I was disappointed with the internal RTC accuracy.
It gained 20 seconds in 10 minutes.
I note that other people have found the RTC to be not highly accurate. Since there is no crystal-controlled oscillator on board, I expected some deviation, but not that much. I solved my problem by regularly updating via NTP. Polling the NTP servers constantly is not recommended, as they may consider it a denial of service attack or similar. Taking a guess that a 10 minute interlude is acceptable, I re-wrote the code for their example. Make sure you check the time zone offset for your location.
Changes:
Added variables NTPcheck, NTPdelay and NTPdiff
Extracted the NTP access code into its own routine void(NTP)
Changed and added code at the end to update every 10 minutes.
FULL CODE
// Arduino R4 WiFi Get time from NTP
// Include the RTC library
#include "RTC.h"
//Include the NTP library
#include <NTPClient.h>
#if defined(ARDUINO_PORTENTA_C33)
#include <WiFiC3.h>
#elif defined(ARDUINO_UNOWIFIR4)
#include <WiFiS3.h>
#endif
#include <WiFiUdp.h>
#include "arduino_secrets.h"
int NTPCheck;
int NTPdelay;
int NTPdiff = 0;
///////Enter login data in the Secret tab/arduino_secrets.h
char ssid[] = SECRET_SSID; // network SSID
char pass[] = SECRET_PASS; // network password
int wifiStatus = WL_IDLE_STATUS;
WiFiUDP Udp; // A UDP instance to let us send and receive packets over UDP
NTPClient timeClient(Udp);
void printWifiStatus() {
// print the SSID of the network you're attached to:
Serial.print("SSID: ");
Serial.println(WiFi.SSID());
// print your board's IP address:
IPAddress ip = WiFi.localIP();
Serial.print("IP Address: ");
Serial.println(ip);
// print the received signal strength:
long rssi = WiFi.RSSI();
Serial.print("signal strength (RSSI):");
Serial.print(rssi);
Serial.println(" dBm");
}
void connectToWiFi() {
// check for the WiFi module:
if (WiFi.status() == WL_NO_MODULE) {
Serial.println("Communication with WiFi module failed!");
// don't continue
while (true)
;
}
String fv = WiFi.firmwareVersion();
if (fv < WIFI_FIRMWARE_LATEST_VERSION) {
Serial.println("Please upgrade the firmware");
}
// attempt to connect to WiFi network:
while (wifiStatus != WL_CONNECTED) {
Serial.print("Attempting to connect to SSID: ");
Serial.println(ssid);
// Connect to WPA/WPA2 network.
wifiStatus = WiFi.begin(ssid, pass);
// wait 10 seconds for connection:
delay(10000);
}
Serial.println("Connected to WiFi");
printWifiStatus();
}
void NTP() {
// Get the current date and time from an NTP server and convert
// Time Zone offset for Cairns is 10 hours
auto timeZoneOffsetHours = 10;
auto unixTime = timeClient.getEpochTime() + (timeZoneOffsetHours * 3600);
RTCTime timeToSet = RTCTime(unixTime);
RTC.setTime(timeToSet);
}
void setup() {
Serial.begin(9600);
while (!Serial)
;
connectToWiFi();
RTC.begin();
Serial.println("\nStarting connection to server...");
timeClient.begin();
timeClient.update();
// Get the current time from NTP
NTP();
}
void loop() {
RTCTime currentTime;
// Get current time from RTC
RTC.getTime(currentTime);
// Print out date (DD/MM//YYYY)
Serial.print(currentTime.getDayOfMonth());
Serial.print("/");
Serial.print(Month2int(currentTime.getMonth()));
Serial.print("/");
Serial.print(currentTime.getYear());
Serial.print(" - ");
// Print time (HH/MM/SS)
Serial.print(currentTime.getHour());
Serial.print(":");
Serial.print(currentTime.getMinutes());
Serial.print(":");
Serial.println(currentTime.getSeconds());
delay(1000);
// After 10 minutes, call NTP to set the RTC time again
if (NTPdiff == 0) {
NTPCheck = currentTime.getMinutes();
NTPdelay = currentTime.getMinutes();
NTPdiff = 1;
} else {
NTPdelay = currentTime.getMinutes();
if (NTPdelay - NTPCheck <= 9) {
} else {
NTP();
NTPdiff = 0;
Serial.println("NTP Updated");
}
}
}
