Industrial Shields Raspberry PLC 19R+, Quick User Manual

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Rev. 8: 29-04-2021
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RTC
Raspberry PLC RTC Module is based on the DS3231 Chip. This chip works with the I2C protocol
communication, so it is required to have enabled the I2C protocol. It is powered by a button
battery (CR1216 or CR1220).
There are two types of date-time clocks in a Linux system:
The Hardware Clock: This clock is an independent hardware device, with its own power
domain (battery, capacitor, etc), that operates when the machine is powered off, or even
unplugged.
The System Clock: This clock is part of the Linux kernel and is driven by a timer interrupt. It has
meaning only while Linux is running on the machine. The System Time is the number of
seconds since 00:00:00 January 1, 1970 UTC. The System Time is not an integer, though. It has
virtually infinite precision.
To read the Hardware Clock and print its time to standard output in the ISO 8601 format, type
the following:
hwclock -r
To set the Hardware Clock to the time given by the --date option, and update the
timestamps in /etc/adjtime, exec:
sudo hwclock --set --date="2021-04-22 16:25"
For more information about hwclock, exec the following command:
man hwclock.
uSD
The micro-SD contains all the configurations to work properly with the Raspberry PLC.
Consequently, the micro-SD should not be manipulated because without it the Raspberry PLC
would not work correctly.
UPS Shield
All Raspberry PLC Family devices include the UPS Shield. It is a Plug & Play UPS Smart Shield
that provides 5 seconds of electricity in front of a power supply cut off. This extra time of
electricity provides that the Raspberry follow a correct Shut Down process, avoiding any SD
corruption issue. The recharge time of the UPS is less than 1 minute, and the reconnecting