Service watchdog during bounded CAD

src/MeshCore.h

@@ -53,6 +53,10 @@ public:
   virtual void onAfterTransmit() { }
   virtual void reboot() = 0;
   virtual void powerOff() { /* no op */ }
+  // Reload an already-running system watchdog without enabling one. Long,
+  // internally bounded operations can use this while retaining their own
+  // timeout. Boards without an explicit watchdog need no implementation.
+  virtual void serviceWatchdog() { /* no op */ }
   // Called by example setup() functions to signal that boot is complete.
   // Boards may override to stop a boot-indicator LED sequence or similar.
   // Default no-op: boards that don't care need not implement anything.

src/helpers/NRF52Board.cpp

@@ -56,6 +56,19 @@ void NRF52Board::begin() {
   startup_reason = BD_STARTUP_NORMAL;
 }
 
+#if NRF52_WATCHDOG_TIMEOUT_SECONDS > 0
+static void reloadWatchdogChannels() {
+  // Ordinarily only RR0 is enabled. If a bootloader left the watchdog running
+  // with a different reload channel, service every enabled channel.
+  const uint32_t enabled_channels = NRF_WDT->RREN & 0xFFUL;
+  for (uint8_t channel = 0; channel < 8; channel++) {
+    if (enabled_channels & (1UL << channel)) {
+      NRF_WDT->RR[channel] = WDT_RR_RR_Reload;
+    }
+  }
+}
+#endif
+
 void NRF52Board::feedWatchdog(bool enabled) {
 #if NRF52_WATCHDOG_TIMEOUT_SECONDS > 0
   // The nRF52 watchdog cannot be stopped after it starts. When the persisted
@@ -77,20 +90,18 @@ void NRF52Board::feedWatchdog(bool enabled) {
     NRF_WDT->TASKS_START = 1;
   }
 
-  // Ordinarily only RR0 is enabled. If a bootloader left the watchdog running
-  // with a different reload channel, service every enabled channel rather
-  // than assuming ownership of RR0 and immediately entering a reset loop.
-  const uint32_t enabled_channels = NRF_WDT->RREN & 0xFFUL;
-  for (uint8_t channel = 0; channel < 8; channel++) {
-    if (enabled_channels & (1UL << channel)) {
-      NRF_WDT->RR[channel] = WDT_RR_RR_Reload;
-    }
-  }
+  reloadWatchdogChannels();
 #else
   (void)enabled;
 #endif
 }
 
+void NRF52Board::serviceWatchdog() {
+#if NRF52_WATCHDOG_TIMEOUT_SECONDS > 0
+  if (NRF_WDT->RUNSTATUS != 0) reloadWatchdogChannels();
+#endif
+}
+
 #ifdef NRF52_POWER_MANAGEMENT
 // Power Management global variables
 uint32_t g_nrf52_reset_reason = 0;     // Reset/Startup reason

src/helpers/NRF52Board.h

@@ -58,6 +58,7 @@ public:
   // A loop blocked forever in SoftDevice-backed flash I/O will stop feeding it
   // and be reset automatically.
   void feedWatchdog(bool enabled = true);
+  void serviceWatchdog() override;
   virtual uint8_t getStartupReason() const override { return startup_reason; }
   virtual float getMCUTemperature() override;
   virtual void reboot() override { NVIC_SystemReset(); }

src/helpers/radiolib/CustomSX1276.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <RadioLib.h>
+#include "MeshCore.h"
 
 #define RH_RF95_MODEM_STATUS_CLEAR               0x10
 #define RH_RF95_MODEM_STATUS_HEADER_INFO_VALID   0x08
@@ -72,7 +73,7 @@ class CustomSX1276 : public SX1276 {
         | RH_RF95_MODEM_STATUS_HEADER_INFO_VALID)) != 0;
     }
 
-    int tryScanChannel(unsigned long timeout_ms = 2000UL) {
+    int tryScanChannel(unsigned long timeout_ms, mesh::MainBoard& board) {
       // start CAD
       int16_t state = startChannelScan();
       RADIOLIB_ASSERT(state);
@@ -81,12 +82,18 @@ class CustomSX1276 : public SX1276 {
       // completed, so wait on its IRQ pins with the same bounded policy used
       // by the generic wrapper.
       const unsigned long started = millis();
+      unsigned long last_watchdog_service = started;
       while(!this->mod->hal->digitalRead(this->mod->getIrq())) {
         this->mod->hal->yield();
         if(this->mod->hal->digitalRead(this->mod->getGpio())) {
           return(RADIOLIB_PREAMBLE_DETECTED);
         }
-        if(millis() - started >= timeout_ms) {
+        const unsigned long now = millis();
+        if(now - last_watchdog_service >= 1000UL) {
+          board.serviceWatchdog();
+          last_watchdog_service = now;
+        }
+        if(now - started >= timeout_ms) {
           return(RADIOLIB_ERR_RX_TIMEOUT);
         }
       }

src/helpers/radiolib/CustomSX1276Wrapper.h

@@ -42,7 +42,7 @@ public:
 
 protected:
   int16_t performChannelScan() override {
-    return ((CustomSX1276 *)_radio)->tryScanChannel();
+    return ((CustomSX1276 *)_radio)->tryScanChannel(CAD_SCAN_TIMEOUT_MS, *_board);
   }
 
   bool radioDeepInit() override {

src/helpers/radiolib/RadioLibWrappers.cpp

@@ -621,9 +621,16 @@ int16_t RadioLibWrapper::performChannelScan() {
   if (result != RADIOLIB_ERR_NONE) return result;
 
   const unsigned long started = millis();
-  while (millis() - started < 2000UL) {
+  unsigned long last_watchdog_service = started;
+  while (millis() - started < CAD_SCAN_TIMEOUT_MS) {
     result = _radio->getChannelScanResult();
     if (result != RADIOLIB_ERR_UNKNOWN) return result;
+
+    const unsigned long now = millis();
+    if (now - last_watchdog_service >= 1000UL) {
+      _board->serviceWatchdog();
+      last_watchdog_service = now;
+    }
     yield();
   }
 

src/helpers/radiolib/RadioLibWrappers.h

@@ -12,6 +12,7 @@
 
 class RadioLibWrapper : public mesh::Radio {
 protected:
+  static constexpr unsigned long CAD_SCAN_TIMEOUT_MS = 10000UL;
   PhysicalLayer* _radio;
   mesh::MainBoard* _board;
   uint32_t n_recv, n_sent, n_recv_errors;