Buzzer

Overview

The AlphaBot V2 includes a passive buzzer, which is a simple audio output device that can generate tones, beeps, and melodies when controlled by a microcontroller (like Arduino or Raspberry Pi).

Key Feature

• Passive Buzzer (Requires External Signal)
  • Unlike an active buzzer (which has an internal oscillator and produces sound with just a DC voltage), a passive buzzer needs a PWM (Pulse Width Modulation) signal to generate different tones.
  • This allows for variable frequency control, enabling musical notes and custom sound effects. Connected to a Digital/PWM
• Connected to a Digital/PWM Pin
  • Typically wired to a PWM-capable pin.
• Common Uses in Robotics
  • Alerts & Notifications (e.g., obstacle detection, low battery).
  • Simple Melodies (e.g., startup sound, error beeps).
  • User Feedback (e.g., button press confirmation).

Working

• PCF8574 I/O Expander
  • The PCF8574 is an 8-bit I/O expander that communicates via I²C (Arduino’s Wire library).
• Buzzer Control Logic
  • The buzzer is controlled by bit manipulation of the PCF8574's output register.
  • beep_on → Sets a specific bit (0xDF mask) to activate the buzzer.
  • beep_off → Clears the bit (0x20 mask) to deactivate the buzzer.
• PCF8574Write(byte data)
  • Sends a byte (data) to the PCF8574 to update its output pins.
• PCF8574Read()
  • Reads the current state of the PCF8574's input/output pins. Returns a byte representing the pin states.
• beep_on = PCF8574Write(0xDF & PCF8574Read())
  • Masks the current state with 0xDF (binary 11011111), clearing the buzzer-control bit.
• beep_off = PCF8574Write(0x20 | PCF8574Read())
  • Masks the current state with 0x20 (binary 00100000), setting the buzzer-control bit.