Announcement Box

Linux box with a loudspeaker and an emergency light to be used for announcements and notifications.

Hardware

• SBC with GPIOs and sound output :: OrangePi Zero with an expansion board
• PA system
  • speaker :: 30W, 4 Ohms horn loudspeaker
  • sound amplifier :: mono 18W sound amplifier
  • relay module :: 12V low trigger relay
• Warning Light system
  • warning light :: 12V 10W rotary orange warning light
  • relay module :: 12V low trigger relay

Software

• Operating System - Linux :: Armbian Bullseye for the OrangePi Zero
• PA System
  • Voice Synthesizer :: Festival / ESpeak

Implementation Notes

Armbian + OrangePi Zero Installation

Enable analog soundcard

sudo armbian-config
# System > Hardware > [*] analog-codec

Software Dependencies

OS Packages

apt install mplayer espeak-ng

GPIO toolkit

# upstream:
#git clone https://github.com/orangepi-xunlong/wiringOP
# enhanced:
git clone https://github.com/Dejvino/wiringOP
cd wiringOP
./build clean
./build

Initialize GPIOs

# System Activity Indicator
PIN_SALIGHT=11
gpio mode $PIN_SALIGHT output

# Emergency Light system
PIN_ELIGHT=7
gpio mode $PIN_ELIGHT output

# PA system
PIN_PASOUND=5
gpio mode $PIN_PASOUND output

PA System

Text to Speech

## Festival
# reading
...
# to file
text2wave text.txt > wave.wav

## ESpeak
# voices:
ls /usr/lib/arm-linux-gnueabihf/espeak-data/voices/
# reading
espeak -f text.txt -p 40 -s 160 -v "en-us"
# to file
espeak -f text.txt -p 40 -s 160 -k15 -g 1 -w wave.wav
# using SSML (e.g.: https://www.xml.com/pub/a/2004/10/20/ssml.html)
espeak -f ssml.txt -m

Converting into a low-quality broadcast audio

sox infile.wav outfile.wav downsample echo 0.5 1 1 1

Playing a sound file

aplay file.wav
mplayer file.mp3

Emergency Light

Control Script

cat /usr/local/bin/emergency-light 
#!/bin/bash

PIN_ELIGHT=7

# init
gpio mode $PIN_ELIGHT output

# command
if [[ "$1" == "on" ]]; then
	gpio write $PIN_ELIGHT 1
elif [[ "$1" == "off" ]]; then
	gpio write $PIN_ELIGHT 0
elif [[ "$1" == "read" ]]; then
	gpio read $PIN_ELIGHT
else
	gpio toggle $PIN_ELIGHT
fi

System Activity Light

System Usage

uptime | head -n 1 | cut -f3 -d, | cut -f2 -d:

Daemon

cat /etc/systemd/system/system-activity-light.service
[Unit]
Description=System Activity Light Daemon

[Service]
ExecStart=/usr/sbin/system-activity-light-daemon

[Install]
WantedBy=multi-user.target

cat /usr/sbin/system-activity-light-daemon 
#!/bin/bash

DELAY=10000

while [[ true ]]; do
	ACTIVITY=2000
	TOP=`system-usage`
	if (( $(echo "$TOP > 1.0" | bc -l) )); then
		ACTIVITY=50
	elif (( $(echo "$TOP > 0.75" | bc -l) )); then
		ACTIVITY=100
	elif (( $(echo "$TOP > 0.5" | bc -l) )); then
		ACTIVITY=500
	elif (( $(echo "$TOP > 0.2" | bc -l) )); then
		ACTIVITY=1000
	fi
	echo $TOP
	system-activity-light blink $ACTIVITY $DELAY
done

sudo systemctl enable --now system-activity-light.service