I've Googled myself tired on this topic and I see that NTP time synchronization discussions are plentiful in the forums here, so apologies if I am asking a question that has been answered - I really tried to solve this myself lol. I am building an ESP32 based project that needs to trigger a relay o…

It's 3 hours (on ESP32 at least), 10800000 millis. You can check it with a function mentioned below. (BTW, I see "synch" and think it rhymes with "lynch" and "lunch". The band is called NSYNC after all.) The layers of software for ESP32 NTP are your sketch arduino-esp32 board platform (C++) E…

[image] tomkatt20: I would like the NTP update interval to be twice a day Try sntp_set_sync_interval(12UL*60*60*1000);

[image] tomkatt20: I need a loop that occurs every second Try void loop() { static time_t lastNow; time(&now); if (now != lastNow) { // Display time lastNow = now; } }

[image] PaulRB: Try Ironically, I just realized that my time variable should be static so I changed that. But does the suggested code trigger on the exact second? I'd like the clock functionality to delay until the next second rolls over so everything is as 'timely' as possible... That's s…

[image] tomkatt20: while others turn off WiFi after the initial synch so the system time will drift at some point. Most likely to save power. Yes, it will drift over time. You can periodically reenable WiFi and force a resync to NTP. Using SNTP_SYNC_MODE_SMOOTH will ensure that time changes d…

[image] gfvalvo: What does that mean? I think you answered this in your first comment... What I mean is that I see code examples that leave WiFi enabled after the NTP synch and others that disable WiFi to save power. I would expect the configTime() or whatever sets up the NTP synch to expli…

[image] tomkatt20: I half assumed that there might be status functions that could be called to let you know things like when the last sync was done or when the next sync is scheduled, or what the difference was between system clock and NTP when the last sync was performed... These functions are …

[image] tomkatt20: does the suggested code trigger on the exact second? No, but it's as close as you can easily get. It depends what other code is in loop() and how long that takes to run. In the code I suggested, there is nothing else in loop() at all, so it will run thousands of times per s…

Thanks very much for that informative reply - that is the clearest explanation of the NTP update process I have read, and I spent several hours Googling around and even tried to wrap my mind around the Espressif API documentation. I knew that the ESP32 was dual core, but had no idea the libraries c…

Yet Another ESP32 NTP Question (Looping / Update Interval)

Projects Programming

PerryBebbington March 25, 2025, 3:51pm 5

By 'exact second' do you mean the moment the second increments as per international standards? I ran into this problem and never really resolved it, you can read about my efforts here:

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Yet Another ESP32 NTP Question (Looping / Update Interval)

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