Electronics Technology

Touch the future - with an iButton

19 May 2004 Electronics Technology

Conversant in the universal digital language of 1s and 0s, the iButton, a product of Maxim/Dallas Semiconductor, has circled the world as a peripatetic extension of the computer. iButton technology has found a home on every continent.

The button's unique form factor and features address widespread cultural and economic needs: to identify and authenticate, time- and date-stamp events, guard property, and track inventory.

So what is an iButton?

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

Its components

All iButtons use a stainless steel 'Can' for their electronic communications interface. Each 'Can' has a data contact called the 'Lid' and a ground contact which is called the 'Base'. Each of these contacts is connected to the silicon chip inside. The bottom of the device includes a flange for easily attaching the button to just about anything. The two contacts are separated by a polypropylene grommet.

By simply touching each of the two contacts one can communicate to any of the iButtons by using a '1-Wire protocol'. The 1-Wire interface has two communication speeds. Standard mode at 16 Kbps and overdrive mode at 142 Kbps.

Each iButton has a unique and unalterable address that is laser etched onto its chip inside the can. The address can be used as a key or identifier for each iButton. From these basics the iButton product line has been expanded into over 20 different products by adding different functionality to the basic button.

iButtons come in the following different varieties: ID only; Memory; Realtime Clock; Secure; and Temperature.

Information transferral

Information is transferred between an iButton and a PC with a momentary contact. The iButton is simply touched 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 the PC's serial or parallel port.

Usage, and wear

The iButton is ideal for any application where information needs to travel with a person or object. Affixed to a key fob, watch, or ring, it 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 a variety of processes to improve efficiency, such as manufacturing, delivery, and maintenance. Some versions of the iButton can be used to store cash for small transactions, such as transit systems, parking meters, and vending machines. The iButton can also be used as an electronic asset tag to store information needed to keep track of valuable capital equipment.

In terms of durability, the chip is protected by stainless steel. One can drop it, step on it, or scratch it - it is wear-tested for 10-year durability.

What is needed for a system?

There are four components fundamental to any iButton application:

* iButtons.

* A host system: this can be a PC, a laptop, or a handheld computer.

* A reader/writer device to get information into and out of the button. This can be the Blue Dot, a pen-style probe, or a handheld data collection device.

* A layer of software to interface iButtons to computers and produce the desired information in the desired format. For all iButtons, iButton-TMEX is a software platform on which to build applications. TMEX removes the tedious low-level programming of drivers and utilities. The TMEX Software and SDK are downloadable at no charge.

Advantages over other technologies

Barcodes, RFID tags, magnetic stripe, prox, and smartcards are some other technologies. Unlike bar codes and magnetic stripe cards, most of the iButtons can be read and written to. In addition, the communication rate and product breadth of iButtons goes well beyond the simple memory products typically available with RFID. As for durability, the thin plastic of smartcards is no match for the strength of the stainless-steel clad iButton. Also, when comparing these technologies on the basis of security, there is no match for the iButton.

Should a customer not wish to build an application itself, Maxim/Dallas has partners called Authorised Solutions Developers, who offer turnkey iButton systems for access control, time and attendance tracking, payroll, truck fleet maintenance, manufacturing control, fare collection, etc.

With over 85 million iButtons currently in circulation, the list of users is very long. Many of the applications are on the website at http://db.maxim-ic.com/ibutton/applications along with more detailed information about the iButton.


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