motor.h

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/**
 * <rc/motor.h>
 *
 * @brief      Control 4 DC motor Channels
 *
 * The robotics cape can drive 4 DC motors bidirectionally powered only from a
 * 2-cell lithium battery pack connected to the cape. The motors will not draw
 * power from USB or the 9-18v DC Jack. Each channel can support 1.2A continuous
 * and the user must be careful to choose motors which will not exceed this
 * rating when stalled. Each channel is broken out on an independent 2-pin JST
 * ZH connector.
 *
 * @author     James Strawson
 * @date       1/31/2018
 *
 * @addtogroup Motor
 * @{
 */

#ifndef RC_MOTOR_H
#define RC_MOTOR_H

#ifdef __cplusplus
extern "C" {
#endif

#define RC_MOTOR_DEFAULT_PWM_FREQ       25000   ///< 25kHz


/**
 * @brief      Initializes all 4 motors and leaves them in a free-spin (0
 * throttle) state.
 *
 * Note, if the user is optionally using the rc_motor_standby functionality they
 * should be aware that rc_motor_init starts standby mode in a disabled state so
 * it is not necessary for the majority of users who are not interested in
 * standby mode.
 *
 * This starts the motor drivers at RC_MOTOR_DEFAULT_PWM_FREQ. To use another
 * frequency initialize with rc_motor_init_freq instead.
 *
 * @return     0 on success, -1 on failure which is usually due to lack of user
 * permissions to access the gpio and pwm systems.
 */
int rc_motor_init(void);


/**
 * @brief      Just like rc_motor_init but allows the user to set the pwm
 * frequency
 *
 * RC_MOTOR_DEFAULT_PWM_FREQ is a good frequency to start at.
 *
 * Note, if the user is optionally using the rc_motor_standby functionality they
 * should be aware that rc_motor_init starts standby mode in a disabled state so
 * it is not necessary for the majority of users who are not interested in
 * standby mode.
 *
 * @param[in]  pwm_frequency_hz  The pwm frequency in hz
 *
 * @return     0 on success, -1 on failure which is usually due to lack of user
 * permissions to access the gpio and pwm systems.
 */
int rc_motor_init_freq(int pwm_frequency_hz);


/**
 * @brief      Puts all 4 motors into a free-spin (0 throttle) state, puts the
 * h-bridges into standby mode, and closes all file pointers to GPIO and PWM
 * systems.
 *
 * @return     0 on success, -1 on failure.
 */
int rc_motor_cleanup(void);


/**
 * @brief      Toggle the H-bridges in and out of low-power standby mode.
 *
 * This is an entirely optional function as calling rc_motor_cleanup when your
 * program closes will put the h-bridges into standby mode and then calling
 * rc_motor_init at the beginning of your program will take them out of standby
 * mode. However, if the user wishes to toggle in and out of standby mode in
 * their program (for example while paused) then they can use this function.
 *
 * @param[in]  standby_en  1 to enable standby mode, 0 to disable
 *
 * @return     0 on success, -1 on failure.
 */
int rc_motor_standby(int standby_en);


/**
 * @brief      Sets the bidirectional duty cycle (power) to a single motor or
 * all motors if 0 is provided as a channel.
 *
 * @param[in]  ch    The motor channel (1-4) or 0 for all channels.
 * @param[in]  duty  Duty cycle, -1.0 for full reverse, 1.0 for full forward
 *
 * @return     0 on success, -1 on failure
 */
int rc_motor_set(int ch, double duty);


/**
 * @brief      Puts a motor into a zero-throttle state allowing it to spin
 * freely.
 *
 * This is accomplished by putting both motor terminals connected to the
 * h-bridge into a high-impedance state.
 *
 * @param[in]  ch    The motor channel (1-4) or 0 for all channels.
 *
 * @return     0 on success, -1 on failure
 */
int rc_motor_free_spin(int ch);


/**
 * @brief      Connects the motor terminal pairs together which makes the motor
 * fight against its own back EMF turning it into a brake resisting rotation.
 *
 * @param[in]  ch    The motor channel (1-4) or 0 for all channels.
 *
 * @return     0 on success, -1 on failure
 */
int rc_motor_brake(int ch);



#ifdef __cplusplus
}
#endif

#endif // RC_MOTOR_H

/** @} end group Motor */