Buzzer

Drive a buzzer or speaker using the PWM API.

Overview

This is a sample app which drives a buzzer or speaker using the PWM API.

The sample plays a short beep with 1108.73 ㎐ (music note D♭₆ [1]) for the time of a ⅛ music note [2] at boot time and offers the special shell command buzzer for playing other jingles or short songs.

Requirements

The sample requires a buzzer or speaker whose signal pin is connected to a pin driven by PWM. The buzzer or speaker must be defined in Devicetree using the pwm-buzzers compatible (part of the sample) and setting its node to the alias pwm-buzzer0. You will need to do something like this:

/ {
    aliases {
        pwm-buzzer0 = &pwm_buzzer0;
    };

    pwm_buzzers {
        compatible = "pwm-buzzers";
        status = "okay";

        pwm_buzzer0: pwm_buzzer0 {
            pwms = <&pwm0 1 PWM_HZ(880) PWM_POLARITY_NORMAL>;
            label = "PWM_BUZZER";
        };
    };
};

Note that a commonly used period value is 880 ㎐, twice the concert pitch frequency of 440 ㎐. See one of the following development boards:

Building and Running

  • On Maker Nano RP2040 board:

    west build -b cytron_maker_nano_rp2040 -p -S usb-console -d build/buzzer-cytron_maker_nano_rp2040 bridle/samples/buzzer
west flash -r uf2 -d build/buzzer-cytron_maker_nano_rp2040

  • On Maker Pi RP2040 board:

    west build -b cytron_maker_pi_rp2040 -p -S usb-console -d build/buzzer-cytron_maker_pi_rp2040 bridle/samples/buzzer
west flash -r uf2 -d build/buzzer-cytron_maker_pi_rp2040

Sample Output

(text in bold is a command input, text in angle brackets are keys to press)

[00:00:00.003,000] <inf> buzzersh: Buzzer shell is ready!


uart:~$ <Tab>
  bridle   buzzer   clear    device   devmem   gpio     help     history
  kernel   log      pwm      rem      resize   retval   shell

uart:~$ help
Please press the <Tab> button to see all available commands.
You can also use the <Tab> button to prompt or auto-complete all commands or its subcommands.
You can try to call commands with <-h> or <--help> parameter for more information.

Shell supports following meta-keys:
  Ctrl + (a key from: abcdefklnpuw)
  Alt  + (a key from: bf)
Please refer to shell documentation for more details.

Available commands:
  bridle   : Bridle commands.
  buzzer   : Buzzer related commands
  clear    : Clear screen.
  device   : Device commands
  devmem   : Read/write physical memory
             Usage:
             Read memory at address with optional width:
             devmem address [width]
             Write memory at address with mandatory width and value:
             devmem address <width> <value>
  gpio     : GPIO commands
  help     : Prints the help message.
  history  : Command history.
  kernel   : Kernel commands
  log      : Commands for controlling logger
  pwm      : PWM shell commands
  rem      : Ignore lines beginning with 'rem '
  resize   : Console gets terminal screen size or assumes default in case the
             readout fails. It must be executed after each terminal width change
             to ensure correct text display.
  retval   : Print return value of most recent command
  shell    : Useful, not Unix-like shell commands.

uart:~$ buzzer -h
buzzer - Buzzer related commands
Subcommands:
  info  :Get buzzer info
  beep  :Use buzzer to beep
  play  :Play one of predefined sounds

uart:~$ buzzer info
Warning: not yet implemented.

uart:~$ buzzer beep

uart:~$ buzzer play
play - Play one of predefined sounds
Subcommands:
  folksong   : Play the 'folksong' song
  xmastime   : Play the 'folksong' song
  funkytown  : Play the 'funkytown' song
  mario      : Play the 'mario' song
  golioth    : Play the 'golioth' song
  tiacsys    : Play the 'tiacsys' song

uart:~$ buzzer play folksong
uart:~$ buzzer play xmastime
uart:~$ buzzer play funkytown
uart:~$ buzzer play mario
uart:~$ buzzer play golioth
uart:~$ buzzer play tiacsys

References