NTPClient library is working without any code to establish a network connection!

Other Hardware 3rd Party Boards
1

Currently, I have an older ESP8266 plugged into a handy USB to ESP-01 adapter.

8266
8266988×703 70.6 KB

I uploaded a simple sketch (below) to retrieve Time using NTPClient:

#include <NTPClient.h>
#include <WiFiUdp.h>

WiFiUDP ntpUDP;
NTPClient ntpClient(ntpUDP, "pool.ntp.org", -18000, 60000);

void setup() {

  Serial.begin(115200);

  Serial.println();
  Serial.println();
  Serial.println();

  for (uint8_t t = 5; t > 0; t--) {
    Serial.printf("[SETUP] WAIT %d...\n", t);
    Serial.flush();
    delay(1000);
  }
 
  ntpClient.begin();
}

void loop() {

  ntpClient.update();
  Serial.print("NTP time: ");
  Serial.print(ntpClient.getFormattedTime());
  Serial.print(" ");
  Serial.print(ntpClient.getEpochTime());
  Serial.println();

  Serial.println("Wait 5s before next round...");
  delay(5000);
}

Notice that in no way do I establish any kind of IP connection in the code, yet when I upload the sketch, unplug the adapter and plug it back in to run the sketch, I get working results in the Serial monitor:

8266-2
8266-2450×208 3.19 KB

I would expect my code to fail at this point, but I can only surmise that the USB to ESP-01 adapter provides a working connection to the 8266 that is plugged into it. If that case, how can I determine (from within the sketch) what the IP address might be?

2

You can You can query the IP address using WiFi.localIP() from within your sketch. But to do this, you need to #include <ESP8266WiFi.h>. using WiFi.localIP() from within your sketch. But to do this, you need to #include <ESP8266WiFi.h>.

3

Thanks. I tried that, but I get back "(IP unset)". I also tried it with Ethernet.h, but get the same result.

4

you don't need an external library for NTP on an ESP8266.
The ESP Plattform package comes with everything you need for NTP on an ESP8266.

see:

1 Like
5

Thank you for that information, it is helpful.

But, I'm trying to figure out how NTP is working on my 8266 when I have not established any kind of network connection within the sketch itself. Somehow, the board has enough access to the Internet that NTP is reporting proper time.

6

This is done by the ESP in the background - may be due to a previous sketch you had on your ESP before this outdated NTP sketch.

You can try to delete the stored wifi data:

grafik

1 Like
7

It remembers an old connection.

If you Call WiFi.disconnect(true); in the setup() that will clear saved credentials.

2 Likes