- nRF52840
- SDK 15.3
- Segger Embedded Studio
I PWM a piezo buzzer (with a transistor) , using the PWM peripheral. The problem I encounter is that before I call the PWM function the power consumption is around 5uA, while after the PWM uninit() from the PWM event handler, the power consumption has increased to ~660uA. I checked that the driver is succesfully disabled, but I guess that the DMA is still on? If I go into shutdown mode with nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_STAY_IN_SYSOFF); the power consumption is reduced to 1.1uA as expected (mostly external hardware connected to the nRF52840).
So is there any way to reduce the power consumption after the PWM has been unitialized or is this not possible and should I use a different methode of PWM generation?
Code:
pwm.c
#include <stdbool.h>
#include <stdint.h>
#include "pwm.h"
#include "app_timer.h"
#include "nrf_gpio.h"
#include "boards.h"
#include "gpio-board.h"
#include "nrf_drv_pwm.h"
#include "nrf_drv_clock.h"
#include "nrf_log.h"
#include "app_util.h"
static nrf_drv_pwm_t m_pwm0 = NRF_DRV_PWM_INSTANCE(0);
void PWM_shutdown(void)
{
if(!nrfx_pwm_is_uninit(&m_pwm0))
{
nrf_drv_pwm_uninit(&m_pwm0);
}
}
static void PWM_handler(nrf_drv_pwm_evt_type_t event_type)
{
if (event_type == NRF_DRV_PWM_EVT_FINISHED)
{
nrf_drv_pwm_uninit(&m_pwm0);
NRF_LOG_INFO("PWM handler unint");
}
NRF_LOG_INFO("PWM handler %u/0x%02X, uninit %s", event_type, event_type, bool_to_str(nrfx_pwm_is_uninit(&m_pwm0)));
}
void PWM_event(uint8_t dutycycle, uint16_t frequency, uint16_t nRepeat)
{
uint32_t err;
static uint32_t regVal, topvalue;
// Ensure that the boost converter is enabled before attempting to sounds the buzzer.
#if 0
if(!GpioBoostConverterGet())
{
return;
}
#endif
if(frequency > 10000)
{
frequency = 10000;
}
if(frequency < 1000)
{
frequency = 1000;
}
topvalue = 1250000 / frequency;
if(dutycycle > 100)
{
dutycycle = 50;
}
// Calculate the PWM register value from the maximum top value and the given duty Cycle.
regVal = (topvalue * dutycycle) / 1000;
topvalue /= 10;
nrf_drv_pwm_config_t const config0 =
{
.output_pins =
{
BUZZER_PWM ,
NRF_DRV_PWM_PIN_NOT_USED,
NRF_DRV_PWM_PIN_NOT_USED,
NRF_DRV_PWM_PIN_NOT_USED,
},
.irq_priority = APP_IRQ_PRIORITY_LOWEST,
.base_clock = NRF_PWM_CLK_125kHz,
.count_mode = NRF_PWM_MODE_UP,
.top_value = topvalue,
.load_mode = NRF_PWM_LOAD_COMMON,
.step_mode = NRF_PWM_STEP_AUTO
};
// Check whether the pwm peripheral is already initialized.
bool pwmInit = nrfx_pwm_is_uninit(&m_pwm0);
NRF_LOG_INFO("PWM start, uninit=%s", bool_to_str(pwmInit));
if(!pwmInit)
{
nrf_drv_pwm_uninit(&m_pwm0);
NRF_LOG_INFO("PWM start unint");
}
err = nrf_drv_pwm_init(&m_pwm0, &config0, PWM_handler);
APP_ERROR_CHECK(err);
// This array cannot be allocated on stack (hence "static") and it must
// be in RAM (hence no "const", though its content is not changed).
static uint16_t /*const*/ seq_values[1];
seq_values[0] = regVal;
nrf_pwm_sequence_t const seq =
{
.values.p_common = seq_values,
.length = NRF_PWM_VALUES_LENGTH(seq_values),
.repeats = 0,
.end_delay = 0
};
(void)nrf_drv_pwm_simple_playback(&m_pwm0, &seq, nRepeat, NRF_DRV_PWM_FLAG_STOP);
}
pwm.h
/*!
* \file pwm.h
*
* \brief PWM for the buzzer.
*
*/
#ifndef __PWM_H__
#define __PWM_H__
#include <stdbool.h>
#include <stdint.h>
void PWM_event(uint8_t dutycycle, uint16_t frequency, uint16_t nRepeat);
void PWM_shutdown(void);
#endif // __PWM_H__
Addition to nrfx_pwm.c to check if the PWM state is equal to NRFX_DRV_STATE_UNINITIALIZED.
bool nrfx_pwm_is_uninit(nrfx_pwm_t const * const p_instance)
{
pwm_control_block_t * p_cb = &m_cb[p_instance->drv_inst_idx];
return (p_cb->state == NRFX_DRV_STATE_UNINITIALIZED) ? true : false;
}
