Hi,
I have a piezo buzzer connected to pin 14 on a Nordic nRF51822. Here's some code I use to drive it, based on the Nordic PWM library here: github.com/.../nrf51-pwm-library.
This code used to work! It doesn't any longer and I've been staring at it for hours trying to figure out why. A scope attached to pin 14 on the Nordic shows no changes in voltage at all. Since this was last working, I've bumped SDK versions twice, but I can't see that that would have much effect on it. Am currently on SDK 6.1.0 and SD 7.0.0.
buzzer.h:
#define PWM_TIMER NRF_TIMER2
#define PWM_IRQn TIMER2_IRQn
#define PWM_IRQHandler TIMER2_IRQHandler
#define PWM_IRQ_PRIORITY (3)
#define PWM_PPI_CHANNEL_0 (0)
#define PWM_PPI_CHANNEL_1 (1)
#define PWM_GPIOTE_CHANNEL_0 (2)
void buzzer_init(void);
void buzzer_ble_connect(void);
void buzzer_ble_disconnect(void);
buzzer.c:
#include <stdbool.h>
#include "nordic_common.h"
#include "nrf.h"
#include "nrf_gpio.h"
#include "nrf_gpiote.h"
#include "nrf_delay.h"
#include "nrf_sdm.h"
#include "app_timer.h"
#include "buzzer.h"
#include "bike_tracker_201402.h"
static uint32_t m_pwm_next_value;
static uint32_t m_pwm_io_ch;
static uint32_t m_pwm_running;
static uint32_t m_pwm_max_value;
static app_timer_id_t m_buzzer_timeout_timer_id;
static bool m_buzzer_timed_out = false;
// Sine wave
const uint8_t sin_table[] = {0,0,1,2,4,6,9,12,16,20,24,29,35,40,46,53,59,66,74,81,88,96,104,112,120,128,136,144,152,160,168,175,182,190,197,203,210,216,221,227,
232,236,240,244,247,250,252,254,255,255,255,255,255,254,252,250,247,244,240,236,232,227,221,216,210,203,197,190,182,175,168,160,152,144,136,128,120,112,104,
96,88,81,74,66,59,53,46,40,35,29,24,20,16,12,9,6,4,2,1,0};
static void buzzer_timeout_handler(void * p_context)
{
UNUSED_PARAMETER(p_context);
m_buzzer_timed_out = true;
}
static void nrf_pwm_set_value(uint32_t pwm_value)
{
m_pwm_next_value = pwm_value;
PWM_TIMER->EVENTS_COMPARE[3] = 0;
PWM_TIMER->SHORTS = TIMER_SHORTS_COMPARE3_CLEAR_Msk | TIMER_SHORTS_COMPARE3_STOP_Msk;
if ((PWM_TIMER->INTENSET & TIMER_INTENSET_COMPARE3_Msk) == 0)
{
PWM_TIMER->TASKS_STOP = 1;
PWM_TIMER->INTENSET = TIMER_INTENSET_COMPARE3_Msk;
}
PWM_TIMER->TASKS_START = 1;
}
void PWM_IRQHandler(void)
{
PWM_TIMER->EVENTS_COMPARE[3] = 0;
PWM_TIMER->INTENCLR = 0xFFFFFFFF;
if (m_pwm_next_value == 0)
{
nrf_gpiote_unconfig(PWM_GPIOTE_CHANNEL_0);
nrf_gpio_pin_write(m_pwm_io_ch, 0);
m_pwm_running = 0;
}
else if (m_pwm_next_value >= m_pwm_max_value)
{
nrf_gpiote_unconfig(PWM_GPIOTE_CHANNEL_0);
nrf_gpio_pin_write(m_pwm_io_ch, 1);
m_pwm_running = 0;
}
else
{
PWM_TIMER->CC[0] = m_pwm_next_value * 2;
if (!m_pwm_running)
{
nrf_gpiote_task_config(PWM_GPIOTE_CHANNEL_0, m_pwm_io_ch, NRF_GPIOTE_POLARITY_TOGGLE, NRF_GPIOTE_INITIAL_VALUE_HIGH);
m_pwm_running = 1;
}
}
PWM_TIMER->SHORTS = TIMER_SHORTS_COMPARE3_CLEAR_Msk;
PWM_TIMER->TASKS_START = 1;
}
void buzzer_init(void)
{
uint32_t err_code;
nrf_gpio_cfg_output(PIN_BUZZER_ON);
m_pwm_io_ch = (uint32_t)PIN_BUZZER_ON;
m_pwm_running = 0;
// Create timer once, start and stop the same timer multiple times.
err_code = app_timer_create(&m_buzzer_timeout_timer_id, APP_TIMER_MODE_SINGLE_SHOT, buzzer_timeout_handler);
APP_ERROR_CHECK(err_code);
PWM_TIMER->PRESCALER = 0;
PWM_TIMER->TASKS_CLEAR = 1;
PWM_TIMER->BITMODE = TIMER_BITMODE_BITMODE_16Bit;
PWM_TIMER->MODE = TIMER_MODE_MODE_Timer;
PWM_TIMER->SHORTS = TIMER_SHORTS_COMPARE3_CLEAR_Msk;
PWM_TIMER->EVENTS_COMPARE[0] = PWM_TIMER->EVENTS_COMPARE[1] = PWM_TIMER->EVENTS_COMPARE[2] = PWM_TIMER->EVENTS_COMPARE[3] = 0;
sd_ppi_channel_assign(PWM_PPI_CHANNEL_0, &PWM_TIMER->EVENTS_COMPARE[0], &NRF_GPIOTE->TASKS_OUT[PWM_GPIOTE_CHANNEL_0]);
sd_ppi_channel_enable_set(1 << PWM_PPI_CHANNEL_0);
// Strangely, omitting these two lines makes for a different, lower tone. No idea why.
sd_ppi_channel_assign(PWM_PPI_CHANNEL_1, &PWM_TIMER->EVENTS_COMPARE[3], &NRF_GPIOTE->TASKS_OUT[PWM_GPIOTE_CHANNEL_0]);
sd_ppi_channel_enable_set(1 << PWM_PPI_CHANNEL_1);
sd_nvic_SetPriority(PWM_IRQn, PWM_IRQ_PRIORITY | 0x01);
sd_nvic_EnableIRQ(PWM_IRQn);
}
static void buzzer_on(uint32_t frequency, uint32_t duration)
{
uint32_t err_code;
uint32_t counter = 0;
// Only valid if the prescaler is 0:
m_pwm_max_value = (16 * 1000 * 1000 / (2 * frequency));
PWM_TIMER->CC[3] = m_pwm_max_value * 2;
PWM_TIMER->TASKS_START = 1;
// Start timeout timer again.
m_buzzer_timed_out = false;
err_code = app_timer_start(m_buzzer_timeout_timer_id, APP_TIMER_TICKS(duration, 0), NULL);
APP_ERROR_CHECK(err_code);
while (!m_buzzer_timed_out)
{
nrf_pwm_set_value(sin_table[counter]);
counter = (counter + 1) % 100;
// Add a delay to control the speed of the sine wave. Messing with this alters the sound a
// bit but not in an interesting way.
nrf_delay_us(8000);
}
PWM_TIMER->TASKS_STOP = 1;
err_code = app_timer_stop(m_buzzer_timeout_timer_id);
APP_ERROR_CHECK(err_code);
}
void buzzer_ble_connect(void)
{
buzzer_on(440, 60);
buzzer_on(880, 180);
nrf_delay_ms(1000);
}
void buzzer_ble_disconnect(void)
{
buzzer_on(880, 60);
buzzer_on(440, 180);
nrf_delay_ms(1000);
}
main.c:
int main(void)
{
// Test buzzer.
APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_MAX_TIMERS, APP_TIMER_OP_QUEUE_SIZE, false);
buzzer_init();
for (;;) {
buzzer_ble_connect();
buzzer_ble_disconnect();
}
}
Any help would be greatly appreciated as always. Thanks in advance.
