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The Dallas 1-wire protocol saga -- AN126

This is exactly what I plan to do, so it would seem that a study of this 12 page note would be worthwhile. What follows are my notes.

There is a dedicated chip (DS2480B) to provide a master for the 1-wire bus, and it is still available from Digikey for $11 each. A bit pricey and almost certainly unnecessary.

A bidirectional GPIO pin is required. The 1-wire bus expects to be driven by an open drain. Not many microcontrollers have a true open drain output, but many can be made to work by manipulation of the direction control bit, which puts the output driver into a tri-state high impedance mode when configured for input.

A basic requirement for standard speed 1-wire is the ability to generate accurate and repeatable 1 us delays. The 1-wire bus has 4 basic operations:

• Reset
• Read bit
• Write 0
• Write 1

• previous -- Past work
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