Time

FED4 RTC (Real-Time Clock) Functionality

The FED4 uses a DS3231 RTC on the secondary I2C bus to keep accurate time across power cycles. Time is used for logs, display, and scheduling.

Initialization and auto-update

• initializeRTC() — starts the DS3231 and loads time into the internal clock. On new compilation, the RTC is updated to the build time.
• Compilation detection — a stored compile timestamp in Preferences triggers updateRTC() only when firmware changes.

Key API

• now() — returns DateTime from the RTC.
• updateTime() — updates currentHour, currentMinute, currentSecond, unixtime.
• adjustRTC(timestamp) — sets RTC from a Unix timestamp (used by Hublink time sync).

Logging

• ElapsedSeconds in the SD log is millis-based, rounded to 0.001 s (1 ms resolution).

Manual set

• menuRTC() — interactive RTC setting in the FED4 menu.

See FED4_RTC.cpp, RTClib.