Add nuttx to the system framework, which is 10.1.0

2021-06-09 14:33:15 +08:00
parent 06c351e27c
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+===========
+PWM Drivers
+===========
+
+For the purposes of this driver, a PWM device is any device that
+generates periodic output pulses 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 NuttX PWM driver is split into two parts:
+
+#. An "upper half", generic driver that provides the common PWM
+   interface to application level code, and
+#. A "lower half", platform-specific driver that implements the
+   low-level timer controls to implement the PWM functionality.
+
+Files supporting PWM can be found in the following locations:
+
+-  **Interface Definition**. The header file for the NuttX PWM
+   driver reside at ``include/nuttx/timers/pwm.h``. This header
+   file includes both the application level interface to the PWM
+   driver as well as the interface between the "upper half" and
+   "lower half" drivers. 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 available to the application is
+   implemented in driver ioctl calls.
+-  **"Upper Half" Driver**. The generic, "upper half" PWM driver
+   resides at ``drivers/timers/pwm.c``.
+-  **"Lower Half" Drivers**. Platform-specific PWM drivers reside
+   in ``arch/``\ *<architecture>*\ ``/src/``\ *<hardware>*
+   directory for the specific processor *<architecture>* and for
+   the specific *<chip>* PWM peripheral devices.