@noiasca,
(And anyone else with knowledge of using time libraries on the ESP8266)
Hello Werner,
I am using s slightly modified version of the code on your website here:
https://werner.rothschopf.net/202011_arduino_esp8266_ntp_en.htm
The modification is just to print when the seconds increments instead of after a delay of 1000ms, and I am sending the data to the serial port instead of the USB port.
The ESP8266 board I am using is:
I have an oscilloscope connected to D8, which is the serial Tx pin after doing Serial.swap().
On the other channel of the oscilloscope I have a 1 second pulse from a GPS receiver for reference. My assumption and understanding being that a 1 second pulse from a GPS receiver will be accurate to a few nano seconds, certainly a lot more accurate than required for this test.
What I find is that the time the data is sent, which is driven by when the seconds increment happens, drifts slowly, suggesting the clock is running slightly slow. While I realise the oscillator on the ESP8266 might not have an accurately defined frequency, I would hope that updates from an NTP server would correct for this. I have not yet run a test for long enough to see whether and how the drift is corrected. I would guess that it must be corrected by some means at some point otherwise the RTC will be wrong.
My question is to ask if there is a fix for this, to stop or reduce the drift, also when and how is it corrected? Any other comment or feedback is welcome.
Code:
// NTP using the built in NTP functionality
// https://werner.rothschopf.net/202011_arduino_esp8266_ntp_en.htm
// https://forum.arduino.cc/u/noiasca
// https://forum.arduino.cc/t/ntp-time-on-esp8266-showing-rubbish/936241/3
/*
NTP TZ DST - bare minimum
NetWork Time Protocol - Time Zone - Daylight Saving Time
Our target for this MINI sketch is:
- get the SNTP request running
- set the timezone
- (implicit) respect daylight saving time
- how to "read" time to be printed to Serial.Monitor
This example is a stripped down version of the NTP-TZ-DST (v2)
And works for ESP8266 core 2.7.4 and 3.0.2
by noiasca
2020-09-22
*/
// https://forum.arduino.cc/t/problem-connecting-wifi-with-esp8266-to-send-data-to-google-sheets/944317/3
// ESP8266 status codes
#ifndef STASSID
#define STASSID "xxx" // set your SSID
#define STAPSK "xxx" // set your wifi password
#endif
/* Configuration of NTP */
#define MY_NTP_SERVER "at.pool.ntp.org"
//#define MY_TZ "GMT0BST,M3.5.0/1,M10.5.0"
//#define MY_TZ "CET-1CEST,M3.5.0/02,M10.5.0/03"
#define MY_TZ "AST4"
#define MY_TZGMT "GMT0"
/* Necessary Includes */
#include <ESP8266WiFi.h> // we need wifi to get internet access
#include <time.h> // time() ctime()
//#include <TimeLib.h>
/* Globals */
time_t now; // this is the epoch
tm tm; // the structure tm holds time information in a more convient way
void showTime() {
static time_t lastTime;
time(&now); // read the current time
if (now != lastTime) {
lastTime = now;
localtime_r(&now, &tm); // update the structure tm with the current time
Serial.print("year:");
Serial.print(tm.tm_year + 1900); // years since 1900
Serial.print("\tmonth:");
Serial.print(tm.tm_mon + 1); // January = 0 (!)
Serial.print("\tday:");
Serial.print(tm.tm_mday); // day of month
Serial.print("\thour:");
Serial.print(tm.tm_hour); // hours since midnight 0-23
Serial.print("\tmin:");
Serial.print(tm.tm_min); // minutes after the hour 0-59
Serial.print("\tsec:");
Serial.print(tm.tm_sec); // seconds after the minute 0-61*
Serial.print("\twday:");
Serial.print(tm.tm_wday); // days since Sunday 0-6
if (tm.tm_isdst == 1) // Daylight Saving Time flag
Serial.print("\tDST");
else
Serial.print("\tstandard");
Serial.println();
}
}
void setup() {
Serial.begin(115200);
Serial.println("\nNTP TZ DST - bare minimum");
configTime(MY_TZGMT, MY_NTP_SERVER);
configTime(MY_TZ, MY_NTP_SERVER); // --> Here is the IMPORTANT ONE LINER needed in your sketch!
// start network
WiFi.persistent(false);
WiFi.mode(WIFI_STA);
WiFi.begin(STASSID, STAPSK);
while (WiFi.status() != WL_CONNECTED) {
delay(200);
Serial.print ( "." );
}
Serial.println("\nWiFi connected");
// by default, the NTP will be started after 60 secs
Serial.swap();
}
void loop() {
showTime();
//Serial.print(now);
//delay(1000); // dirty delay
}Oscilloscope traces just after ESP8266 restarted
Yellow trace 1 second reference, blue trace data from serial port on ESP8266
Oscilloscope traces 30 minutes after ESP8266 started
Background to this question
I use several ESP8266s to collect data from weather sensors and send the data along with the date and time to a PIC based controller that displays the weather data and also runs my heating. The weather data is saved to give a 7 day rolling history of the weather. The saved data would have errors in it every day or 2 at random intervals. I traced this to the data occasionally not being saved due to the clock running on the PIC sometimes skipping seconds. I traced that problem to the time data from the ESP8266 jittering by about half a second every 5 minutes or so. I fixed the jittering by adding yield() between every function call in loop() on the ESP8266. The jitter was hiding the drift. Now I see the drift and want to remove or minimise it if possible.
