What Is an iButton?
This application note is a broad introduction to the iButton. It discusses the iButton basics: what it is, how it is
constructed, and some of its applications. It explains how a system can communicate to the iButton through its
1-Wire interface. The note also describes: types of iButtons; iButton durability; its guaranteed unique 64-bit
serial number; and available iButton accessories.
Introduction
The iButton® 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 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
An iButton 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 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, Reading and
Writing iButtons via Serial Interfaces.
The Address
Each iButton 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.
2700000095C33108
iButton Versions
The iButton product line now comprises over 20 different products with different functionality added to the basic
button. iButtons come in the following varieties:
Click one of the iButton types below to view all products in that category.
l Address Only
l Memory
l Real-Time Clock
l Secure
l Data Loggers
How Do I Get Information Into and Out of the iButton?
Information is transferred between your iButton and a PC with a momentary
contact at up to 142kbps. You simply touch your iButton 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/Dallas Direct for pricing and availability.
The iButton is also the ultimate information carrier for AutoID and many portable applications. All the latest
handheld computers and PDAs can communicate with iButtons. For a full listing of all portable devices that
communicate with iButtons, go to the iButton Solutions Search.
More Infor
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