Some popular RTC can miss up to several seconds on a month, so it must be updated once in a while. Even most accurate RTC has to be set to the correct time at least one.
On this example, we update/setup an RTC module from a NTP service with a ESP8266/ESP32 development board and an OLED module.
The WEMOS D1 mini is a popular ESP8266 development board, with its own ecosystem of shields. The MH ET LIVE ESP32MiniKit is an ESP32 development board, compatible with the d1 mini shields. Pick one of this boards, an 64x48 oled shield, some proto board ahd headers, and get soldering.
We use the arduino framework for the ESP8266 or the ESP32 depending of the board of your choice. For easy of use, this example is set up as a platformio project.
For the OLED, we use the esp8266-oled-ssd1306 library. NTP syncronized time is provided by the core/HAL time libraries included on the ESP8266/ESP32 frameworks. Different RTC ICs are read and updated using the RTC class from the UxTClib library.
# install the libraries (one time setup)
pio lib install ESP8266_SSD1306 # set wifi credentials (on each new terminal session)
export WIFI_SSID=myWIFIssid WIFI_PASS=myWIFIpass
# compile & upload for d1_mini (esp8266)
pio run -e d1_mini
pio run -e d1_mini -t upload
# compile & upload for mhetesp32minikit (esp32)
pio run -e mhetesp32minikit
pio run -e mhetesp32minikit -t upload