I'm trying to get some sound out of a piezo buzzer using the PWM library here:
github.com/.../nrf51-pwm-library
My buzzer has a resonant frequency of 2,730Hz. The buzzer doesn't have its own driver, I need to generate the wave for it. What changes do I need to make to main_sin.c to get that frequency?
Here's what I've tried so far.
int main(void)
{
uint32_t counter = 0;
nrf_pwm_config_t pwm_config = PWM_DEFAULT_CONFIG;
pwm_config.mode = PWM_MODE_BUZZER_64; // Was PWM_MODE_LED_100
pwm_config.num_channels = 1; // Was 3
// One channel only, on pin 14
pwm_config.gpio_num[0] = 14; // Was 8
// pwm_config.gpio_num[1] = 8;
// pwm_config.gpio_num[2] = 10;
// Initialize the PWM library
nrf_pwm_init(&pwm_config);
while (true)
{
// Update the 3 outputs with out of phase sine waves
nrf_pwm_set_value(0, sin_table[counter]);
// nrf_pwm_set_value(1, sin_table[(counter + 33) % 100]);
// nrf_pwm_set_value(2, sin_table[(counter + 66) % 100]);
counter = (counter + 1) % 100;
// Add a delay to control the speed of the sine wave
// 125 kHz is one wave every 0.000008s or 0.008ms or 8us, so why is this 8000us?
// nrf_delay_us(8000);
// If 8000us gets us 125kHz, then 366,300 should get us 2730Hz.
nrf_delay_us(366300);
}
}
As the comments above show, I'm confused about how this delay relates to the PWM frequency.
I'd also like to be executing other code while the buzzer is sounding and thought that PPI made this possible. So why the while() loop here at all?
