ibutton question

illuzion

How closely can the bs2p "mimic" an ibutton?· I have a system in place already based on 64 bit ibuttons without challenge/response or password security (DS1990A id only), which gives a 64 bit ID, and I would like to embed something a little less obvious (and removeable than a ibutton) into·the design.· So is it possible to use the owout of a bs2p to basically emulate a simple ds1990a and a reader device would read it exactly as such??· Since this design already includes an embedded version of the bs2p, it would actually eliminate the external components as well.· Are there any code examples out there for this?? I would assume the device needs to constantly poll that line to see if a reader is looking for it (using owin), and if it is then transmit its ID using owout??· or is there any advantage to doing this with a DS2480 serial to onewire converter??·
Any help appreciated
Brian
·

Bean

If your not using the ibutton then why use the 1-wire protocol ? Why can't ypu just communicate with serial ?
Bean.

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"A problem well defined, is a problem·half solved."
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illuzion

because the stick type (self contained) readers I am using are ibutton onewire.
Brian
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Jon Williams

The BASIC Stamp 2p family only support 1-Wire Master commands -- I don't think you can simulate a 1-Wire slave.

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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA

illuzion

So is this definately true?? It is not possible to simulate a onewire slave device using the BS2p's native commandset?· Next question, if not possible to·simulate a slave device using the native commandset,b·is it possible using external components (like a serial to onewire converter)?

Thanks
Brian

Jon Williams

I doubt it; 1-Wire timing is really critical. You could probably simulate a 1-Wire device using a SXmicro (not BS2sx) programmed in assembly or SX/B, but it would still be quite tricky. Keep in mind that Maxim/Dallas documentation only give details about the 1-Wire master; they have not licenced the technology to anyone nor published (to my knowledge) specific details on slave behavior -- though one could certainly infer it from the other documentation.

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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA

geekything

Not least to say that you're violating DalSemi/MAXIM's intellectual property by simulating a 1-wire device. So if you're planning on doing this with a commercial application, you might want to read up on their IP license for 1-wire technology before proceeding

Now, if you want to connect something relatively intelligent to the 1-wire bus such as a Stamp, one way to do it is with a DS2408 (not to be confused with the 2480) 1-wire 8-bit GPIO.

-marc

Ashfaq

Hello

Ineteresting thread/question. [noparse]:)[/noparse]

Well, why dont you look at the DS2401 - essentially its a DS1990A in chip form! Looks like a 3 pin transisitor, u can even get SMD packages to be more discrete if need be. that may solve you problems.

Look at:www.maxim-ic.com/quick_view2.cfm/qv_pk/2903

I have 2 more days to go as a Maxim Dallas Apps Engineer.... so thought I'd do my fair share of contribution before leaving.

Also look at my webpage (very very outof date): www.juna.co.uk

There you will see my article on a GPS tracker which uses a DS1990A.. you could use parts of the code there to read the DS1990A/DS2401.

Hope this helps.

Ashfaq