The materials for this document are licensed under the Apache license. See the file LICENSE for details.
Copyright 2016 F Douthit
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0.
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
A real time clock keeps track of the current time for a computer. By current time I mean the time on a wall clock. This might seem strange to you since your PC already does that. Don’t all computers? The answer is no. If you had experience with earlier desktop computers you may have had to replace the clock battery. That clock was the PC’s real time clock.
An RTC keeps time while the computer is not powered. It typically sips power, so that the computer can be unpowered for a long time and when powered on has the correct time.
The RTC modules as used for the Pi (and normal PC) are only used to get the initial time during bootup. It’s updated on normal shutdown to take any ntp corrections etc as well.
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Note
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In particular, single board hobby PCs like the Raspberry Pi and Arduino do not include a real time clock. For some applications this is OK. Some features require the current time, such as networking. |
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Bread Board and Jumper Wires
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Raspberry Pi 2 or 3
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32GB SDCard of Raspberry Pi 2 image.
A data sheet, for our purposes here, documents in a concise manner the features and capabilities of a component.
This is the Datasheet for the DS3231.