a752c7ab
 elopes
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/*
* Copyright (C) 2014 Freie Universität Berlin
* Copyright (C) 2015 Eistec AB
*
* This file is subject to the terms and conditions of the GNU Lesser General
* Public License v2.1. See the file LICENSE in the top level directory for more
* details.
*/
/**
* @defgroup drivers_servo Servo Motor Driver
* @ingroup drivers_actuators
* @brief High-level driver for servo motors
* @{
*
* @file
* @brief High-level driver for easy handling of servo motors
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
* @author Joakim Nohlgård <joakim.nohlgard@eistec.se>
*/
#ifndef SERVO_H
#define SERVO_H
#include "periph/pwm.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Descriptor struct for a servo
*/
typedef struct {
pwm_t device; /**< the PWM device driving the servo */
int channel; /**< the channel the servo is connected to */
unsigned int min; /**< minimum pulse width, in us */
unsigned int max; /**< maximum pulse width, in us */
unsigned int scale_nom; /**< timing scale factor, to adjust for an inexact PWM frequency, nominator */
unsigned int scale_den; /**< timing scale factor, to adjust for an inexact PWM frequency, denominator */
} servo_t;
/**
* @brief Initialize a servo motor by assigning it a PWM device and channel
*
* Digital servos are controlled by regular pulses sent to them. The width
* of a pulse determines the position of the servo. A pulse width of 1.5ms
* puts the servo in the center position, a pulse width of about 1.0ms and
* about 2.0ms put the servo to the maximum angles. These values can however
* differ slightly from servo to servo, so the min and max values are
* parameterized in the init function.
*
* The servo is initialized with default PWM values:
* - frequency: 100Hz (10ms interval)
* - resolution: 10000 (1000 steps per ms)
*
* These default values can be changed by setting SERVO_RESOLUTION and
* SERVO_FREQUENCY macros.
* Caution: When initializing a servo, the PWM device will be reconfigured to
* new frequency/resolution values. It is however fine to use multiple servos
* with the same PWM device, just on different channels.
*
* @param[out] dev struct describing the servo
* @param[in] pwm the PWM device the servo is connected to
* @param[in] pwm_channel the PWM channel the servo is connected to
* @param[in] min minimum pulse width (in the resolution range)
* @param[in] max maximum pulse width (in the resolution range)
*
* @return 0 on success
* @return <0 on error
*/
int servo_init(servo_t *dev, pwm_t pwm, int pwm_channel, unsigned int min, unsigned int max);
/**
* @brief Set the servo motor to a specified position
*
* The position of the servo is specified in the pulse width that
* controls the servo. With default configurations, a value of 1500
* means a pulse width of 1.5 ms, which is the center position on
* most servos.
*
* In case pos is larger/smaller then the max/min values, pos will be set to
* these values.
*
* @param[in] dev the servo to set
* @param[in] pos the position to set the servo (in the resolution range)
*/
void servo_set(const servo_t *dev, unsigned int pos);
#ifdef __cplusplus
}
#endif
#endif /* SERVO_H */
/** @} */
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