Hi
I'm using this simple_pwm code to drive my speaker, I use this as a buzzer but I want to change the frequency.
In this code ".base_clock = NRF_PWM_CLK_125kHz", the clock can only go as low as 125kHz, I want to have like 2kHz frequency.
I don't know how I can achieve it, please correct me if I was wrong.
thanks,
Cindy
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/** @file
* @defgroup pwm_example_main main.c
* @{
* @ingroup pwm_example
*
* @brief PWM Example Application main file.
*
* This file contains the source code for a sample application using PWM.
*/
#include <stdio.h>
#include <string.h>
#include "nrf_drv_pwm.h"
#include "app_util_platform.h"
#include "app_error.h"
#include "boards.h"
#include "bsp.h"
#include "nrf_drv_clock.h"
#include "nrf_delay.h"
#define OUTPUT_PIN 8
static nrf_drv_pwm_t m_pwm0 = NRF_DRV_PWM_INSTANCE(0);
// Declare variables holding PWM sequence values. In this example only one channel is used
nrf_pwm_values_individual_t seq_values[] = {0, 0, 0, 0};
nrf_pwm_sequence_t const seq =
{
.values.p_individual = seq_values,
.length = NRF_PWM_VALUES_LENGTH(seq_values),
.repeats = 0,
.end_delay = 0
};
// Set duty cycle between 0 and 100%
void pwm_update_duty_cycle(uint8_t duty_cycle)
{
duty_cycle = 70;
// Check if value is outside of range. If so, set to 100%
if(duty_cycle >= 100)
{
seq_values->channel_0 = 100;
}
else
{
seq_values->channel_0 = duty_cycle;
}
nrf_drv_pwm_simple_playback(&m_pwm0, &seq, 1, NRF_DRV_PWM_FLAG_LOOP);
}
static void pwm_init(void)
{
nrf_drv_pwm_config_t const config0 =
{
.output_pins =
{
OUTPUT_PIN, // channel 0
NRF_DRV_PWM_PIN_NOT_USED, // channel 1
NRF_DRV_PWM_PIN_NOT_USED, // channel 2
NRF_DRV_PWM_PIN_NOT_USED, // channel 3
},
.irq_priority = APP_IRQ_PRIORITY_LOWEST,
.base_clock = NRF_PWM_CLK_125kHz,
.count_mode = NRF_PWM_MODE_UP,
.top_value = 100,
.load_mode = NRF_PWM_LOAD_INDIVIDUAL,
.step_mode = NRF_PWM_STEP_AUTO
};
// Init PWM without error handler
APP_ERROR_CHECK(nrf_drv_pwm_init(&m_pwm0, &config0, NULL));
}
int main(void)
{
// Start clock for accurate frequencies
NRF_CLOCK->TASKS_HFCLKSTART = 1;
// Wait for clock to start
while(NRF_CLOCK->EVENTS_HFCLKSTARTED == 0)
;
pwm_init();
for (;;)
{
for(int i = 0; i <= 100; i++)
{
nrf_delay_ms(10);
pwm_update_duty_cycle(i);
}
}
}
/** @} */
