rpi_autodisplay

I have been looking into how to automatically adjust the brightness of the official 7" Raspberry Pi touchdisplay to the ambient brightness. This should behave similar to a smartphone or modern laptop screen and turn off the display when it is completely dark. So, if it is super bright in a room (in lux), then the brightness value (in %) should be accordingly high. If it is rather dark, then the display should also be dimmed. In addition, I would like to have a connection to openHAB and here to adjust the automatic brightness and also the display on and off. As a brightness sensor I will use the BH1750 sensor and as a software solution comes a Python script with the appropriate libraries to the course.

Features

• Autobrightness Controll of your Raspberry Pi's Touchdisplay
• Automatic Display Power Off when it is dark
• MQTT Support
• Homie MQTT Convetion Support
  • openHAB MQTT autodiscovery functional
• possible openHAB integration

Requirements

• Raspberry Pi (2, 3, 4)
• Raspberry Pi's official 7" touchdisplay
• BH1750 light sensor
• Raspbian installation
• python3
• python3 libraries
• i2c bus
• optional: MQTT Broker and openHAB (only for rpi_autodisplay-mqtt.py and rpi_autodisplay-homie.py)
• optional: openHAB Setup or other homie MQTT compatible Smart Home System

raspi-config nonint do_i2c 0
apt install -y python3 python3-smbus i2c-tools python3-pip python3-systemd
# for MQTT Support
apt install -y python3-paho-mqtt
pip3 install --user adafruit-circuitpython-bh1750 rpi-backlight

Installation

cd /usr/src/
git clone https://github.com/alaub81/rpi_autodisplay.git
cp rpi_autodisplay/*.py /usr/local/sbin/
cp rpi_autodisplay/display.service /etc/systemd/system/
chmod +x /usr/local/sbin/rpi_autodisplay*.py

Configuration

rpi_autodisplay.py

if you just like to use the stuff without MQTT you do not need to configure anything. Just enable the systemd service.

systemd daemon-reload
systemctl enable display.service
systemctl start display.service

rpi_autodisplay-mqtt.py

If you like to use the mqtt or homie version, you have to configure the MQTT connection settings in the /usr/local/sbin/rpi_autodisplay-mqtt.py or in /usr/local/sbin/rpi_autodisplay-homie.py:

# MQTT Config
broker = "FQDN / IP ADDRESS" # --> Broker FQDN or IP address
port = 8883 # --> MQTT Broker TCP Port (8883 for the TLS Port, 1883 for the standard Port)
publish_topic="home/attic/office" # --> in which topic you want to publish
clientid = "client-dp" # --> MQTT Client ID, should be unique.
hostname = "clientname" # --> In this topic the helping MQTT values are published (lux goes directly into the topic)
username = "mosquitto" # --> MQTT username, if authentication is used
password = "password" # --> MQTT password, if authentication is used
insecure = True # --> if using a self signed certificate
qos = 1 # --> MQTT QoS level (0, 1, 2) 
retain_message = True # --> publish as a retained mqtt message (True, False)

for Homie MQTT Convention Script

# MQTT Config
broker = "FQDN / IP ADDRESS" # --> Broker FQDN or IP address
port = 8883 # --> MQTT Broker TCP Port (8883 for the TLS Port, 1883 for the standard Port)
mqttclientid = "clientid-dp-homie" # --> MQTT Client ID, should be unique.
clientid = "clientid-dp" # --> Homie Clientid, should be unique.
clientname = "Clientname Display" # --> Homie, human readable client name for the clientid
username = "mosquitto" # --> MQTT username, if authentication is used
password = "password" # --> MQTT password, if authentication is used
insecure = True # --> if using a self signed certificate
qos = 1 # --> MQTT QoS level (0, 1, 2), must be at least 1 for the homie Convention!
retain_message = True # --> publish as a retained mqtt message (True, False), must be True for the homie Convention!

And you have to edit the /etc/systemd/system/display.service. Here you need to change the stuff for the rpi_autodisplay-mqtt.py

...

# Starting after System is online and docker is running
# Only needed if MQTT is used
Wants=network-online.target
After=network-online.target
# Only needed if MQTT Broker is running in a Docker Container on the same Host
#After=docker.service
#After=docker.socket

...

# Command to execute when the service is started
# Without MQTT
#ExecStart=/usr/bin/python3 /usr/local/sbin/rpi_autodisplay.py
# Command to execute when the service is started
# With MQTT
ExecStart=/usr/bin/python3 /usr/local/sbin/rpi_autodisplay-mqtt.py
# With Homie MQTT Convention Support
#ExecStart=/usr/bin/python3 /usr/local/sbin/rpi_autodisplay-homie.py

... 

now you could also enable and start the systemd service

systemd daemon-reload
systemctl enable display.service
systemctl start display.service

Testing

Check if the service is runnig:

systemctl status display.service

Just test it with a flaslight and with covering the sensor with your hand. You should see the display changing its brightness and even going off and on. If you are using the MQTT Scripts just check for example with MQTT Explorer if the topics and payloads are published.

Whole Documentation of that Project:

More Informations here (Sorry, it's german, but just use your browsers transaltion tool): Raspberry Pi Touchdisplay Helligkeit automatisch justieren

Questions, Help, Feedback

if you have any questions, you need help, or just have feedback for my first project here, just let me know!