RE: voice output using PWM

awneil — Mon, 31 Dec 2018 10:29:38 GMT

How to properly post source code:

RE: voice output using PWM

air — Mon, 31 Dec 2018 08:02:57 GMT

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);
}
}

RE: voice output using PWM

air — Mon, 31 Dec 2018 07:42:36 GMT

There is something wrong.
I write 125L(125uS for 8K sampling) into the level register and PCM sampling data into the val register.

* @param [in] duty Duty cycle (0 - 100)

I wonder if the duty value can be applied to other values.
For example, 0 ~ 255 for 8bit sampling and 0 ~ 65535 for 16bit sampling.