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98 lines
3.2 KiB
C
98 lines
3.2 KiB
C
/*
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* Copyright (C) 2014 Freie Universität Berlin
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* Copyright (C) 2015 Eistec AB
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*
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* This file is subject to the terms and conditions of the GNU Lesser General
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* Public License v2.1. See the file LICENSE in the top level directory for more
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* details.
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*/
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/**
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* @defgroup driver_servo Servo Motor Driver
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* @ingroup drivers
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* @brief High-level driver for servo motors
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* @{
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*
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* @file
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* @brief High-level driver for easy handling of servo motors
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*
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* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
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* @author Joakim Gebart <joakim.gebart@eistec.se>
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*/
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#ifndef SERVO_H
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#define SERVO_H
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#include "periph/pwm.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Descriptor struct for a servo
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*/
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typedef struct {
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pwm_t device; /**< the PWM device driving the servo */
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int channel; /**< the channel the servo is connected to */
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unsigned int min; /**< minimum pulse width, in us */
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unsigned int max; /**< maximum pulse width, in us */
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unsigned int scale_nom; /**< timing scale factor, to adjust for an inexact PWM frequency, nominator */
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unsigned int scale_den; /**< timing scale factor, to adjust for an inexact PWM frequency, denominator */
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} servo_t;
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/**
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* @brief Initialize a servo motor by assigning it a PWM device and channel
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*
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* Digital servos are controlled by regular pulses sent to them. The width
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* of a pulse determines the position of the servo. A pulse width of 1.5ms
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* puts the servo in the center position, a pulse width of about 1.0ms and
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* about 2.0ms put the servo to the maximum angles. These values can however
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* differ slightly from servo to servo, so the min and max values are
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* parameterized in the init function.
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*
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* The servo is initialized with fixed PWM values:
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* - frequency: 100Hz (10ms interval)
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* - resolution: 10000 (1000 steps per ms)
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*
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* Caution: When initializing a servo, the PWM device will be reconfigured to
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* new frequency/resolution values. It is however fine to use multiple servos
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* with the same PWM device, just on different channels.
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*
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* @param[out] dev struct describing the servo
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* @param[in] pwm the PWM device the servo is connected to
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* @param[in] pwm_channel the PWM channel the servo is connected to
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* @param[in] min minimum pulse width in us
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* @param[in] max maximum pulse width in us
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*
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* @return 0 on success
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* @return <0 on error
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*/
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int servo_init(servo_t *dev, pwm_t pwm, int pwm_channel, unsigned int min, unsigned int max);
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/**
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* @brief Set the servo motor to a specified position
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*
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* The position of the servo is specified in the pulse width that controls the
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* servo. A value of 1500 means a pulse width of 1.5 ms, which is the center
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* position on most servos.
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*
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* In case pos is larger/smaller then the max/min values, pos will be set to
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* these values.
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*
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* @param[in] dev the servo to set
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* @param[in] pos the position to set the servo in us
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*
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* @return 0 on success
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* @return -1 on invalid configured channel
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* @return -2 on invalid position
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*/
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int servo_set(servo_t *dev, unsigned int pos);
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#ifdef __cplusplus
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}
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#endif
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#endif /* SERVO_H */
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/** @} */
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