14.1.4 Network Device
14.1.4.1 Characteristics of Network Device
In Linux, a network device is thought of as an entity that sends and receives data packets. A network device is usually a physical device, such as an Ethernet card. However, there are some network devices defined with only software, such as loopback device that is used to send data to itself.
14.1.3 Block Device
14.1.3.1 Block Device Characteristics
The block device inputs and outputs data in unit of block when processing data in the device, and increases the processing performance by placing a intermediate buffer.
14.1.2 Character Device
14.1.2.1 Charateristics
The character device is the simplest of all Linux devices, and it inputs and outputs data in character unit when processing data in the device, and there is no intermediate buffer.
14.1 Device Overview
14.1.1 Device Type and “/dev” Directory
In the devices used in Linux, there are character device such as keyboards, block device such as disk, and network device such as Ethernet.
Chapter 14 Understanding Device
Chapter’s Main Topics
This charpter describes the various device available on Linux systems and the “/dev” file that contains information about these devices, and describes the characteristics of USB device.
It includes descriptions on the following topics:
■ Device type and “/dev” directory
■ Character device
■ Block device
■ Network device
■ Usb device
3.9 Camera
With Raspberry Pi, you can also use the camera to record various types of pictures or record movies. There are many kinds of cameras that can be connected to Raspberry Pi, and there are two types of camera that supports USB camera and supports CSI port of Raspberry Pi on a large scale.
3.9.1 USB Camera
The USB camera is easily available on the market. It is connected to the USB port and does not need any special installation work.
3.8.2 TFT-LCD
Raspberry Pi supports DSI (Digital Serial Interface) connection to support TFT-LCD display. You may purchase and use parts that support DSI port among the items sold on the market, and then it is not easy to obtain such a TFT-LCD in reality.
Below is the 7 “Touchscreen Monitor LCD with 800 x 480 display, officially sold by the Raspberry Pi Foundation. This allows you to display all information on the LCD like a tablet. This LCD connects to its own adapter board, and the adapter board is connected to the DSI port on the main board of Raspberry Pi by a ribbon cable, and is supplied with power through the GPIO port. The latest Raspbian operating system already integrates touchscreen driver that supports a 10-finger touch and on-screen keyboard, so you can operate the system without using a mouse or keyboard.
3.8 Video Output
3.8.1 HDMI Cable and HDMI Supporting Monitor
Raspberry Pi supports HDMI (High Definition Multimedia Interface) output as basic video output, and supports HDMI video port on board.
If you want to connect Raspberry Pi to an external display device using HDMI video port, you need HDMI Type-A cable. A video image of Raspberry Pi will be output through this cable.
3.7.2 Mouse
Raspberry Pi works well without a mouse connection. You may not need a mouse when using Raspberry Pi for a special purpose. You may also not need a mouse to connect to Raspberry Pi only via the network. However, it may be convenient to use a mouse when you need to purchase Raspberry Pi and install the operating system or install applications.
3.7 Input Device
3.7.1 Keyboard
Raspberry Pi works fine even if keyboard is not connected. Keyboard may not be necessary when you connect and use Raspberry Pi to a machine or facility or for other special purposes. Also, when connecting to Raspberry Pi only via network, you may not need a keyboard either. But when you need to purchase Raspberry Pi and install an operating system or install an application at first, you have to connect a keyboard.