README
^^^^^^

This directory contains various device drivers -- both block and
character drivers as well as other more specialized drivers.

Contents:
- Files in this directory
- Subdirectories of this directory
- Skeleton files

Files in this directory
^^^^^^^^^^^^^^^^^^^^^^^

dev_null.c and dev_zero.c
These files provide the standard /dev/null and /dev/zero devices. See
include/nuttx/drivers/drivers.h for prototypes of functions that should
be called if you want to register these devices (devnull_register()
and devzero_register()).

ramdisk.c
Can be used to set up a block of memory or (read-only) FLASH as
a block driver that can be mounted as a file system. See
include/nuttx/drivers/ramdisk.h.

rwbuffer.c
A facility that can be used by any block driver in-order to add
writing buffering and read-ahead buffering.

Subdirectories of this directory:
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

analog/
This directory holds implementations of analog device drivers.
This includes drivers for Analog to Digital Conversion (ADC) as
well as drivers for Digital to Analog Conversion (DAC).
See include/nuttx/analog/*.h for registration information.

audio/
Audio device drivers. See include/nuttx/audio/audio.h for interface
definitions. See also the audio subsystem at nuttx/audio/.

bch/
Contains logic that may be used to convert a block driver into
a character driver. This is the complementary conversion as that
performed by loop.c. See include/nuttx/fs/fs.h for registration
information.

can/
This is the CAN drivers and logic support. See include/nuttx/can/can.h
for usage information.

contactless/
Contactless devices are related to wireless devices. They are not
communication devices with other similar peers, but couplers/interfaces
to contactless cards and tags.

crypto/
Contains crypto drivers and support logic, including the /dev/urandom
device.

eeprom/
An EEPROM is a form of Memory Technology Device (see drivers/mtd).
EEPROMs are non-volatile memory like FLASH, but differ in underlying
memory technology and differ in usage in many respects: They may not
be organized into blocks (at least from the standpoint of the user)
and it is not necessary to erase the EEPROM memory before re-writing
it. In addition, EEPROMs tend to be much smaller than FLASH parts,
usually only a few kilobytes vs megabytes for FLASH. EEPROM tends to
be used to retain a small amount of device configuration information;
FLASH tends to be used for program or massive data storage. For these
reasons, it may not be convenient to use the more complex MTD
interface but instead use the simple character interface provided by
the EEPROM drivers.

i2c/
I2C drivers and support logic. See include/nuttx/i2c/i2c_master.h

i2s/
I2S drivers and support logic. See include/nuttx/audio/i2s.h

input/
This directory holds implementations of human input device (HID)
drivers. This includes such things as mouse, touchscreen, joystick,
keyboard and keypad drivers. See include/nuttx/input/*.h for
registration information.

Note that USB HID devices are treated differently. These can be
found under usbdev/ or usbhost/.

lcd/
Drivers for parallel and serial LCD and OLED type devices. These
drivers support interfaces as defined in include/nuttx/lcd/lcd.h

leds/
Various LED-related drivers including discrete as well as PWM-
driven LEDs.

loop/
Supports the standard loop device that can be used to export a
file (or character device) as a block device. See losetup() and
loteardown() in include/nuttx/fs/fs.h.

mmcsd/
Support for MMC/SD block drivers. MMC/SD block drivers based on
SPI and SDIO/MCI interfaces are supported. See include/nuttx/mmcsd.h
and include/nuttx/sdio.h for further information.

mtd/
Memory Technology Device (MTD) drivers. Some simple drivers for
memory technologies like FLASH, EEPROM, NVRAM, etc. See
include/nuttx/mtd/mtd.h

(Note: This is a simple memory interface and should not be
confused with the "real" MTD developed at infradead.org. This
logic is unrelated; I just used the name MTD because I am not
aware of any other common way to refer to this class of devices).

net/
Network interface drivers. See also include/nuttx/net/net.h

pipes/
FIFO and named pipe drivers. Standard interfaces are declared
in include/unistd.h

power/
Power management (PM) driver interfaces. These interfaces are used
to manage power usage of a platform by monitoring driver activity
and by placing drivers into reduce power usage modes when the
drivers are not active.

pwm/
Provides the "upper half" of a pulse width modulation (PWM) driver.
The "lower half" of the PWM driver is provided by device-specific
logic. See include/nuttx/timers/pwm.h for usage information.

sensors/
Drivers for various sensors. A sensor driver differs little from
other types of drivers other than they are use to provide measurements
of things in environment like temperature, orientation, acceleration,
altitude, direction, position, etc.

DACs might fit this definition of a sensor driver as well since they
measure and convert voltage levels. DACs, however, are retained in
the analog/ sub-directory.

serial/
Front-end character drivers for chip-specific UARTs. This provide
some TTY-like functionality and are commonly used (but not required for)
the NuttX system console. See also include/nuttx/serial/serial.h

spi/
SPI drivers and support logic. See include/nuttx/spi/spi.h

syslog/
System logging devices. See include/syslog.h and include/nuttx/syslog/syslog.h

timers/
Includes support for various timer devices including:

- An "upper half" for a generic timer driver. See
include/nuttx/timers/timer.h for more information.

- An "upper half" for a generic watchdog driver. See
include/nuttx/timers/watchdog.h for more information.

- RTC drivers

usbdev/
USB device drivers. See also include/nuttx/usb/usbdev.h

usbhost/
USB host drivers. See also include/nuttx/usb/usbhost.h

video/
Video-related drivers. See include/nuttx/video/.

wireless/
Drivers for various wireless devices.

Skeleton Files
^^^^^^^^^^^^^^

Skeleton files are "empty" frameworks for NuttX drivers. They are provided to
give you a good starting point if you want to create a new NuttX driver.
The following skeleton files are available:

drivers/lcd/skeleton.c -- Skeleton LCD driver
drivers/mtd/skeleton.c -- Skeleton memory technology device drivers
drivers/net/skeleton.c -- Skeleton network/Ethernet drivers
drivers/usbhost/usbhost_skeleton.c -- Skeleton USB host class driver