Driving the Buzzer

Experiment Objective

In this experiment, you will learn how to drive the passive buzzer on the MicroROS-V2 control board. Through this example, you will master the configuration of the ESP32's LEDC (PWM) peripheral, as well as how to use PWM signals to drive the passive buzzer to produce sound and adjust its frequency.

Experiment Principle

1. Keywords

2. Technical Architecture

The program uses the ESP32's LEDC PWM controller to drive the passive buzzer. During initialization, the LEDC timer and channel are configured and GPIO47 is set as the PWM output. In the main loop, Beep_On_Time(500) is called every 1 second to make the buzzer sound for 500 ms and then stop automatically. A background task calls Beep_Handle() every 10 ms to manage the buzzer state and implement delayed automatic shutdown. Key files are located in ~/esp/base_samples/beep/, including main/main.c (main program entry), components/beep/beep.h (pin definitions and function declarations) and components/beep/beep.c (buzzer driver implementation).

Experiment Steps

1. Hardware Preparation

2. Prerequisites

1. ESP32-IDF development environment set up

2. MicroROS-V2 control board connected to the PC via USB

3. Confirm the buzzer on the control board is functioning properly

3. Compile and Flash

​x

cd ~/esp/base_samples/beep
source ~/esp/esp-idf/export.sh
idf.py build flash monitor

4. How to Stop

Press Ctrl+] in the terminal to exit the serial monitor.

Experiment Result

After compiling and flashing successfully, the serial monitor will output:

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hello yahboom
I (xxx) BEEP: Start Beep_Task with core:1
I (xxx) MAIN: Nice to meet you!

At the same time, the buzzer on the control board beeps once every 1 second, each time lasting 500 milliseconds, producing a clear "beep" sound.

Code Explanation

Source code paths:

• Firmware source code: ~/esp/base_samples/beep/main/main.c

• Buzzer driver: ~/esp/base_samples/beep/components/beep/beep.h, beep.c

1. Main Program Logic

main/main.c is the program entry, and the flow is as follows:

1. Print the startup message "hello yahboom" and a welcome log

2. Call Beep_Init() to initialize the buzzer PWM

3. Wait 1 second

4. Enter the main loop, calling Beep_On_Time(500) every 1 second to make the buzzer sound for 500 ms and then stop automatically

2. Key Components

components/beep/beep.h — pin definitions and function declarations:

Parameter definition file: ~/esp/base_samples/beep/components/beep/beep.h

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// Buzzer GPIO pin (schematic: Buzzer -> U6-24 -> GPIO47)
#define BEEP_GPIO               47

// Passive buzzer default parameters
#define BEEP_DEFAULT_FREQ_HZ    2000     // Default frequency 2 KHz
#define BEEP_DEFAULT_DUTY_PCT   50       // Default duty cycle 50%

#define BEEP_STATE_OFF       0           // Off state
#define BEEP_STATE_ON_ALWAYS 1           // Always-on state
#define BEEP_STATE_ON_DELAY  2           // Delayed off state

components/beep/beep.c — buzzer driver implementation, with the following core functions:

PWM initialization parameters:

The buzzer uses the ESP32's LEDC PWM controller, configured as follows:

Source file: ~/esp/base_samples/beep/components/beep/beep.c

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// LEDC timer configuration
ledc_timer_config_t timer_conf = {
    .speed_mode      = LEDC_LOW_SPEED_MODE,
    .duty_resolution = LEDC_TIMER_10_BIT,     // 10-bit resolution (0~1023)
    .timer_num       = LEDC_TIMER_0,
    .freq_hz         = BEEP_DEFAULT_FREQ_HZ,  // Default 2 KHz
    .clk_cfg         = LEDC_AUTO_CLK
};

// LEDC channel configuration
ledc_channel_config_t channel_conf = {
    .gpio_num   = BEEP_GPIO,                  // GPIO47
    .speed_mode = LEDC_LOW_SPEED_MODE,
    .channel    = LEDC_CHANNEL_0,
    .intr_type  = LEDC_INTR_DISABLE,
    .timer_sel  = LEDC_TIMER_0,
    .duty       = 0,
    .hpoint     = 0
};

Frequency and duty cycle control:

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// Start PWM output
Beep_PWM_Start(freq_hz, duty_percent);  // Frequency range limited to 100~10000 Hz
// Stop PWM output (set duty cycle to 0)
Beep_PWM_Stop();

Delayed shutdown working mechanism:

After Beep_On_Time(500) is called, the buzzer state switches to BEEP_STATE_ON_DELAY. The background task Beep_Task calls Beep_Handle() every 10 ms, decrementing the beep_on_time counter. When the count reaches zero, Beep_Off() is called automatically to turn off the buzzer.

Common Problems