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iButton FAQ

iButtons
 
 
What is an iButton?
How does an iButton communicate?
What are iButtons being used for?
How long does an iButton last? How durable is it?
What are the basic components I need to work with iButtons?
What's the most popular iButton accessory?
How do I mount an iButton to a stationary object?
How can I use iButtons for Web site access?
How can I use iButtons for software copyright protection?
Which iButtons will TMEX work with?
Where can I contact an iButton developer?
What is the ROM ID number?
Does Maxim offer devices that have customized 64bit ROM values?
If a custom ROM part is developed for one customer, can others purchase it?
Some of the iButtons have two package types listed, F3 and F5. What is the difference?
Can more than one iButton co-exist on the 1-Wire line?
What protection is needed for the iButtons against ESD?
In the data sheet for Temperature/Humidity Sensor DS1923 it states that the user should occassionally test the accuracy of the readings. Do you have a recommend calibration schedule for this device (once per year, once per month, etc.)?
Is there a fob for the F3 can?
Are the iButtons RoHS compliant?
What is the iButton made of?
Can the markings on the iButton be changed? Can the iButton come with a different company logo on it?
 
 
Q1:
What is an iButton?
 
See the Application Note below with the same title.
 
http://www.maximintegrated.com/appnotes.cfm/an_pk/3808
 
Q2:
How does an iButton communicate?
 
The iButton is a slave device and requires a master to initiate communication to it. A master can be a PC or a micro processor. With the master constantly polling the iButtons, communication to iButtons can be started by a simple touch to a 1-Wire interface called a Blue Dot Receptor. Every iButton has a unique 64-bit serial number, which gives it a unique 1-Wire network address.
 
Q3:
What are iButtons being used for?
 
The iButton is ideal for any application where information needs to travel with a person or object. This includes point-of-sale transactions, remote access authorization, data logging (including time/temperature/humidity), maintenance and quality control. Because every iButton communicates a unique serial number, iButtons are always addressable and able to be located on a network.

Information is transferred between the iButton and host with a momentary contact.

Click here to see iButton Applications from around the world.
 
Q4:
How long does an iButton last? How durable is it?
 
Thanks to sealed stainless steel, you can drop it, step on it, or scratch it. The iButton is wear-tested for 10-year durability and a million hot contacts.
 
Q5:
What are the basic components I need to work with iButtons?
 
You need four things to work with iButtons:
1. iButtons.
2. A host system -- a PC, a laptop, or a hand-held computer.
3. A 1-Wire Adapter and iButton Probe to get information into and out of the button.
4. Software (links below)
 
1-Wire for Windows (TMEX)
1-Wire Public Domain Kit
1-Wire API for Java
 
Q6:
What's the most popular iButton accessory?
 
Nearly 2 million public transit passengers in Istanbul carry their iButton on a plastic key fob. It's the simplest way to mount an iButton for applications that require only momentary contact. After snapping in the iButton, the fob can be attached to a key ring. Fob types vary to fit the depth of the iButton they will carry and offer the choice of angled or straight shapes.
 
iButton Fobs
 
Q7:
How do I mount an iButton to a stationary object?
 
Check out the Mounting Options in our Product Section to find what you need. You will find a versatile assortment of mounts, lock rings, flanges and adhesive pads. Also, our partners have designed several different options for your consideration.
 
iButton Mounting Options
Partner Mounting Products
 
Q8:
How can I use iButtons for Web site access?
 
We have created the 1-Wire API for Java. With this, a programmer can write a simple Java applet. Keep in mind that it must be digitally signed. Contact the Automatic Information BU and request the source to an example signed applet.
 
http://support.maximintegrated.com/ibutton
 
Q9:
How can I use iButtons for software copyright protection?
 
When a copy of a software application is purchased, the company that developed the software sends an iButton (and a DS9490B USB iButton holder) with the software. For the end-user to invoke the application, an iButton must be present and supply the program with valid information in order for it to operate. This way, many copies of the program can be made, but only those invoked with valid iButtons will function. For more information, see the link below.
 
1-Wire Software Authorization Kit
 
Q10:
Which iButtons will TMEX work with?
 
All of them! All iButtons have a unique serial number that TMEX can search for and find. Also, the current memory-based iButtons are supported with a file system in TMEX. Since TMEX includes all of the basic 1-Wire communication functions, it is compatible with all current and future iButton products.
 
1-Wire Drivers for Windows (TMEX)
 
Q11:
Where can I contact an iButton developer?
 
iButton developers are found all over the world. See the Solutions Search to search by developer product, name or location.
 
Search by Product Needs
Search by Developer Name
Search by Location
 
Q12:
What is the ROM ID number?
 
The ROM ID number is a unique ROM code that is 64 bits long. This number is factory lasered into each 1-Wire device. This assures absolute traceability because no two parts have the same number. The first 8 bits are a 1-Wire family code. The next 48 bits are a unique serial number. The last 8 bits are the CRC of the first 56 bits.
 
Q13:
Does Maxim offer devices that have customized 64bit ROM values?
 
Yes, however there are some delivery restrictions, NRE costs, and minimum quantities to purchase that vary depending on the part, so please contact Maxim at the URL below for complete details.
 
http://support.maximintegrated.com/1-wire
 
Q14:
If a custom ROM part is developed for one customer, can others purchase it?
 
No, only the customer that has set up the Custom ROM part has the right to buy it. This can act as a protective device to prevent reverse engineering or copying of a product.
 
Q15:
Some of the iButtons have two package types listed, F3 and F5. What is the difference?
 
The only difference between the F3 and F5 is the height of the can. The F3 is 3.10mm and the F5 is 5.89mm.
If humans are going to be interfacing with the iButton (picking it up), the F5 can is easier to handle.
 
Q16:
Can more than one iButton co-exist on the 1-Wire line?
 
Yes, due to the unique ROM ID number in each iButton, a number of iButtons can be on the same 1-Wire line and each can be addressed individually.
 
Q17:
What protection is needed for the iButtons against ESD?
 
The iButtons are very resistance to ESD. Some are rated up to 27KV. Most are good to at least 8KV. So little, if any, extra protection is needed for the iButtons.
 
Q18:
In the data sheet for Temperature/Humidity Sensor DS1923 it states that the user should occassionally test the accuracy of the readings. Do you have a recommend calibration schedule for this device (once per year, once per month, etc.)?
 
The recalibration statement is a disclaimer. The sensor is exposed and it is possible for customers to use the DS1923 in a contaminated, dirty, polluted, etc environment. If that happened, the sensor would drift away from calibration due to contamination. Depending upon the environment, it might need recalibration after a short period. Since we have no control over this, we want to alert people that the accuracy could change.
 
Q19:
Is there a fob for the F3 can?
 
Maxim does not make a fob for the F3 can, but there is a list of companies that do make fobs. Some of them will work with the F3 fob and some of the fobs can be customized with company information
 
Fobs company list
 
Q20:
Are the iButtons RoHS compliant?
 
Maxim is in the process of making all the iButtons RoHS compliant. In an effort to keep our customers informed as to the status of this conversion, there is a website that allows customers to lookup their iButton part number to see if the RoHS part is available.
 
Lookup Lead-Free/RoHS Products and Content Data
 
Q21:
What is the iButton made of?
 
The iButton metal "can" is Type 305 Stainless Steel and the insulating grommet is molded from a polypropylene homopolymer resin that has a carbon black additive to inhibit breakdown due to ultraviolet light.
 
Q22:
Can the markings on the iButton be changed? Can the iButton come with a different company logo on it?
 
Yes, it is possible to get the iButton with custom branding. Contact the Applications Department at the URL below.
 
http://support.maximintegrated.com/ibutton