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);

[shampoo]

Hi

I am using the following code with no luck at all.. The servo refuses to move. I am 100% certain the hardware connections are correct and the servo does work.. Any ideas ? Here is my code:

BTW, I am using SDK 11.

int init_servo2(void)
{
	ret_code_t err_code;

	/* 2-channel PWM, 200Hz, output on DK LED pins. */
	app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(20000L, SERVO_PIN);

	/* Switch the polarity of the second channel. */
	pwm1_cfg.pin_polarity[1] = APP_PWM_POLARITY_ACTIVE_HIGH;

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

	uint32_t value;
	while(true)
	{
		for (uint8_t i = 0; i < 40; ++i)
		{
			value = (i < 20) ? (i * 5) : (100 - (i - 20) * 5);

			ready_flag = false;
			/* Set the duty cycle - keep trying until PWM is ready... */
			while (app_pwm_channel_duty_set(&PWM1, 0, 10) == NRF_ERROR_BUSY);

			/* ... or wait for callback. */
			while(!ready_flag);
			APP_ERROR_CHECK(app_pwm_channel_duty_set(&PWM1, 1, value));
			nrf_delay_ms(125);
		}
	}

}