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SparkFun Real Time Clock Module - RV-1805 (Qwiic)

Get with the times, already! This SparkFun Real Time Clock (RTC) Module is a Qwiic-enabled breakout board for the RV-1805 chipset. The RTC is ultra-low power (running at only about 22nA in its lowest power setting) so it can use a supercapacitor for backup power instead of a normal battery. This means you get plenty of charge and discharge cycles without any degradation to the “battery." To make it even easier to get your readings, all communication is enacted exclusively via I2C, utilizing our handy Qwiic system so no soldering is required to connect it to the rest of your system. However, we still have broken out 0.1"-spaced pins in case you prefer to use a breadboard.

This RTC module's built in RV-1805 has not one, but two internal oscillators: a 32.768kHz tuning fork crystal and a low power RC based oscillator and can automatically switch between the two using the more precise crystal to correct the RC oscillator every few minutes. This feature allows the module to maintain a very accurate date and time with the worst case being +/- about three minutes over a year. The RV-1805 also has a built in trickle charger so as soon as the RTC is connected to power the it will be fully charged in under 10 minutes and has the ability to switch power to other systems allowing it to directly turn on or off a power hungry device such as a microcontroller or RF engine.

There is also the option to add a battery to the board if the supercapacitor just isn’t going keep your project powered long enough (keep in mind, the supercap can hypothetically make the board keep time for around 35 days), you can solder on an external battery. That means you can let board sit with no power or connection to the outside world and the current hour/minute/second/date will be maintained.


The SparkFun Qwiic connect system is an ecosystem of I2C sensors, actuators, shields and cables that make prototyping faster and less prone to error. All Qwiic-enabled boards use a common 1mm pitch, 4-pin JST connector. This reduces the amount of required PCB space, and polarized connections mean you can’t hook it up wrong.


  • Operating Voltage (Startup): 1.6V - 3.6V
  • Operating Voltage (Timekeeping): 1.5V - 3.6V
  • Operating Temperature: -40°C - 85°C
  • Time Accuracy: ±2.0 ppm
  • Current Consumption: 22nA (Typ.)
  • I2C Address: 0xD2
  • Supercapacitor for Backup Power
  • 2x Internal Oscillators
  • 2x Qwiic Connectors

SparkFun Real Time Clock Module - RV-1805 (Qwiic) Product Help and Resources

Qwiic Real Time Clock Module (RV-1805) Hookup Guide

May 31, 2018

Find out what time it is, even after the power's been out on your project for a while with the Qwiic Real Time Clock (RTC) module.

Core Skill: Programming

If a board needs code or communicates somehow, you're going to need to know how to program or interface with it. The programming skill is all about communication and code.

3 Programming

Skill Level: Competent - The toolchain for programming is a bit more complex and will examples may not be explicitly provided for you. You will be required to have a fundamental knowledge of programming and be required to provide your own code. You may need to modify existing libraries or code to work with your specific hardware. Sensor and hardware interfaces will be SPI or I2C.
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Core Skill: Electrical Prototyping

If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.

2 Electrical Prototyping

Skill Level: Rookie - You may be required to know a bit more about the component, such as orientation, or how to hook it up, in addition to power requirements. You will need to understand polarized components.
See all skill levels


Comments

Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • Timestamping... Can this RTC module be used to timestamp a sensor measurement (date+time) to high precision, like microseconds or better? In other words, is there a library command that allows me to grab an accurate timestamp at any time (not just on even second increments)? Thanks!

    • The RV-1805 maintains accuracy up to hundredths of a second (refer to app manual sec 3.1: Register Overview). Might be useful to also note that the RV-1805 is not recommended for new designs by the manufacturer and has been replaced by the RV-3028 which is only maintains accuracy up to whole seconds.

      Additionally, in ideal conditions the crystal is accurate to 2.0 ppm, which is a drift of aprox. 0.173 sec per day. This suggests it might not be suited to your application.

  • Is the I/O 5-Volt complaint?

  • Does this come with the supercapacitor on board? I can't see the photos.

  • what is the difference between this product and the DS3234? (other than Qwiic compatibility)

    • This guy is super low power (22nA in the proper configuration) and drifts about half as much (+- 2PPM as opposed to +-3.5PPM)

      • Since it took me a while to wrap my head around all of the drift maths, I just realized a point that might be useful to others:

        In an ideal environment of 25°C, both the RV-1805 and the DS3234 are spec'd at 2ppm drift. However, the DS3234 is temperature-compensated, and will never drift more than 3.5ppm when used within its operating range. On the other hand, the RV-1805 is not temperature-compensated and it can accumulate up to ±140ppm at the extremes of its operating temperature range (refer to app manual sec 6.5: XT FREQUENCY CHARACTERISTICS).

Customer Reviews

3 out of 5

Based on 2 ratings:

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Poor

Drifts, even with the battery. Difficult to set to correct time

Works Well and Easy to Use

It was easy to follow the code in the examples to get this configured and running. It wasn't super accurate in the default configuration. But maybe i need to work on switching to the crystal. Nice tutorial!