Time / SNTP functions

mg_millis()

uint64_t mg_millis(void);

Return milliseconds since boot (uptime). Never goes backwards. On RTOS targets (FreeRTOS, ThreadX, Zephyr, etc.) uses the RTOS tick count. On STM32/Cube uses HAL_GetTick(). On Arduino uses millis(). On Linux/macOS uses CLOCK_MONOTONIC_RAW or CLOCK_MONOTONIC; falls back to CLOCK_REALTIME if neither is available.

mg_boot_timestamp_ms

extern uint64_t mg_boot_timestamp_ms;

Boot timestamp in ms since Epoch. Updated by successful SNTP request

mg_now()

uint64_t mg_now(void);

Return milliseconds since Epoch: mg_millis() + mg_boot_timestamp_ms. Until a successful SNTP request completes, this is identical to mg_millis().

mg_timer_expired()

bool mg_timer_expired(uint64_t *expiration, uint64_t period, uint64_t now);

Return true if the periodic timer has fired; advance expiration by one period. Handles wrap-around. Usage example:

uint64_t timer = 0;
for (;;) {
  if (mg_timer_expired(&timer, 1000, mg_millis())) {
    MG_INFO(("Hi"));  // Print a message every second
  }
  mg_mgr_poll(&mgr, 10);
}

mg_sntp_connect()

struct mg_connection *mg_sntp_connect(struct mg_mgr *mgr, const char *url,
                                      mg_event_handler_t fn, void *fn_data);

Connect to an SNTP server and send a time request. url defaults to "udp://time.google.com:123" when NULL. On success the internal boot timestamp is updated so that mg_now() returns the correct wall-clock time, and MG_EV_SNTP_TIME is fired on fn (if not NULL) with a pointer to the int64_t epoch in milliseconds. Pass fn == NULL and fn_data == NULL for a fire-and-forget sync that only updates mg_boot_timestamp_ms. Typical polling usage:

uint64_t timer = 0;
for (;;) {
  uint64_t period = mg_boot_timestamp_ms == 0 ? 1000 : 3600 * 1000;
  if (mg_timer_expired(&timer, period, mg_millis())) {
    mg_sntp_connect(&mgr, NULL, NULL, NULL);
  }
  mg_mgr_poll(&mgr, 1000);
}