2019-05-07

A Question Of Time

When the Raspberry Pi is used in a mobile environment like a car, there will be times when the Raspberry Pi boots-up without internet connectivity. This creates a problem for the Raspberry Pi since it relies on the internet to set it's internal clock.

The creators of the Raspberry Pi in an attempt to keep hardware costs down, made the decision to build the Raspberry Pi without a Real-Time-Clock (RTC) and instead, rely on Simple Network Time Protocol (SNTP). This is a great solution since most Raspberry Pi's are connected to the internet. But for those of us who deploy Raspberry Pi's as mobile devices away from the internet, this is problematic.

Comvette boots-up and displays the current time whenever the ignition is in the "run" or "accessory" position. At boot-up, the car could be in a parking lot, a rest stop or any number of places where access to the internet isn't available and SNTP cannot be used to set the clock.

So a small, inexpensive, battery powered DS1307 Real Time Clock module from Adafruit.com is installed to provide the current time.

To add a RTC, some re-configuration of the Raspberry Pi is required. The details are covered here:

Adding a Real Time Clock to Raspberry Pi

The RTC keeps the Raspberry Pi's clock set accurately when internet connectivity isn't available and SNTP will be used when internet connectivity is available.