35 lines
1.5 KiB
ReStructuredText
35 lines
1.5 KiB
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===========
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PWM Drivers
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===========
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For the purposes of this driver, a PWM device is any device that
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generates periodic output pulses of controlled frequency and pulse
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width. Such a device might be used, for example, to perform
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pulse-width modulated output or frequency/pulse-count modulated
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output (such as might be needed to control a stepper motor).
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The NuttX PWM driver is split into two parts:
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#. An "upper half", generic driver that provides the common PWM
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interface to application level code, and
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#. A "lower half", platform-specific driver that implements the
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low-level timer controls to implement the PWM functionality.
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Files supporting PWM can be found in the following locations:
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- **Interface Definition**. The header file for the NuttX PWM
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driver reside at ``include/nuttx/timers/pwm.h``. This header
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file includes both the application level interface to the PWM
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driver as well as the interface between the "upper half" and
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"lower half" drivers. The PWM module uses a standard character
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driver framework. However, since the PWM driver is a device
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control interface and not a data transfer interface, the
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majority of the functionality available to the application is
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implemented in driver ioctl calls.
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- **"Upper Half" Driver**. The generic, "upper half" PWM driver
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resides at ``drivers/timers/pwm.c``.
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- **"Lower Half" Drivers**. Platform-specific PWM drivers reside
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in ``arch/<architecture>/src/<hardware>``
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directory for the specific processor ``<architecture>`` and for
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the specific ``<chip>`` PWM peripheral devices.
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