Piezo Buzzer PWM Aries v3.0

Theory

A piezoelectric buzzer converts an electrical signal into mechanical vibration, producing an audible sound. In this system, the electrical signal is generated using Pulse-Width Modulation (PWM).

The PWM frequency determines the pitch of the generated sound. Higher frequencies produce higher-pitched tones, while lower frequencies produce lower-pitched tones.

A duty cycle of approximately 50% produces a balanced square wave suitable for pure buzzer tones.

PWM Tone Generation

Frequency and Pitch

The relationship between frequency and pitch can be expressed as:

Higher Frequency
       ↓
Higher Pitch

Lower Frequency
       ↓
Lower Pitch
                

Duty Cycle

The duty cycle represents the percentage of time that the PWM signal remains HIGH during one complete cycle. A 50% duty cycle provides an approximately equal HIGH and LOW duration.

PWM Duty Cycle = 50%

HIGH  ──────
            │
LOW   ──────
            │
            └── Repeated continuously
                

Architecture

The Piezo Buzzer PWM system consists of the embedded firmware, Aries v3.0 RISC-V SoC, PWM controller, GPIO interface, and piezoelectric buzzer output model.

System Components

• Aries v3.0 RISC-V Microcontroller SoC
• GPIO0 interface
• PWM frequency generator
• PWM duty-cycle controller
• Piezoelectric transducer model
• Audio output model
• Integrated simulator and waveform viewer

Source Code

Example firmware for configuring the Piezo Buzzer PWM peripheral.

Register Definitions

#define GPIO0_MODE  0x40000000
#define GPIO0_IN    0x40000004
#define GPIO0_OUT   0x40000008

#define PWM_FREQ    0x40000820
#define PWM_DUTY    0x40000824
                

GPIO Configuration

// Configure GPIO0 bit 0 as buzzer output

WRITE_REGISTER(GPIO0_MODE, 0x01);
                

PWM Configuration

// Configure 50% duty cycle
WRITE_REGISTER(PWM_DUTY, 50);

// Generate A4 tone
WRITE_REGISTER(PWM_FREQ, 440);
                

Firmware Entrypoint

void fw_main(void)
{
    // Configure GPIO0 bit 0 as buzzer output
    WRITE_REGISTER(0x40000000, 0x01);

    // Configure 50% duty cycle
    WRITE_REGISTER(0x40000824, 50);

    // Generate 440 Hz A4 tone
    WRITE_REGISTER(0x40000820, 440);

    while (1)
    {
        // PWM hardware continuously drives the buzzer
    }
}
                

Pinout

GPIO and PWM register mapping for the Piezo Buzzer PWM output.

GPIO0 - Buzzer Output

Register Addresses

Examples

Example exercises for the Piezo Buzzer PWM system.

• Generate a single buzzer tone
• Generate C4 through C5 musical notes
• Generate an ascending musical sequence
• Generate an alarm sound
• Experiment with PWM frequency
• Experiment with PWM duty cycle
• Create a custom melody
• Control note duration
• Observe PWM waveforms

Musical Notes