Robot Control Library
pwm.h
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1 /**
2  * <rc/pwm.h>
3  *
4  * @brief C interface for the Sitara PWM driver
5  *
6  * These functions provide a general interface to all 3 PWM subsystems, each of
7  * which have two available channels A and B. PWM subsystems 1 and 2 are used
8  * for controlling the 4 motor drivers on the Robotics Cape, however they may be
9  * controlled by the user directly instead of using the motor API. PWM subsystem
10  * 0 channels A and B can be accessed on the GPS header if set up with the
11  * Pinmux API to do so. The user may have exclusive use of that subsystem.
12  *
13  *
14  * @author James Strawson
15  * @date 1/31/2018
16  *
17  * @addtogroup PWM
18  * @ingroup IO
19  * @{
20  */
21 
22 #ifndef RC_PWM_H
23 #define RC_PWM_H
24 
25 #ifdef __cplusplus
26 extern "C" {
27 #endif
28 
29 
30 /**
31  * @brief Configures subsystem 0, 1, or 2 to operate at a particular
32  * frequency.
33  *
34  * This may be called at runtime to change the pwm frequency without stopping
35  * the motors or pwm signal.
36  *
37  * @param[in] ss Subsystem 0 1 or 2
38  * @param[in] frequency The frequency in HZ
39  *
40  * @return Returns 0 on success or -1 on failure.
41  */
42 int rc_pwm_init(int ss, int frequency);
43 
44 /**
45  * @brief Stops a subsystem and puts it into a low-power state.
46  *
47  * Recommended to call before userspace program exits to ensure the PWM hardware
48  * stops.
49  *
50  * @param[in] ss subsystem 0,1,2
51  *
52  * @return Returns 0 on success or -1 on failure.
53  */
54 int rc_pwm_cleanup(int ss);
55 
56 /**
57  * @brief Sets the duty cycle of a specific pwm channel.
58  *
59  * @param[in] ss subsystem 0,1,2
60  * @param[in] ch channel 'A' or 'B'
61  * @param[in] duty between 0.0 (off) and 1.0(full on)
62  *
63  * @return Returns 0 on success or -1 on failure.
64  */
65 int rc_pwm_set_duty(int ss, char ch, double duty);
66 
67 /**
68  * @brief Like rc_pwm_set_duty() but takes a pulse width in nanoseconds.
69  *
70  * duty_ns which must range from 0 (off) to the number of nanoseconds in a
71  * single cycle as determined by the freqency specified when calling
72  * rc_pwm_init(). For example, a pwm frequency of 25kz corresponds to a maximum
73  * pulse width of 40,000ns.
74  *
75  * @param[in] ss subsystem 0,1,2
76  * @param[in] ch channel 'A' or 'B'
77  * @param[in] duty_ns The duty cycle (pulse width) in nanoseconds
78  *
79  * @return Returns 0 on success or -1 on failure.
80  */
81 int rc_pwm_set_duty_ns(int ss, char ch, unsigned int duty_ns);
82 
83 
84 #ifdef __cplusplus
85 }
86 #endif
87 
88 #endif // RC_PWM_H
89 
90 /** @} end group PWM*/
rc_pwm_init
int rc_pwm_init(int ss, int frequency)
Configures subsystem 0, 1, or 2 to operate at a particular frequency.
rc_pwm_set_duty
int rc_pwm_set_duty(int ss, char ch, double duty)
Sets the duty cycle of a specific pwm channel.
rc_pwm_set_duty_ns
int rc_pwm_set_duty_ns(int ss, char ch, unsigned int duty_ns)
Like rc_pwm_set_duty() but takes a pulse width in nanoseconds.
rc_pwm_cleanup
int rc_pwm_cleanup(int ss)
Stops a subsystem and puts it into a low-power state.