What Is an iButton Device?
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.
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.
The Can and Grommet
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
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
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.
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
- Real-Time Clock
- 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?
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?
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?
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.
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|© May 17, 2006, Maxim Integrated Products, Inc.
APP 3808: May 17, 2006
APPLICATION NOTE 3808,