optional RTC 3231 integration

src/time_manager.cpp

@@ -1,10 +1,12 @@
 #include "time_manager.h"
 #include "compressor.h"
 #include "config.h"
+#include "rtc_ds3231.h"
 #include <time.h>
 
 static bool g_time_synced = false;
 static bool g_tz_set = false;
+static bool g_rtc_present = false;
 
 void time_receiver_init(const char *ntp_server_1, const char *ntp_server_2) {
   const char *server1 = (ntp_server_1 && ntp_server_1[0] != '\0') ? ntp_server_1 : "pool.ntp.org";
@@ -40,6 +42,10 @@ void time_set_utc(uint32_t epoch) {
   tv.tv_usec = 0;
   settimeofday(&tv, nullptr);
   g_time_synced = true;
+
+  if (g_rtc_present) {
+    rtc_ds3231_set_epoch(epoch);
+  }
 }
 
 void time_send_timesync(uint16_t device_id_short) {
@@ -101,3 +107,30 @@ void time_get_local_hhmm(char *out, size_t out_len) {
   localtime_r(&now, &timeinfo);
   snprintf(out, out_len, "%02d:%02d", timeinfo.tm_hour, timeinfo.tm_min);
 }
+
+void time_rtc_init() {
+  if (!ENABLE_DS3231) {
+    g_rtc_present = false;
+    return;
+  }
+  g_rtc_present = rtc_ds3231_init();
+}
+
+bool time_try_load_from_rtc() {
+  if (!g_rtc_present) {
+    return false;
+  }
+  if (time_is_synced()) {
+    return true;
+  }
+  uint32_t epoch = 0;
+  if (!rtc_ds3231_read_epoch(epoch) || epoch == 0) {
+    return false;
+  }
+  time_set_utc(epoch);
+  return true;
+}
+
+bool time_rtc_present() {
+  return g_rtc_present;
+}