voice output using PWM

[air]

 Hello,

I'm trying to play voice using PWM in nRF51822.

I've already experienced this using other MCU before.

So. I'm trying.

Voice source data is 8bit / 8K / mono PCM sampling data.

I call below code according to 8KHz frequency.

I write the above PCM sampling data value to below level register.

The val register value is a fixed value of 50.

At the test level, I don't execute any other code, but only this code.

And the below code is used for buzzer playback now.

I don't know what's wrong.

Could anybody let me know what's wrong or some tip?

 Thanks and happy new year.

*****************************************************************************************

// for sound level

err_code = app_pwm_uninit(&PWM_BUZZER);
// NRF_LOG_RAW_INFO("pwm-buzzer uninit error : %d\r\n", err_code);
APP_ERROR_CHECK(err_code);

app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(level, BUZZER_PIN);
pwm1_cfg.pin_polarity[0] = APP_PWM_POLARITY_ACTIVE_HIGH;

err_code = app_pwm_init(&PWM_BUZZER, &pwm1_cfg, NULL); // callback_pwmBuz);
// NRF_LOG_RAW_INFO("pwm-buzzer init error : %d\r\n", err_code);
APP_ERROR_CHECK(err_code);

app_pwm_enable(&PWM_BUZZER);
// NRF_LOG_RAW_INFO("pwm-buzzer enable\r\n");

// for sound strength
while(app_pwm_channel_duty_set(&PWM_BUZZER, 0, val) == NRF_ERROR_BUSY);

*****************************************************************************************

[air]

I modified the library as shown below and confirmed that the voice was output.

But the quality is too low.

I have already commercialized it in this way.

Of course I have to optimize the hardware, but I do not know why.

****************************************************************************************************************

APP_PWM_INSTANCE(PWM1,1); // Create the instance "PWM1" using TIMER1.

static volatile bool ready_flag; // A flag indicating PWM status.

uint16_t voiceData = 0;

const unsigned char hexData[8253] = {

// 8bit/8K PCM sampling data

}

void pwm_ready_callback(uint32_t pwm_id) // PWM callback function
{
ready_flag = true;

int main(void)
{
  ret_code_t err_code;

  while (true)
  {
    /* 2-channel PWM, 200Hz, output on DK LED pins. */
    // app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_2CH(5000L, BSP_LED_0, BSP_LED_1);
    app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(125L, 13);

    /* Switch the polarity of the second channel. */
    // pwm1_cfg.pin_polarity[1] = APP_PWM_POLARITY_ACTIVE_HIGH;
    pwm1_cfg.pin_polarity[0] = 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);

    // for speaker DC-DC enable
    nrf_gpio_pin_set(16);
    nrf_gpio_cfg_output(16);
    nrf_delay_ms(100);

 
    for (uint16_t i = 0; i < 8253; i++)
    {
      ready_flag = false;

      // voiceData = (hexData[i] * 100) / 0xff;
      voiceData = hexData[i] / 2;

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

      /* ... or wait for callback. */
      while (!ready_flag);
      // APP_ERROR_CHECK(app_pwm_channel_duty_set(&PWM1, 1, value));
      // nrf_delay_ms(25);
    }

    // for speaker DC-DC disable
    app_pwm_disable(&PWM1);
    nrf_gpio_pin_clear(13);
    nrf_gpio_cfg_output(13);
    nrf_delay_ms(2000);
  }
}

[awneil]

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