reterminal-dm4/chromium-setup/BUZZER-CONTROL-SIMPLE.md

Simple Buzzer Control Guide - reTerminal DM4

Overview

The reTerminal DM4 has a built-in buzzer that can be controlled for alerts and notifications. The buzzer is located at the bottom right corner of the screen.

Quick Start

Turn Buzzer ON

echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness

Turn Buzzer OFF

echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness

Check Buzzer Status

cat /sys/class/leds/usr-buzzer/brightness

• 0 = OFF
• 1 or 255 = ON

---

Basic Control Methods

Method 1: Command Line (Simple)

Single Beep (0.2 seconds):

echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness
sleep 0.2
echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness

Double Beep:

for i in 1 2; do
    echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness
    sleep 0.1
    echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness
    sleep 0.1
done

Long Beep (1 second):

echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness
sleep 1
echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness

Method 2: Python Script

Simple Python Control:

import subprocess
import time

BUZZER_PATH = '/sys/class/leds/usr-buzzer/brightness'

def buzzer_on():
    """Turn buzzer ON"""
    subprocess.run(['sudo', 'tee', BUZZER_PATH], input='1', text=True)

def buzzer_off():
    """Turn buzzer OFF"""
    subprocess.run(['sudo', 'tee', BUZZER_PATH], input='0', text=True)

def beep(duration=0.2):
    """Play a beep for specified duration (in seconds)"""
    buzzer_on()
    time.sleep(duration)
    buzzer_off()

# Usage
beep(0.2)        # Short beep
beep(0.5)        # Medium beep
beep(1.0)        # Long beep

Blinking Pattern:

def beep_pattern(count=3, on_time=0.1, off_time=0.1):
    """Blink buzzer multiple times"""
    for _ in range(count):
        buzzer_on()
        time.sleep(on_time)
        buzzer_off()
        time.sleep(off_time)

# Usage
beep_pattern(3, 0.1, 0.1)  # 3 quick beeps

Method 3: Bash Function

Add to your ~/.bashrc:

buzzer() {
    local action=$1
    local duration=${2:-0.2}
    local BUZZER='/sys/class/leds/usr-buzzer/brightness'
    
    case $action in
        on)
            echo 1 | sudo tee $BUZZER > /dev/null
            ;;
        off)
            echo 0 | sudo tee $BUZZER > /dev/null
            ;;
        beep)
            echo 1 | sudo tee $BUZZER > /dev/null
            sleep $duration
            echo 0 | sudo tee $BUZZER > /dev/null
            ;;
        *)
            echo "Usage: buzzer {on|off|beep [duration]}"
            ;;
    esac
}

Then use:

buzzer on           # Turn on
buzzer off          # Turn off
buzzer beep 0.2     # Beep for 0.2 seconds
buzzer beep 0.5     # Beep for 0.5 seconds

---

Common Patterns

Success Alert (2 short beeps)

for i in 1 2; do
    echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness
    sleep 0.1
    echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness
    sleep 0.1
done

Error Alert (3 fast beeps)

for i in 1 2 3; do
    echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness
    sleep 0.05
    echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness
    sleep 0.05
done

Warning Alert (1 long beep)

echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness
sleep 0.5
echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness

Notification (1 short beep)

echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness
sleep 0.2
echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness

---

Using the Test Script

A test script is available at /tmp/test_buzzer.sh on the device:

# Run the test script
ssh guard "/tmp/test_buzzer.sh"

Or copy and run locally:

scp guard:/tmp/test_buzzer.sh ./
chmod +x test_buzzer.sh
./test_buzzer.sh

---

Important Notes

1. Requires sudo: All buzzer control commands require root privileges
2. Simple on/off: The buzzer can only be turned ON or OFF - no volume or frequency control
3. Location: Bottom right corner of the screen
4. Use case: Alerts, notifications, system events

---

Troubleshooting

Buzzer Not Working

1. Check device exists:

   ls -la /sys/class/leds/usr-buzzer/
   

2. Test manually:

   echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness
   # Wait a moment - you should hear the buzzer
   echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness
   

3. Check permissions:

   ls -la /sys/class/leds/usr-buzzer/brightness
   # Should show: -rw-r--r-- (requires sudo to write)
   

4. Verify current state:

   cat /sys/class/leds/usr-buzzer/brightness
   # 0 = off, 1 or 255 = on
   

No Sound from Buzzer

• Check if buzzer is physically present and working
• Verify the device is powered on
• Try a longer duration (e.g., sleep 1 instead of sleep 0.2)
• Check kernel messages: dmesg | grep -i buzzer

---

Examples

Example 1: Simple Alert Function

#!/bin/bash
alert() {
    echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness
    sleep 0.3
    echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness
}

# Use it
alert

Example 2: Python Notification System

import subprocess
import time

def notify(message_type):
    BUZZER = '/sys/class/leds/usr-buzzer/brightness'
    
    patterns = {
        'info': (1, 0.1),      # 1 beep, 0.1s
        'success': (2, 0.1),   # 2 beeps, 0.1s each
        'error': (3, 0.05),    # 3 fast beeps
        'warning': (1, 0.5),   # 1 long beep
    }
    
    count, duration = patterns.get(message_type, (1, 0.2))
    
    for _ in range(count):
        subprocess.run(['sudo', 'tee', BUZZER], input='1', text=True)
        time.sleep(duration)
        subprocess.run(['sudo', 'tee', BUZZER], input='0', text=True)
        time.sleep(0.1)

# Usage
notify('success')  # 2 short beeps
notify('error')    # 3 fast beeps

---

Quick Reference

Action	Command
Turn ON	echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness
Turn OFF	echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness
Check Status	cat /sys/class/leds/usr-buzzer/brightness
Single Beep	echo 1 | sudo tee /sys/class/leds/usr-buzzer/brightness && sleep 0.2 && echo 0 | sudo tee /sys/class/leds/usr-buzzer/brightness

---

Related Documentation

• BUZZER-TEST-GUIDE.md - Detailed testing guide
• FLASK-BUZZER-CONTROL.md - Flask web API for buzzer control
• starwars_buzzer.sh - Star Wars theme example script

---

Summary

The buzzer is simple to control:

1. Path: /sys/class/leds/usr-buzzer/brightness
2. Values: 0 = OFF, 1 = ON
3. Requires: sudo privileges
4. Control: Write 1 to turn on, 0 to turn off

That's it! Simple and straightforward.