interfacing ibutton to PC using USB - Electronic Circuits Projects Diagrams Free

konzen · 9th May 2008, 12:38 PM

Hey guys,

Part of my final year project requires interfacing an ibutton to a embedded computer to serve as a user authentication feature.

My supervisor has handed me two things, namely;

a) ibutton ,model: DS1990A which is an ID only ibutton
b) ibutton reader, model: DS9092 which is has two wires coming out(1 for power and one for data(ibuttons use the 1-wire interface))

My question is, can I interface the ibutton reader to a PC using the USB interface? There are USB adapters for sale which is a basically a reader with a built in USB connector. However, I would like to construct one on my own.

Since the ibutton model only allows reading, can I just connect the data wire of the reader to the data pin of the USB jack and forget about the write pin on the USB connector. If I connect the power wire on the ibutton reader to the USB Vcc, where do I connect to USB ground to?

Has anyone done this? Thanks in advance folks

**Jay.slovak** · 9th May 2008, 02:20 PM

Hi,

Maxim produces exactly what you need, an USB interfaced 1wire/iButton reader, complete with Java source code. Check out the datasheet http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3834 . Note that you can also build this adapter from scratch, the DS2490 IC is handing everything.

Jay.

konzen · 9th May 2008, 03:53 PM

I'm aware of the USB adapter maxim is offering. however, I want to utilize the reader that I have with me right now. I have the appropriate hardware to read the ibutton but I just need advice on how to build an intermediate USB connector between the reader and the PC.

To make things clearer the reader that I have now with me is the DS9092 model as shown on this page. It has two wires coming out of it.

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2974/t/al

Can this be done? thank you.

**Jay.slovak** · 9th May 2008, 04:00 PM

That's not a reader, but only a mechanical iButton holder, which could be connected to the reader I pointed in my previous post. The 'reader' what you have only provides you access to the 1wire bus (you can't solder wires on the iButton).

konzen · 9th May 2008, 05:18 PM

Thanks. I'm gonna do more reading. Anyway have you ever developed an ibutton interface before?

blueroomelectronics · 9th May 2008, 05:30 PM

Many of us have, it's not that difficult. DalSemi has plenty of application notes.

**Jay.slovak** · 9th May 2008, 05:34 PM

Actually yes I have.

I used DS1402D-DR8 (iButton holder) and connected it via RJ-12 jack to a USB reader based on DS2490. The datasheet of DS2490 has a reference schematic that I used. It is a very simple design, but works great. The Software is free directly from Maxim.

konzen · 9th May 2008, 05:49 PM

I see.

So do you guys suggest that I obtain an adapter like you did? Or is there a way to do it with the existing probe that I have?

blueroomelectronics · 9th May 2008, 05:56 PM

You need the adapter. The probe you have contains no electronics and is meant to attach to a microcontroller or adapter.

**Jay.slovak** · 9th May 2008, 06:05 PM

You can use the probe you already have, it's the reader that you should be concerned about.

konzen · 9th May 2008, 06:07 PM

Cool. My supervisor did tell me to use a microcontroller to read the ibutton. But obtaining the microcontroller and learning how to use it requires time. So right now I'm trying to find ways of directly connecting it to the embedded computer. Guess I should get an adapter then. However, I did read somewhere on the maxim site that I could let the software handle all the reading and all I need is just a simple circuit with a pull up resistor. I might be giving that a shot.

blueroomelectronics · 9th May 2008, 06:17 PM

You can toggle an I/O pin to read an iButton. But that may not be as easy as you may think. The iButtons are very timing sensitive.

**Jay.slovak** · 9th May 2008, 06:27 PM

I suggest you first learn what an iButton is: http://www.maxim-ic.com/appnotes.cfm/an_pk/3808

konzen · 9th May 2008, 06:33 PM

I thought of doing that too but then apparently it's quite difficult lol.

Yeah I've gone through quite abit on ibuttons and I roughly know what it does. Just wanna find out alternatives methods of interfacing the ibutton.

Thanks abunch

**Jay.slovak** · 9th May 2008, 06:42 PM

I would suggest to use the Serial Port, and not USB. Embedded computers still have them. And it is much easier this way.

Have a look at http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2983 (notice the schematic diagram in the datasheet).

Jay.

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9th May 2008, 12:38 PM	(permalink)
konzen	interfacing ibutton to PC using USB Hey guys, Part of my final year project requires interfacing an ibutton to a embedded computer to serve as a user authentication feature. My supervisor has handed me two things, namely; a) ibutton ,model: DS1990A which is an ID only ibutton b) ibutton reader, model: DS9092 which is has two wires coming out(1 for power and one for data(ibuttons use the 1-wire interface)) My question is, can I interface the ibutton reader to a PC using the USB interface? There are USB adapters for sale which is a basically a reader with a built in USB connector. However, I would like to construct one on my own. Since the ibutton model only allows reading, can I just connect the data wire of the reader to the data pin of the USB jack and forget about the write pin on the USB connector. If I connect the power wire on the ibutton reader to the USB Vcc, where do I connect to USB ground to? Has anyone done this? Thanks in advance folks

9th May 2008, 02:20 PM	(permalink)
Jay.slovak	Hi, Maxim produces exactly what you need, an USB interfaced 1wire/iButton reader, complete with Java source code. Check out the datasheet http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3834 . Note that you can also build this adapter from scratch, the DS2490 IC is handing everything. Jay. __________________ "I share, thus I am" Jay.slovak Read this! ICD2 Clone Best PIC/DsPIC Bootloader Read my Inchworm ICD2 review!

9th May 2008, 03:53 PM	(permalink)
konzen	I'm aware of the USB adapter maxim is offering. however, I want to utilize the reader that I have with me right now. I have the appropriate hardware to read the ibutton but I just need advice on how to build an intermediate USB connector between the reader and the PC. To make things clearer the reader that I have now with me is the DS9092 model as shown on this page. It has two wires coming out of it. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2974/t/al Can this be done? thank you.

9th May 2008, 04:00 PM	(permalink)
Jay.slovak	That's not a reader, but only a mechanical iButton holder, which could be connected to the reader I pointed in my previous post. The 'reader' what you have only provides you access to the 1wire bus (you can't solder wires on the iButton). __________________ "I share, thus I am" Jay.slovak Read this! ICD2 Clone Best PIC/DsPIC Bootloader Read my Inchworm ICD2 review!

9th May 2008, 05:18 PM	(permalink)
konzen	Thanks. I'm gonna do more reading. Anyway have you ever developed an ibutton interface before?

9th May 2008, 05:30 PM	(permalink)
blueroomelectronics	Many of us have, it's not that difficult. DalSemi has plenty of application notes. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

9th May 2008, 05:34 PM	(permalink)
Jay.slovak	Actually yes I have. I used DS1402D-DR8 (iButton holder) and connected it via RJ-12 jack to a USB reader based on DS2490. The datasheet of DS2490 has a reference schematic that I used. It is a very simple design, but works great. The Software is free directly from Maxim. __________________ "I share, thus I am" Jay.slovak Read this! ICD2 Clone Best PIC/DsPIC Bootloader Read my Inchworm ICD2 review!

9th May 2008, 05:49 PM	(permalink)
konzen	I see. So do you guys suggest that I obtain an adapter like you did? Or is there a way to do it with the existing probe that I have?

9th May 2008, 05:56 PM	(permalink)
blueroomelectronics	You need the adapter. The probe you have contains no electronics and is meant to attach to a microcontroller or adapter. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

9th May 2008, 06:05 PM	(permalink)
Jay.slovak	You can use the probe you already have, it's the reader that you should be concerned about. __________________ "I share, thus I am" Jay.slovak Read this! ICD2 Clone Best PIC/DsPIC Bootloader Read my Inchworm ICD2 review!

9th May 2008, 06:07 PM	(permalink)
konzen	Cool. My supervisor did tell me to use a microcontroller to read the ibutton. But obtaining the microcontroller and learning how to use it requires time. So right now I'm trying to find ways of directly connecting it to the embedded computer. Guess I should get an adapter then. However, I did read somewhere on the maxim site that I could let the software handle all the reading and all I need is just a simple circuit with a pull up resistor. I might be giving that a shot.

9th May 2008, 06:17 PM	(permalink)
blueroomelectronics	You can toggle an I/O pin to read an iButton. But that may not be as easy as you may think. The iButtons are very timing sensitive. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

9th May 2008, 06:27 PM	(permalink)
Jay.slovak	I suggest you first learn what an iButton is: http://www.maxim-ic.com/appnotes.cfm/an_pk/3808 __________________ "I share, thus I am" Jay.slovak Read this! ICD2 Clone Best PIC/DsPIC Bootloader Read my Inchworm ICD2 review!

9th May 2008, 06:33 PM	(permalink)
konzen	I thought of doing that too but then apparently it's quite difficult lol. Yeah I've gone through quite abit on ibuttons and I roughly know what it does. Just wanna find out alternatives methods of interfacing the ibutton. Thanks abunch

9th May 2008, 06:42 PM	(permalink)
Jay.slovak	I would suggest to use the Serial Port, and not USB. Embedded computers still have them. And it is much easier this way. Have a look at http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2983 (notice the schematic diagram in the datasheet). Jay. __________________ "I share, thus I am" Jay.slovak Read this! ICD2 Clone Best PIC/DsPIC Bootloader Read my Inchworm ICD2 review!