APPLICATION NOTE 3808

What Is an iButton Device?

By:  Brian Hindman, Senior Member Technical Staff, Software

Abstract: This application note is a broad introduction to the iButton® device. It discusses the iButton device basics: what it is, how it is constructed, and some of its applications. It explains how a system can communicate to the iButton device through its 1-Wire® interface. The note also describes: types of iButton devices; iButton device durability; its guaranteed unique 64-bit serial number; and available iButton accessories.

Introduction

iButton Can The iButton® device is a computer chip enclosed in a 16mm thick stainless steel can. Because of this unique and durable container, up-to-date information can travel with a person or object anywhere they go. The steel iButton device can be mounted virtually anywhere because it is rugged enough to withstand harsh environments, indoors or outdoors. It is small and portable enough to attach to a key fob, ring, watch, or other personal items, and be used daily for applications such as access control to buildings and computers, asset management, and various data logging tasks.

iButton Components

The Can and Grommet

iButton Can An iButton device uses its stainless steel 'can' as an electronic communications interface. Each can has a data contact, called the 'lid', and a ground contact, called the 'base'. Each of these contacts is connected to the silicon chip inside. The lid is the top of the can; the base forms the sides and the bottom of the can and includes a flange to simplify attaching the button to just about anything. The two contacts are separated by a polypropylene grommet.

The 1-Wire Interface

1-Wire Interface By simply touching the iButton device to the two contacts described above, you can communicate with it through our 1-Wire® protocol. The 1-Wire interface has two communication speeds: standard mode at 16kbps, and overdrive mode at 142kbps. For more information, please see our application note 3989, "Add Control, Memory, Security, and Mixed-Signal Functions with a Single Contact."

The Address

Each iButton device has a unique and unalterable address laser etched onto its chip inside the can. The address (e.g. 2700000095C33108) can be used as a key or identifier for each iButton device.

iButton Versions

The iButton product line now comprises over 20 different products with different functionality added to the basic button. iButton devices come in the following varieties:
  • Address Only
  • Memory
  • Real-Time Clock
  • Secure
  • Data Loggers
See tutorial 1796, "Overview of 1-Wire Technology and Its Use," for more details about the products.

How Do I Get Information Into and Out of the iButton Device?

Blue Dot Receptor Information is transferred between your iButton device and a PC with a momentary contact at up to 142kbps. You simply touch your iButton device to a Blue Dot receptor or other iButton probe, which is connected to a PC. The Blue Dot receptor is cabled to a 1-Wire adapter that is attached to a spare PC port. 1-Wire adapters exist for USB, serial, and parallel ports. The Blue Dot receptor and 1-Wire adapter are inexpensive. See our Maxim Direct for pricing and availability.
The iButton device is also the ultimate information carrier for AutoID and many portable applications. All the latest handheld computers and PDAs can communicate with iButton devices. For a full listing of all portable devices that communicate with iButton devices, go to the iButton Solutions Search.

How Durable Is an iButton Device?

Mud Photo The silicon chip within the iButton device is protected by the ultimate durable material: stainless steel. You can drop an iButton device, step on it, or scratch it. The iButton device is wear-tested for 10-year durability.

What Can I Do with the iButton Device?

Door Lock The iButton device is ideal for any application where information needs to travel with a person or object. Affixed to a key fob, watch, or ring, an iButton device can grant its owner access to a building, a PC, a piece of equipment, or a vehicle. Attached to a work tote, it can measure processes to improve efficiency, such as manufacturing, delivery, and maintenance. Some iButton devices can be used to store electronic cash for small transactions, such as transit systems, parking meters, and vending machines. The iButton device can also be used as an electronic asset tag to store information needed to keep track of valuable capital equipment. Click here to see some of the iButton Applications used around the world.

What Do I Need to Put Together an iButton Application?

There are four components fundamental to any iButton application:
  • An iButton device
  • A host system: this can be a PC, a laptop, a handheld computer, or an embedded system.
  • A reader/writer device to get information into and out of the button. This can be the Blue Dot mentioned above, a pen-style probe, or a handheld device.
  • A layer of software to interface iButton devices to computers and produce the desired information in the desired format. Several software development kits (SDKs) are downloadable from this site at no charge. For a list of SDKs and links to download, see this page. We also offer 1-Wire Drivers for Microsoft platforms, along with the OneWireViewer, a demo application that can read/write/exercise any iButton device.

How Much Does It Cost to Build a Simple iButton Application?

Under $50 (US$), plus your programming time.
  • iButton devices cost between $2 to $95 in quantities of one; larger quantities are discounted.
  • The Blue Dot receptor and 1-Wire Adapter, which together make a simple reader/writer device, cost between $38 and $43.
  • The OneWireViewer demo software and SDKs are free from our web site.
That is all you need to get started. You can review our Product Section and Online Store to get all product details and exact costs for all components, along with quantity discounts.

What Are the Advantages of iButton Devices over Other Technologies?

When developing an iButton solution for an application, you can consider many complementary technologies. Bar codes, RFID tags, magnetic stripe, prox, and smart cards are some of the possibilities. Unlike bar codes and magnetic stripe cards, most of the iButton devices can be read AND be written to. In addition, the communication rate and product breadth of iButton devices go well beyond the simple memory products typically available with RFID. As for durability, the thin plastic of smart cards is no match for the strength of the stainless-steel-clad iButton device.

I Do Not Want to Build My Application Myself. Do You Provide Turnkey Solutions?

We have partnered with a number of companies called Authorized Solutions Developers, ASDs for short, who develop turnkey iButton systems for access control, time and attendance tracking, payroll, truck fleet maintenance, manufacturing control, fare collection, and more. The ASDs can also develop custom iButton applications for you—just talk to them. You can use our iButton Solutions Search to find our partners' solutions available worldwide.

Who Is Using the iButton Device?

With over 175 million iButton devices currently in circulation, the list of users is very long. You can read about many of the applications here.
Also, take a look at our iButton videos for more information on how people are using the iButton device.


1-Wire is a registered trademark of Maxim Integrated Products, Inc.

iButton is a registered trademark of Maxim Integrated Products, Inc.



Related Parts
DS1402D-DR8 1-Wire Network Cables  
DS1904 iButton RTC  
DS1920 Temperature iButton  
DS1921G Thermochron iButton Device  
DS1921H High-Resolution Thermochron iButton Devices  
DS1921Z High-Resolution Thermochron iButton Devices  
DS1922E iButton High-Temperature Logger with 8KB Data-Log Memory  
DS1922L iButton Temperature Loggers with 8KB Data-Log Memory  
DS1922T iButton Temperature Loggers with 8KB Data-Log Memory  
DS1923 iButton Hygrochron Temperature/Humidity Logger with 8KB Data-Log Memory  
DS1961S iButton 1Kb EEPROM with SHA-1 Engine  
DS1963S iButton Monetary Device with SHA-1 Function  
DS1971 iButton 256-Bit EEPROM  
DS1972 iButton 1024-Bit EEPROM  
DS1973 iButton 4Kb EEPROM Free Samples  
DS1977 iButton 32KB EEPROM  
DS1982 iButton 1Kb Add-Only Free Samples  
DS1985 iButton 16Kb Add-Only Free Samples  
DS1990A iButton Serial Number Free Samples  
DS1990R Serial Number iButton  
DS1992 iButton 1Kb/4Kb Memory Free Samples  
DS1993 iButton 1Kb/4Kb Memory Free Samples  
DS1995 iButton 16Kb Memory Free Samples  
DS1996 iButton 64Kb Memory Free Samples  
DS9097U-S09 Universal 1-Wire COM Port Adapter  


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© May 17, 2006, Maxim Integrated Products, Inc.
The content on this webpage is protected by copyright laws of the United States and of foreign countries. For requests to copy this content, contact us.

APP 3808: May 17, 2006
APPLICATION NOTE 3808, AN3808, AN 3808, APP3808, Appnote3808, Appnote 3808