Example code for talking to a servo

[shampoo]

Hi

I am looking for some example code that shows best how to talk to a servo.. If there isn't any, any ideas which example project comes the closest ?

Thanks

J

[Sigurd]

Hi,

These servos are controlled by sending a Pulse width Modulation (PWM) signal. For the nRF51 the best starting point will be the PWM Library Example. It’s located in the folder

<SDK_InstallFolder>\examples\peripheral\pwm_library 

Try with a period of 20000L, and set the duty cycle to 5% and 10% for min and max servo position.

Code snippets:

app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(20000L, PWM_PIN);




while (app_pwm_channel_duty_set(&PWM1, 0, 10) == NRF_ERROR_BUSY);

[Sigurd]

Try something like this:

#include <stdbool.h>
#include <stdint.h>
#include "nrf.h"
#include "app_error.h"
#include "bsp.h"
#include "nrf_delay.h"
#include "app_pwm.h"

APP_PWM_INSTANCE(PWM1,1);                   // Create the instance "PWM1" using TIMER1.

int main(void)
{
    ret_code_t err_code;
    uint8_t SERVO_PIN = 4;

    /* 1-channel PWM, 50Hz, output on DK LED pins, 20ms period */
    app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(20000L, SERVO_PIN);

    /* Switch the polarity of the first channel. */
    pwm1_cfg.pin_polarity[0] = APP_PWM_POLARITY_ACTIVE_HIGH;

    /* Initialize and enable PWM. */
    err_code = app_pwm_init(&PWM1,&pwm1_cfg,NULL);
    APP_ERROR_CHECK(err_code);
    app_pwm_enable(&PWM1);

    uint8_t servo_pos_max = 10;
    uint8_t servo_pos_min = 5;
    while (true)
    {
        /* Set the duty cycle - keep trying until PWM is ready... */
        while (app_pwm_channel_duty_set(&PWM1, 0, servo_pos_max) == NRF_ERROR_BUSY);
        nrf_delay_ms(500);
        while (app_pwm_channel_duty_set(&PWM1, 0, servo_pos_min) == NRF_ERROR_BUSY);
        nrf_delay_ms(500);
     }

}


/** @} */