25.4 Basics of Electronic Circuit

Here, we will explain the basic knowledge of electronic circuit.

25.4.1 Short and Resistance

Short is also generally referred to as a short circuit, which means that two wires with different potentials are directly connected to each other, such as connecting a (+) wire and a (-) wire without a resistor in a circuit where electricity is supplied. When this direct connection is made, excessive current flows for a moment and spark occurs.

25.3 Basics of Electricity/Electronics

Here, we will explain the basics of electricity and electronics.

If you need additional information, please refer to the following:

■ http://portal.hrd.go.kr/EL/contents/084/01/ch01_02.htm

■ http://cafe.daum.net/kneeng

■ http://blog.daum.net/hongbkim/2542

■ http://blog.naver.com/dhjdhj11/150184044066

25.2.3 Precautions and Features in Using GPIO

● Precautions in using GPIO pin

■ When powering Raspberry Pi, make sure that metal object does not touch the GPIO pin.

■ Do not supply more than total 250mA current from 5V power pin.

■ Do not supply more than total 50mA current from 3.3V power pin.

■ Do not supply higher than 3.3V to all GPIO pins at the input.

■ Do not use more than 3mA current per pin at the output.

■ Do not supply higher than 5V power to Raspberry Pi.

25.2.2 GPIO Port Details

25.2.2.1 GPIO Basics

There are various kinds of GPIO interface pins in Raspberry Pi. Each pin has its own purpose, and several pins are used together to make a specific circuit.

● DNC (Do Not Connect )

25.2 GPIO Details

25.2.1 GPIO Device

25.2.1.1 GPIO Pin Layout

Since Raspberry Pi B+ model, Raspberry Pi board has a 40-pin GPIO connector with 2 male headers arranged on the left side of SD card slot. The spacing between each header is 2.54 mm (0.1 inches), which is one of the standard spacings used in electronics and is the standard spacing for prototyping platforms including stripeboard and breadboard.

25.1 Raspberry Pi and External Interface

25.1.1 Meaning of External Interface

Standard PCs like regular desktops can run the same program much faster than Raspberry Pi. However, Raspberry Pi has a capability that these standard PCs can not provide, which is a bidirectional interface with external devices. Raspberry Pi can communicate with and control devices outside the system through an interface with external devices. It can receive input or output through an external device, or control the external device. It is possible to receive a various measuring values ​​from an external sensor, to determine the situation, and to perform appropriate processing accordingly, or to build a system for directly controlling an external system by creating an embedded program.

Chapter 25 External Interface

Chapter’s Main Topics

Raspberry Pi can communicate with and control devices outside the system through an interface with external devices. The core device of the Raspberry Pi used here is GPIO (General Purpose Input Output) port. Here, we discuss how to interface with external devices using GPIO.

It includes descriptions on the following topics:
■ GPIO Details

■ Fundamentals of electricity/electronics

■ Fundamentals of Electronic circuit

■ Preparing interface

■ GPIO Library

■ Digital Input/Output interface

■ Interface using sensor