Subject: Re: Dallas semiconductor "one-wire" and envsys(4)
To: None <>
From: Aaron J. Grier <>
List: current-users
Date: 02/27/2006 15:17:29
On Mon, Feb 27, 2006 at 09:42:53PM +0000, David Laight wrote:
> Is this the same interface as used in some of the battery gauge chips?
> Where you generate a square wave with a 25%-75% duty cycle (for 0 and
> 1), and where the device sends you data at its own clock speed that
> you have to follow and sample the midpoint (or time the high part) to
> work out whether it is sending a 0 or 1 ?
> If so you need a uart to generate the data and parse the response (or
> a dedicated PIC cpu to drive the gpio lines), you won't do it reliably
> from within a Unix kernel without completely stuffing anything else
> the system is trying to do.

why bother with a uart when you can bitbang?


just kidding; I deal with these parts on an embedded target at work and
they are problematic.  the enumeration process is especially awful.

I imagine some ports are worse than others regarding spinning in the
kernel with interrupts masked...

  Aaron J. Grier | "Not your ordinary poofy goof." |
              "silly brewer, saaz are for pils!"  --  virt