void loop() {
+  board.loop();
   modem->loop();
 
   if (!modem->isActuallyTransmitting()) {

examples/simple_repeater/main.cpp

@@ -106,6 +106,8 @@ void setup() {
 }
 
 void loop() {
+  board.loop();
+
   int len = strlen(command);
   while (Serial.available() && len < sizeof(command)-1) {
     char c = Serial.read();

examples/simple_room_server/main.cpp

@@ -83,6 +83,8 @@ void setup() {
 }
 
 void loop() {
+  board.loop();
+
   int len = strlen(command);
   while (Serial.available() && len < sizeof(command)-1) {
     char c = Serial.read();

examples/simple_secure_chat/main.cpp

@@ -589,6 +589,7 @@ void setup() {
 }
 
 void loop() {
+  board.loop();
   the_mesh.loop();
   rtc_clock.tick();
 }

examples/simple_sensor/main.cpp

@@ -117,6 +117,8 @@ void setup() {
 }
 
 void loop() {
+  board.loop();
+
   int len = strlen(command);
   while (Serial.available() && len < sizeof(command)-1) {
     char c = Serial.read();

src/MeshCore.h

@@ -58,6 +58,7 @@ public:
   virtual uint8_t getStartupReason() const = 0;
   virtual bool getBootloaderVersion(char* version, size_t max_len) { return false; }
   virtual bool startOTAUpdate(const char* id, char reply[]) { return false; }   // not supported
+  virtual void loop() { /* no op */ }
 
   // Power management interface (boards with power management override these)
   virtual bool isExternalPowered() { return false; }

src/helpers/NRF52Board.cpp

@@ -112,15 +112,29 @@ const char* NRF52Board::getShutdownReasonString(uint8_t reason) {
 bool NRF52Board::checkBootVoltage(const PowerMgtConfig* config) {
   initPowerMgr();
 
+  // Store config for runtime use (voltage monitoring, WDT)
+  _power_config = config;
+  _last_voltage_check_ms = 0;
+  _low_voltage_count = 0;
+
   // Read boot voltage
   boot_voltage_mv = getBattMilliVolts();
-  
-  if (config->voltage_bootlock == 0) return true;  // Protection disabled
+
+  if (config->voltage_bootlock == 0) {
+    // Boot protection disabled, but still init WDT if configured
+    if (config->wdt_timeout_ms > 0) {
+      initWatchdog(config->wdt_timeout_ms);
+    }
+    return true;
+  }
 
   // Skip check if externally powered
   if (isExternalPowered()) {
     MESH_DEBUG_PRINTLN("PWRMGT: Boot check skipped (external power)");
     boot_voltage_mv = getBattMilliVolts();
+    if (config->wdt_timeout_ms > 0) {
+      initWatchdog(config->wdt_timeout_ms);
+    }
     return true;
   }
 
@@ -136,6 +150,11 @@ bool NRF52Board::checkBootVoltage(const PowerMgtConfig* config) {
     return false;  // Should never reach this
   }
 
+  // Boot voltage OK — start WDT if configured
+  if (config->wdt_timeout_ms > 0) {
+    initWatchdog(config->wdt_timeout_ms);
+  }
+
   return true;
 }
 
@@ -236,8 +255,67 @@ void NRF52Board::configureVoltageWake(uint8_t ain_channel, uint8_t refsel) {
 
   MESH_DEBUG_PRINTLN("PWRMGT: VBUS wake configured");
 }
+
+#define VOLTAGE_CHECK_INTERVAL_MS  30000
+#define LOW_VOLTAGE_COUNT_THRESHOLD  3
+
+void NRF52Board::initWatchdog(uint32_t timeout_ms) {
+  // Configure WDT via direct register access (same pattern as LPCOMP/POWER registers)
+  NRF_WDT->CONFIG = WDT_CONFIG_SLEEP_Run << WDT_CONFIG_SLEEP_Pos;  // Keep running during WFE sleep
+  NRF_WDT->CRV = (uint32_t)((uint64_t)timeout_ms * 32768 / 1000);  // Timeout in 32.768kHz ticks
+  NRF_WDT->RREN = WDT_RREN_RR0_Enabled << WDT_RREN_RR0_Pos;  // Enable reload register 0
+  NRF_WDT->TASKS_START = 1;  // Start — cannot be stopped once started
+
+  // Initial feed
+  NRF_WDT->RR[0] = WDT_RR_RR_Reload;
+
+  MESH_DEBUG_PRINTLN("PWRMGT: WDT started (%lu ms)", (unsigned long)timeout_ms);
+}
+
+void NRF52Board::feedWatchdog() {
+  if (NRF_WDT->RUNSTATUS) {
+    NRF_WDT->RR[0] = WDT_RR_RR_Reload;
+  }
+}
+
+void NRF52Board::checkRuntimeVoltage() {
+  if (_power_config == nullptr || _power_config->voltage_runtime == 0) return;
+
+  uint32_t now = millis();
+  if (now - _last_voltage_check_ms < VOLTAGE_CHECK_INTERVAL_MS) return;
+  _last_voltage_check_ms = now;
+
+  if (isExternalPowered()) {
+    _low_voltage_count = 0;
+    return;
+  }
+
+  uint16_t mv = getBattMilliVolts();
+
+  // Ignore ADC glitch readings
+  if (mv < 1000) return;
+
+  if (mv < _power_config->voltage_runtime) {
+    _low_voltage_count++;
+    MESH_DEBUG_PRINTLN("PWRMGT: Low voltage %u mV (%u/%u)",
+        mv, _low_voltage_count, LOW_VOLTAGE_COUNT_THRESHOLD);
+    if (_low_voltage_count >= LOW_VOLTAGE_COUNT_THRESHOLD) {
+      MESH_DEBUG_PRINTLN("PWRMGT: Runtime voltage too low - shutting down");
+      initiateShutdown(SHUTDOWN_REASON_LOW_VOLTAGE);
+    }
+  } else {
+    _low_voltage_count = 0;
+  }
+}
 #endif
 
+void NRF52Board::loop() {
+#ifdef NRF52_POWER_MANAGEMENT
+  feedWatchdog();
+  checkRuntimeVoltage();
+#endif
+}
+
 void NRF52BoardDCDC::begin() {
   NRF52Board::begin();
 
@@ -252,10 +330,14 @@ void NRF52BoardDCDC::begin() {
 }
 
 void NRF52Board::sleep(uint32_t secs) {
+#ifdef NRF52_POWER_MANAGEMENT
+  feedWatchdog();
+#endif
+
   // Clear FPU interrupt flags to avoid insomnia
   // see errata 87 for details https://docs.nordicsemi.com/bundle/errata_nRF52840_Rev3/page/ERR/nRF52840/Rev3/latest/anomaly_840_87.html
   #if (__FPU_USED == 1)
-  __set_FPSCR(__get_FPSCR() & ~(0x0000009F)); 
+  __set_FPSCR(__get_FPSCR() & ~(0x0000009F));
   (void) __get_FPSCR();
   NVIC_ClearPendingIRQ(FPU_IRQn);
   #endif

src/helpers/NRF52Board.h

@@ -21,6 +21,11 @@ struct PowerMgtConfig {
   // Boot protection voltage threshold (millivolts)
   // Set to 0 to disable boot protection
   uint16_t voltage_bootlock;
+
+  // Runtime low voltage shutdown threshold (millivolts), 0=disabled
+  uint16_t voltage_runtime;
+  // Watchdog timer timeout (ms), 0=disabled
+  uint32_t wdt_timeout_ms;
 };
 #endif
 
@@ -38,14 +43,25 @@ protected:
   uint8_t shutdown_reason;            // GPREGRET value (why we entered last SYSTEMOFF)
   uint16_t boot_voltage_mv;           // Battery voltage at boot (millivolts)
 
+  const PowerMgtConfig* _power_config;
+  uint32_t _last_voltage_check_ms;
+  uint8_t _low_voltage_count;
+
   bool checkBootVoltage(const PowerMgtConfig* config);
   void enterSystemOff(uint8_t reason);
   void configureVoltageWake(uint8_t ain_channel, uint8_t refsel);
   virtual void initiateShutdown(uint8_t reason);
+  void initWatchdog(uint32_t timeout_ms);
+  void feedWatchdog();
+  void checkRuntimeVoltage();
 #endif
 
 public:
-  NRF52Board(char *otaname) : ota_name(otaname) {}
+  NRF52Board(char *otaname) : ota_name(otaname)
+#ifdef NRF52_POWER_MANAGEMENT
+    , _power_config(nullptr), _last_voltage_check_ms(0), _low_voltage_count(0)
+#endif
+  {}
   virtual void begin();
   virtual uint8_t getStartupReason() const override { return startup_reason; }
   virtual float getMCUTemperature() override;
@@ -53,6 +69,7 @@ public:
   virtual bool getBootloaderVersion(char* version, size_t max_len) override;
   virtual bool startOTAUpdate(const char *id, char reply[]) override;
   virtual void sleep(uint32_t secs) override;
+  virtual void loop() override;
 
 #ifdef NRF52_POWER_MANAGEMENT
   bool isExternalPowered() override;

variants/gat562_mesh_tracker_pro/GAT562MeshTrackerProBoard.cpp

@@ -10,7 +10,9 @@
 const PowerMgtConfig power_config = {
   .lpcomp_ain_channel = PWRMGT_LPCOMP_AIN,
   .lpcomp_refsel = PWRMGT_LPCOMP_REFSEL,
-  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK
+  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK,
+  .voltage_runtime = PWRMGT_VOLTAGE_BOOTLOCK - 200,
+  .wdt_timeout_ms = 60000
 };
 
 

variants/heltec_t114/T114Board.cpp

@@ -9,7 +9,9 @@
 const PowerMgtConfig power_config = {
   .lpcomp_ain_channel = PWRMGT_LPCOMP_AIN,
   .lpcomp_refsel = PWRMGT_LPCOMP_REFSEL,
-  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK
+  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK,
+  .voltage_runtime = PWRMGT_VOLTAGE_BOOTLOCK - 200,
+  .wdt_timeout_ms = 60000
 };
 
 void T114Board::initiateShutdown(uint8_t reason) {

variants/rak4631/RAK4631Board.cpp

@@ -9,7 +9,9 @@
 const PowerMgtConfig power_config = {
   .lpcomp_ain_channel = PWRMGT_LPCOMP_AIN,
   .lpcomp_refsel = PWRMGT_LPCOMP_REFSEL,
-  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK
+  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK,
+  .voltage_runtime = PWRMGT_VOLTAGE_BOOTLOCK - 200,
+  .wdt_timeout_ms = 60000
 };
 
 void RAK4631Board::initiateShutdown(uint8_t reason) {

variants/sensecap_solar/SenseCapSolarBoard.cpp

@@ -7,7 +7,9 @@
 const PowerMgtConfig power_config = {
   .lpcomp_ain_channel = PWRMGT_LPCOMP_AIN,
   .lpcomp_refsel = PWRMGT_LPCOMP_REFSEL,
-  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK
+  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK,
+  .voltage_runtime = PWRMGT_VOLTAGE_BOOTLOCK - 200,
+  .wdt_timeout_ms = 60000
 };
 
 void SenseCapSolarBoard::initiateShutdown(uint8_t reason) {

variants/xiao_nrf52/XiaoNrf52Board.cpp

@@ -11,7 +11,9 @@
 const PowerMgtConfig power_config = {
   .lpcomp_ain_channel = PWRMGT_LPCOMP_AIN,
   .lpcomp_refsel = PWRMGT_LPCOMP_REFSEL,
-  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK
+  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK,
+  .voltage_runtime = PWRMGT_VOLTAGE_BOOTLOCK - 200,
+  .wdt_timeout_ms = 60000
 };
 
 void XiaoNrf52Board::initiateShutdown(uint8_t reason) {