Keep time across reset for NRF52

src/helpers/ArduinoHelpers.cpp

@@ -0,0 +1,6 @@
+#include <stdint.h>
+
+extern "C" {
+    __attribute__((section(".persistent_magic"))) uint32_t persistent_magic;
+    __attribute__((section(".persistent_data"))) uint32_t persistent_time;
+}

src/helpers/ArduinoHelpers.h

@@ -3,19 +3,57 @@
 #include <Mesh.h>
 #include <Arduino.h>
 
+#ifdef NRF52_PLATFORM
+#define CLOCK_MAGIC_NUM        0xAA55CC33
+#define RTC_TIME_MIN           1772323200  // 1 Mar 2026
+
+extern uint32_t persistent_magic;
+extern uint32_t persistent_time;
+#endif
+
 class VolatileRTCClock : public mesh::RTCClock {
   uint32_t base_time;
   uint64_t accumulator;
   unsigned long prev_millis;
+
 public:
-  VolatileRTCClock() { base_time = 1715770351; accumulator = 0; prev_millis = millis(); }   // 15 May 2024, 8:50pm
+  VolatileRTCClock() {
+#ifdef NRF52_PLATFORM
+    if (persistent_magic == CLOCK_MAGIC_NUM && persistent_time >= RTC_TIME_MIN) {
+      base_time = persistent_time;
+    } else {
+      base_time = RTC_TIME_MIN;
+    }
+#else
+    base_time = 1715770351;
+#endif
+
+    accumulator = 0;
+    prev_millis = millis();
+  }
+
   uint32_t getCurrentTime() override { return base_time + accumulator/1000; }
-  void setCurrentTime(uint32_t time) override { base_time = time; accumulator = 0; prev_millis = millis(); }
+
+  void setCurrentTime(uint32_t time) override {
+    base_time = time;
+    accumulator = 0;
+    prev_millis = millis();
+
+#ifdef NRF52_PLATFORM
+    persistent_magic = CLOCK_MAGIC_NUM;
+    persistent_time = time;
+#endif
+  }
 
   void tick() override {
     unsigned long now = millis();
     accumulator += (now - prev_millis);
     prev_millis = now;
+
+#ifdef NRF52_PLATFORM
+    persistent_magic = CLOCK_MAGIC_NUM;
+    persistent_time = getCurrentTime();
+#endif
   }
 };