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NTP Based Digital Clock Panel Driver

Highly accurate, Ethernet base, 7-segment clock driver with built-in NTP client.

This project introduces an open-source, ATmega328 based, configurable NTP clock with a 2.3-inch, 7-segment display driver. This clock automatically obtains time from the configured NTP server and updates the date and time of the built-in RTC (real-time clock). If the connection to the NTP server is lost, the clock continues to run using its built-in RTC.

All the parameters of this clock can configure using its USB base serial terminal. The firmware of this clock supports both static and DHCP addressing modes. Apart from that, parameters such as NTP server address, time-offset, and clock display formats can change through the menu-driven configuration terminal.

This clock is designed to drive large common-anode, 7-segment displays. The prototype version is assembled using four individual segments of 7.2V, 2.3-inch, red color displays (FJS23101BH). To archive, the necessary high output voltage and the current, the 7-segment display output stage of this clock is formed using ULN2803 Darlington transistor array and BC858 transistors.

The network component of this clock is built around the ENC28J60 10BASE-T stand-alone Ethernet controller.

Highly accurate DS3231M RTC is using in this clock for time-keeping operations. To backup the date and time, the CR1220 type button cell is included in the PCB. The date and time are syncs with the NTP server during the system startup. Users can manually initiate synchronization by pressing the “SYNC” button in the system.

Depending on the NTP server, the user needs to specify the time offset to the system to get the correct local time. Time offset can configure using the system configuration menu, and it must be input in a standard format like +5:30.”

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