I'm trying to send a low signal to the buzzer when I'm not using pwm.

[schosdas]

Hello

I am developing devices including nrf52832 and 3.3v buzzer.
However, the buzzer in this device is very hot and the battery is running out quickly.

Now I know that this buzzer is still HIGH state even when it's not in use.  So, to solve this problem, I tried to output the LOW signal on the pins of the buzzer when the buzzer is not used.

However, the buzzer still does not change at the HIGH signal.

This is a my pwm code and circuit diagram about buzzer.

void pwm_play_buzzer_duration(uint32_t duration) //button buzzer
{
    uint8_t i;
    uint32_t duty = 50;

    NRF_LOG_INFO("pwm_play_buzzer_duration =>");    
    ready_flag = false;

    //Set the duty cycle - keep trying until PWM is ready... 
    while (app_pwm_channel_duty_set(&PWM1, 0, duty) == NRF_ERROR_BUSY);

    // ... or wait for callback. 
    //while (!ready_flag);
    //APP_ERROR_CHECK(app_pwm_channel_duty_set(&PWM1, 1, duty));
    nrf_delay_ms(duration);
    app_pwm_disable(&PWM1);
}


void pwm_ready_callback(uint32_t pwm_id)    // PWM callback function
{
    NRF_LOG_INFO("pwm_ready_callback =>");
    ready_flag = true;
}

/*
 init, Once executed
 */
//buzzer PWM initializing
void pwm_init(void) 
{
    ret_code_t err_code;

    /* 1-channel PWM, 200Hz, output on DK LED pins. */
    app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(1500, BUZZER_PIN); 
    
    /* Switch the polarity of the second channel. */
    pwm1_cfg.pin_polarity[1] = APP_PWM_POLARITY_ACTIVE_HIGH;
    
    /* Initialize and enable PWM. */
    err_code = app_pwm_init(&PWM1,&pwm1_cfg,pwm_ready_callback);
    APP_ERROR_CHECK(err_code);
    app_pwm_enable(&PWM1);
}


/*
 pwm_change_frequency,Can be executed multiple times
*/
void pwm_change_frequency(uint16_t period_us) // different sound
{
    ret_code_t err_code;

    app_pwm_disable(&PWM1); //disable PWM for change PWM
    app_pwm_uninit(&PWM1); //uninitializing a PWM

    /* 1-channel PWM, 200Hz, output on DK LED pins. */
    app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(period_us, BUZZER_PIN); //original 5000L
    
    /* Switch the polarity of the second channel. */
    pwm1_cfg.pin_polarity[1] = APP_PWM_POLARITY_ACTIVE_HIGH;
    
    /* Initialize and enable PWM. */
    err_code = app_pwm_init(&PWM1,&pwm1_cfg,pwm_ready_callback);
    APP_ERROR_CHECK(err_code);
    app_pwm_enable(&PWM1);
}


void gpio_init(void)
{
  nrf_gpio_cfg_output(BUZZER_PIN); //pin25
  nrf_gpio_pin_clear(BUZZER_PIN);
}


static void do_play_buzzer(void)
{
  pwm_play_buzzer_duration(200); //buzzer play time
  app_pwm_enable(&PWM1);

  nrf_gpio_pin_clear(BUZZER_PIN); //buzzer LOW signal
}

static void do_play_buzzer_2(void) //double play buzzer test
{
  pwm_play_buzzer_duration(200); //buzzer play time
  app_pwm_enable(&PWM1);
  nrf_delay_ms(200);
  pwm_play_buzzer_duration(200); //buzzer play time
  app_pwm_enable(&PWM1);

  nrf_gpio_pin_clear(BUZZER_PIN); //buzzer LOW signal
}

Can I know about this problem?

Thank you.

[Edvin]

My electronics diagram reading is a bit rusty. What is the voltage at 2 when the nRF sets the output pin to low, and what is the volate at 2 when the nRF sets the output pin to high?

Basically, how does this behave? What is it? Is it an NMOSFET?

If I remember correctly, when you set the pin from the nRF to low, the transistor is open, right? So the voltage at 2 should be VDD (3.3V)? Have you tried to measure the voltage at the nRF to check whether it is set to low or not?

BR,

Edvin

[hmolesworth]

I don't see the background port pin setting function you have being called; try adding this before running, it might fix your issue:

  gpio_init();

[schosdas]

Oh, I'm sorry.
The code above omitted the main(), but the gpio_init() is in the main().

Thank you.

[hmolesworth]

Yes, but where - ie in what order?

"To ensure correct behaviour in the PWM module, the pins used by the PWM module must be configured in the GPIO peripheral as described in Table 118: Recommended GPIO configuration before starting PWM generation on page 504 before enabling the PWM module. The pins' idle state is defined by the OUT registers in the GPIO module. This is to ensure that the pins used by the PWM module are driven correctly, if PWM generation is stopped through a STOP task, the PWM module itself is temporarily disabled, or the device temporarily enters System OFF. This configuration must be retained in the GPIO for the selected IOs as long as the PWM module is supposed to be connected to an external PWM circuit"