UL recognized to ensure against reverse charging current when utilized as a part of conjunction with a lithium battery. A lithium battery with 48mAhr or greater will backup the DS1307 for more than 10 years in the absence of power at 25✬. The nominal write protect trip point voltage at which access to the RTC and user RAM is denied is set by the internal circuitry as 1.25 x VBAT nominal. The output of the internal oscillator, X2 is drifted if an external oscillator is connected to X1.īattery input for any standard 3V lithium cell or other energy source.īattery voltage should be between 2V and 3.5V for suitable operation. X1 is the input to the oscillator and can alternatively be connected to an external 32.768 kHz oscillator. The internal oscillator circuitry is intended for operation with a crystal having a specified load capacitance of 12.5pF. Tips for Writing Bulletproof Real-Time Clock Control CodeĬonnections for standard 32.768 kHz quartz crystal.Timekeeping operation continues while the part operates from the backup supply. The DS1307 has a built-in power-sense circuit that detects power failures and automatically switches to the backup supply. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. Address and data are transferred serially through an I2C, bidirectional bus. The DS1307 serial real-time clock (RTC) is a low-power, full binary-coded decimal (BCD) clock/calendar plus 56 bytes of NV SRAM. For example, in Arduino, you use the mills() function to return the internal timer counter value. They do not maintain month, day, year, hour, minute, etc.When power is removed, the internal timers are reset to 0. The problem with these internal timers is twofold: These timers are initialized on power-up and are fairly accurate. Virtually all micro-controllers have a built-in timers (including all Arduino’s). The articles and references used here have been listed below. My goal is to bring the best of that information into a single place for you to use as a reference. There are many, probably thousands, of articles on RTC’s and how to interface them with an Arduino. When you find yourself needing a RTC for your project, this article will help guide you to completion. There are many applications where a real time clock (RTC) is of use for display, data logging with date/time stamp, etc.
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