Enable watchdog, and issue a WDT reset when the button is pushed for more than 7s.

src/drivers/Watchdog.cpp

@@ -0,0 +1,60 @@
+#include <mdk/nrf52.h>
+#include <mdk/nrf52_bitfields.h>
+#include <nrf_soc.h>
+#include "Watchdog.h"
+using namespace Pinetime::Drivers;
+
+
+void Watchdog::Setup(uint8_t timeoutSeconds) {
+  NRF_WDT->CONFIG &= ~(WDT_CONFIG_SLEEP_Msk << WDT_CONFIG_SLEEP_Pos);
+  NRF_WDT->CONFIG |= (WDT_CONFIG_HALT_Run << WDT_CONFIG_SLEEP_Pos);
+
+  NRF_WDT->CONFIG &= ~(WDT_CONFIG_HALT_Msk << WDT_CONFIG_HALT_Pos);
+  NRF_WDT->CONFIG |= (WDT_CONFIG_HALT_Pause << WDT_CONFIG_HALT_Pos);
+
+  /* timeout (s) = (CRV + 1) / 32768 */
+  // JF : 7500 = 7.5s
+  uint32_t crv = (((timeoutSeconds*1000u) << 15u) / 1000) - 1;
+  NRF_WDT->CRV = crv;
+
+  /* Enable reload requests */
+  NRF_WDT->RREN = (WDT_RREN_RR0_Enabled << WDT_RREN_RR0_Pos);
+}
+
+void Watchdog::Start() {
+  NRF_WDT->TASKS_START = 1;
+}
+
+void Watchdog::Kick() {
+  NRF_WDT->RR[0] = WDT_RR_RR_Reload;
+}
+
+Watchdog::ResetReasons Watchdog::ResetReason() {
+  uint32_t resetReason;
+  sd_power_reset_reason_get(&resetReason);
+  sd_power_reset_reason_clr(0xFFFFFFFF);
+  if(resetReason & 0x01) return ResetReasons::ResetPin;
+  if((resetReason >> 1) & 0x01) return ResetReasons::Watchdog;
+  if((resetReason >> 2) & 0x01) return ResetReasons::SoftReset;
+  if((resetReason >> 3) & 0x01) return ResetReasons::CpuLockup;
+  if((resetReason >> 16) & 0x01) return ResetReasons::SystemOff;
+  if((resetReason >> 17) & 0x01) return ResetReasons::LpComp;
+  if((resetReason >> 18) & 0x01) return ResetReasons::DebugInterface;
+  if((resetReason >> 19) & 0x01) return ResetReasons::NFC;
+  return ResetReasons::HardReset;
+}
+
+const char *Watchdog::ResetReasonToString(Watchdog::ResetReasons reason) {
+  switch(reason) {
+    case ResetReasons::ResetPin: return "Reset pin";
+    case ResetReasons::Watchdog: return "Watchdog";
+    case ResetReasons::DebugInterface: return "Debug interface";
+    case ResetReasons::LpComp: return "LPCOMP";
+    case ResetReasons::SystemOff: return "System OFF";
+    case ResetReasons::CpuLockup: return "CPU Lock-up";
+    case ResetReasons::SoftReset: return "Soft reset";
+    case ResetReasons::NFC: return "NFC";
+    case ResetReasons::HardReset: return "Hard reset";
+    default: return "Unknown";
+  }
+}

src/drivers/Watchdog.h

@@ -0,0 +1,17 @@
+#pragma once
+
+namespace Pinetime {
+  namespace Drivers {
+    class Watchdog {
+      public:
+        enum class ResetReasons { ResetPin, Watchdog, SoftReset, CpuLockup, SystemOff, LpComp, DebugInterface, NFC, HardReset };
+        void Setup(uint8_t timeoutSeconds);
+        void Start();
+        void Kick();
+
+        ResetReasons ResetReason();
+        static const char* ResetReasonToString(ResetReasons reason);
+
+    };
+  }
+}