DS1981U, UniqueWareTM iButton

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Re: DS1981U, UniqueWareTM iButton

Unread postby miod » Wed Jan 20, 2016 1:43 pm

ivelegacy wrote:it seems we can't reprogram DS1981U chips, they are read-only

Of course. That's the whole point of these chips. Some of them also have programmable memory, but there will always be some form of read-only memory used for device identification purposes.

ivelegacy wrote:I do not know the "1wire-standard"

This is basically I2C bit-banging, but over a single wire used to alternatively convey the clock and data signals. Adapting an existing I2C design to 1wire is almost straightforward, except for the device power supply (true 1wire devices have only, well, one wire, and must use some form of vampire capacity to feed off the signals it receives on the wire in order to keep state and be able to do the bit-banging correctly).
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Re: DS1981U, UniqueWareTM iButton

Unread postby robespierre » Wed Jan 20, 2016 3:49 pm

from my reading 20 years ago when they were introduced, I think I remember that every iButton has a 128-bit serial number permanently burned in. there are many variations when you go beyond that, with eeproms, smartcard-like crypto, and even full Java interpreters but I don't know if the latter are still available.
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