NEC MPI4E Raspberry Pi Compute Module Setup Guide

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Raspberry Pi OS includes an overlay for directly monitoring a GPIO used for signaling system shutdown.

The configuration settings can be made directly to the “config.txt” file by adding a line such as the

following example:

dtoverlay=gpio-shutdown,gpio_pin=23

See the following information for configuring the various boot overlay options:

https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README

Alternatively, an example Python script rpi_shutdown.py is included with the Python based NEC PD

SDK. The script shows how to monitor GPIO 23 for a high to low transition, and how to use this to

gracefully shutdown the Operating System on the Compute Module before power to the module is

removed by the display. Normally this script should be started when the Operating System starts. This

can be accomplished by adding it to the /etc/rc.local file on the system. See the instructions

provided in the sample file for more details.

5.11 Reading and setting the display’s internal Real Time Clock (RTC)

from the OS

The Compute Module does not include a Real Time Clock, so the correct time must be configured at each

startup. This is usually done via a network connection to an NTP time server; however, the Compute

Module can read the display’s internal Real Time Clock as well.

The display’s internal Real Time Clock can be read and set from the Compute Module via the internal

serial connection (UART). This can be useful in situations where the Compute Module is unable to get the

current time from the network.

The Python based NEC PD SDK includes the following sample files:

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NEC MPI4E RaspberryPi 4 System on a Chip Solution