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nuttx/include/nuttx/pwm.h

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/****************************************************************************
* include/nuttx/pwm.h
*
* Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
#ifndef __INCLUDE_NUTTX_PWM_H
#define __INCLUDE_NUTTX_PWM_H
/* For the purposes of this driver, a PWM device is any device that generates
* periodic output pulses s of controlled frequency and pulse width. Such a
* device might be used, for example, to perform pulse-width modulated output or
* frequency/pulse-count modulated output (such as might be needed to control
* a stepper motor).
*
* The PWM driver is split into two parts:
*
* 1) An "upper half", generic driver that provides the comman PWM interface
* to application level code, and
* 2) A "lower half", platform-specific driver that implements the low-level
* timer controls to implement the PWM functionality.
*/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <nuttx/compiler.h>
#include <fixedmath.h>
#include <nuttx/fs/ioctl.h>
#ifdef CONFIG_PWM
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Configuration ************************************************************/
/* CONFIG_PWM - Enables because PWM driver support
* CONFIG_PWM_PULSECOUNT - Some hardware will support generation of a fixed
* number of pulses. This might be used, for example to support a stepper
* motor. If the hardware will support a fixed pulse count, then this
* configuration should be set to enable the capability.
* CONFIG_DEBUG_PWM - If enabled (with CONFIG_DEBUG and, optionally,
* CONFIG_DEBUG_VERBOSE), this will generate output that can be use dto
* debug the PWM driver.
*/
/* IOCTL Commands ***********************************************************/
/* The PWM module uses a standard character driver framework. However, since
* the PWM driver is a device control interface and not a data transfer
* interface, the majority of the functionality is implemented in driver
* ioctl calls. The PWM ioctl commands are lised below:
*
* PWMIOC_SETCHARACTERISTICS - Set the characteristics of the next pulsed
* output. This command will neither start nor stop the pulsed output.
* It will either setup the configuration that will be used when the
* output is started; or it will change the characteristics of the pulsed
* output on the fly if the timer is already started. This command will
* set the PWM characteristics and return immediately.
*
* ioctl argument: A read-only reference to struct pwm_info_s that provides
* the characteristics of the pulsed output.
*
* PWMIOC_GETCHARACTERISTICS - Get the currently selected characteristics of
* the pulsed output (independent of whether the output is start or stopped).
*
* ioctl argument: A reference to struct pwm_info_s to recevie the
* characteristics of the pulsed output.
*
* PWMIOC_START - Start the pulsed output. The PWMIOC_SETCHARACTERISTICS
* command must have previously been sent. If CONFIG_PWM_PULSECOUNT is
* defined and the pulse count was configured to a non-zero value, then
* this ioctl call will, by default, block until the programmed pulse count
* completes. That default blocking behavior can be overridden by using
* the O_NONBLOCK flag when the PWM driver is opened.
*
* ioctl argument: None
*
* PWMIOC_STOP - Stop the pulsed output. This command will stop the PWM
* and return immediately.
*
* ioctl argument: None
*/
#define PWMIOC_SETCHARACTERISTICS _PWMIOC(1)
#define PWMIOC_GETCHARACTERISTICS _PWMIOC(2)
#define PWMIOC_START _PWMIOC(3)
#define PWMIOC_STOP _PWMIOC(4)
/****************************************************************************
* Public Types
****************************************************************************/
/* This structure describes the characteristics of the pulsed output */
struct pwm_info_s
{
uint32_t frequency; /* Frequency of the pulse train */
ub16_t duty; /* Duty of the pulse train, "1"-to-"0" duration.
* Maximum: 65535/65536 (0x0000ffff)
* Minimum: 1/65536 (0x00000001) */
#ifdef CONFIG_PWM_PULSECOUNT
uint32_t count; /* The number of pulse to generate. 0 means to
* generate an indefinite number of pulses */
#endif
};
/* This structure is a set a callback functions used to call from the upper-
* half, generic PWM driver into lower-half, platform-specific logic that
* supports the low-level timer outputs.
*/
struct pwm_lowerhalf_s;
struct pwm_ops_s
{
/* This method is called when the driver is opened. The lower half driver
* should configure and initialize the device so that it is ready for use.
* It should not, however, output pulses until the start method is called.
*/
CODE int (*setup)(FAR struct pwm_lowerhalf_s *dev);
/* This method is called when the driver is closed. The lower half driver
* should stop pulsed output, free any resources, disable the timer hardware, and
* put the system into the lowest possible power usage state
*/
CODE int (*shutdown)(FAR struct pwm_lowerhalf_s *dev);
/* (Re-)initialize the timer resources and start the pulsed output. The
* start method should return an error if it cannot start the timer with
* the given parameter (frequency, duty, or optionally pulse count)
*/
#ifdef CONFIG_PWM_PULSECOUNT
CODE int (*start)(FAR struct pwm_lowerhalf_s *dev,
FAR const struct pwm_info_s *info,
FAR void *handle);
#else
CODE int (*start)(FAR struct pwm_lowerhalf_s *dev,
FAR const struct pwm_info_s *info);
#endif
/* Stop the pulsed output and reset the timer resources*/
CODE int (*stop)(FAR struct pwm_lowerhalf_s *dev);
/* Lower-half logic may support platform-specific ioctl commands */
CODE int (*ioctl)(FAR struct pwm_lowerhalf_s *dev,
int cmd, unsigned long arg);
};
/* This structure is the generic form of state structure used by lower half
* timer driver. This state structure is passed to the pwm driver when the
* driver is initialized. Then, on subsequent callbacks into the lower half
* timer logic, this structure is provided so that the timer logic can
* maintain state information.
*
* Normally that timer logic will have its own, custom state structure
* that is simply cast to struct pwm_lowerhalf_s. In order to perform such casts,
* the initial fields of the custom state structure match the initial fields
* of the following generic PWM state structure.
*/
struct pwm_lowerhalf_s
{
/* The first field of this state structure must be a pointer to the PWM
* callback structure:
*/
FAR const struct pwm_ops_s *ops;
/* The custom timer state structure may include additional fields after
* the pointer to the PWM callback structure.
*/
};
/****************************************************************************
* Public Data
****************************************************************************/
/****************************************************************************
* Public Function Prototypes
****************************************************************************/
#ifdef __cplusplus
#define EXTERN extern "C"
extern "C" {
#else
#define EXTERN extern
#endif
/****************************************************************************
* "Upper-Half" PWM Driver Interfaces
****************************************************************************/
/****************************************************************************
* Name: pwm_register
*
* Description:
* This function binds an instance of a "lower half" timer driver with the
* "upper half" PWM device and registers that device so that can be used
* by application code.
*
* When this function is called, the "lower half" driver should be in the
* reset state (as if the shutdown() method had already been called).
*
* Input parameters:
* path - The full path to the driver to be registers in the NuttX pseudo-
* filesystem. The recommended convention is to name all PWM drivers
* as "/dev/pwm0", "/dev/pwm1", etc. where the driver path differs only
* in the "minor" number at the end of the device name.
* dev - A pointer to an instance of lower half timer driver. This instance
* is bound to the PWM driver and must persists as long as the driver
* persists.
*
* Returned Value:
* Zero on success; a negated errno value on failure.
*
****************************************************************************/
EXTERN int pwm_register(FAR const char *path, FAR struct pwm_lowerhalf_s *dev);
/****************************************************************************
* Name: pwm_expired
*
* Description:
* If CONFIG_PWM_PULSECOUNT is defined and the pulse count was configured
* to a non-zero value, then the "upper half" driver will wait for the
* pulse count to expire. The sequence of expected events is as follows:
*
* 1. The upper half driver calls the start method, providing the lower
* half driver with the pulse train characteristics. If a fixed
* number of pulses is required, the 'count' value will be nonzero.
* 2. The lower half driver's start() methoc must verify that it can
* support the request pulse train (frequency, duty, AND pulse count).
* It it cannot, it should return an error. If the pulse count is
* non-zero, it should set up the hardware for that number of pulses
* and return success. NOTE: That is CONFIG_PWM_PULSECOUNT is
* defined, the start() method receives an additional parameter
* that must be used in this callback.
* 3. When the start() method returns success, the upper half driver
* will "sleep" until the pwm_expired method is called.
* 4. When the lower half detects that the pulse count has expired
* (probably through an interrupt), it must call the pwm_expired
* interface using the handle that was previously passed to the
* start() method
*
* Input parameters:
* handle - This is the handle that was provided to the lower-half
* start() method.
*
* Returned Value:
* None
*
* Assumptions:
* This function may be called from an interrupt handler.
*
****************************************************************************/
#ifdef CONFIG_PWM_PULSECOUNT
EXTERN void pwm_expired(FAR void *handle);
#endif
/****************************************************************************
* Platform-Independent "Lower-Half" PWM Driver Interfaces
****************************************************************************/
#undef EXTERN
#ifdef __cplusplus
}
#endif
#endif /* CONFIG_PWM */
#endif /* __INCLUDE_NUTTX_PWM_H */
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