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