Aplu (Aegidius Pluess) Miscellaneous

Internet time servers offer time services for several hundred million systems worldwide. They use a standardized data format, the Network Time Protocol (NTP).

The LinkUp's ESP32 uses a library that implements the NTP. With the import of the small module ntptime the functions getTimeRaw() and getTime() are available to the micro:bit programmer, which return the current date time as tuple or in string format.

In the following example the ESP32 logs on to an access point, retrieves the time information about every 10 seconds in raw format from the standard server pool.ntp.org (or from ch.pool.ntp.org). The function getTime() returns the date time information as colon separated fields in a char array. In order to split it, the well-known strtok() algorithm is used.

#include <linkup.h>
#include <string.h>

void setup()
{
  Serial.begin(9600);
  Wire.begin(); 
  char reply[128];
  Serial.println("Connecting...");
  connectAP("myssid", "mypassword", reply);
}

void loop()
{
  char reply[128];
  getNtpTimeRaw("", reply);
//  getNtpTimeRaw("ch.pool.ntp.org", reply);
  Serial.println(reply);
  char* p = strtok(reply, ":");
  Serial.println("yyyy, mm, dd, h, m, s, weekday, dayofyear (GMT)");
  while (p != NULL)
  {
    Serial.println(p);
    p = strtok(NULL, ":");
  }
  delay(10000);
}

2019:9:9:14:53:45:2:252
yyyy, mm, dd, h, m, s, weekday, dayofyear (GMT)
2019
9
9
14
53
45
2
252

With a few lines of code, you can create a continuously running clock that displays the current time very accurately in the termnal window or an attached display. Here you use the libary TimeLib.h that provides some useful time functions. getNtpTime() returns a time_t value (seconds after 1.1.1970) and date time integer values can easily be retrieved with the function day(t), month(t), etc.

// NtpTime2.ino

#include <linkup.h>
#include <TimeLib.h>
#include <ntptime.h>

void setup()
{
  Serial.begin(9600);
  Wire.begin(); 
  char reply[128];
  Serial.println("Connecting...");
  connectAP("myssid", "mypassword", reply);
}

void loop()
{
  time_t t = getNtpTime("pool.ntp.org");
  char date[64];
  sprintf(date, "%d.%d.%d %02d:%02d:%02d", day(t), month(t), year(t), hour(t), minute(t), second(t));
  Serial.println(date);
  delay(10000);  
}

The module ntptime also supports the setSyncProvider() function pointer registration, as seen in the following example:

// NtpTime3.ino

#include <linkup.h>
#include <TimeLib.h>
#include <ntptime.h>

void setup()
{
  Serial.begin(9600);
  Wire.begin(); 
  char reply[128];
  Serial.println("Connecting...");
  connectAP("myssid", "mypassword", reply);
  setSyncProvider(getNtpTime);
}

void loop()
{
  time_t t = now();
  char date[64];
  sprintf(date, "%d.%d.%d %02d:%02d:%02d", day(t), month(t), year(t), hour(t), minute(t), second(t));
  Serial.println(date);
  delay(10000);  
}

You can create a real digital clock and display the current time on a 4-digit 7-segment display based on the TM1637 chip. The library TM1637Display found on GitHub has been extended with setColon() to turn on the colon in the center of the display (files included in LinkUp distribution).

// NtpTime4.ino

#include <linkup.h>
#include <TimeLib.h>
#include <ntptime.h>
#include <TM1637Display.h>

#define CLK 2
#define DIO 3

TM1637Display display(CLK, DIO);

void clear()
{
  uint8_t data[4] = {0, 0, 0, 0};
  display.setSegments(data);
}

void setup()
{
  Wire.begin(); 
  display.setColon(true);
  display.setBrightness(0x0f);
  char reply[128];
  connectAP("raspilink", "aabbaabbaabb", reply);
  setSyncProvider(getNtpTime);
}

void loop()
{
  time_t t = now();
  int mez = hour(t) + 1; // MEZ summer time
  int time = mez * 100 + minute(t);
  clear();
  display.showNumberDec(time, false, 4, 0);
  delay(10000);  
}

NTP time server