Introduction of IoT(2): barcode & IC cards

条码技术是在计算机应用发展过程中，为消除数据录入的“瓶颈”问题而产生的，可以说是最早的自动识别技术。

1D Barcode

A barcode is an optical machine-readable representation of data.
Every barcode begins with a special start character and ends with a special stop character. ( Some may have checksum character).

不同图像的区分

UPC: 6+6

UPC: Universal Product Code is a barcode symbology, that is widely used in North America, etc, for tracking trade items in stores.
Most common form: UPC-A, 12个数字

UPC-A: 1+5+5+1

Used for marking products which are sold at retail in the USA.
**Identifies the manufacturer and specific product **.

UPC-E 1+6+1

A variation of the UPC-A symbol.
Smaller, for labeling small items.
Compression works by squeezing extra zeros out of the barcode and then automatically re-inserting them at the scanner.

Codabar: 12

Libraries, blood banks…… information processing applications.

EAN-13: 1+6+6

European Article Number, used world-wide for marking retail goods.
First 2 or 3: country code
followed 9 or 10 data digits
a single digit checksum.

一维码译码原理

激光扫描仪发出光线，光线经过条或空的反射后返回阅读器，通过光电转换器转换成电信号，进行译码。

2D Code

The advantages of 2D code over barcode

• Encode a lot of information in a small space.
• Barcode: 20 to 25 characters.
• 2D code: 100 to 2000 characters.

PDF-417

the shape of the symbol can be adjusted (to some extent) (by setting the width and allowing the height to grow with the data grow.)
看起来像是条码包裹着二维码，理论上没有长度限制

Data Matrix

四个角没有方块的二维码

QR code

Quick response code.

• Fast readability.
• Large storage capacity.
• Detected as a 2-dimensional digital image.
• The processor locates the 3 distinctive squares at the corners of the image, and normalizes image size, orientation and angle of viewing, with the aid of a smaller square near the fourth corner.
• 还可以加密；
• 污损50%仍然可以读取完整信息。

条码的应用范围：“可视”、“清晰”

可视：阅读器与条码之间没有遮挡

清晰：条码图形没有遮挡、折叠或破损

IC Card

Difference between IC Cards and magnetic cards

Traditional magnetic cards: use magnetic tape to store information.
IC Card: uses a powerful, large capacity embedded IC chip to store a large amount of information.
It can preform mathematical calculations.
It’s difficult to counterfeit and decrypt, making them a much more secure choice.

Types of IC Cards

• whether contain microprocessor: storage cards, CPU cards.
• whether need to contact with the reader: Contact smart cards, contactless smart cards.

Contact Cards

gold plated contact pads. These pads provide electrical connectivity when inserted into a reader. Cards do not contain batteries and power is supplied by the card reader.

Contactless Cards

communicate with reader through RF induction technology. and it is powered by the reader.