Subject: Dallas semiconductor "one-wire" and envsys(4)
To: None <>
From: Jeff Rizzo <>
List: current-users
Date: 02/25/2006 09:48:57
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(I debated whether this was more appropriate for current-users or
tech-kern, and decided more potential _users_ would be reached on
current-users.  If more discussion of details is warranted, it should
probably be had on tech-kern)

I'm currently working on a driver for one-wire devices (such as the
DS18B20 temperature sensor) which attaches to gpio(4), and I'm wondering
if anyone else would find this useful - my intended usage is to hook up
a bunch of these devices to a soekris 4511 to monitor various stuff
around the house.

It's not clear to me whether this would be something appropriate to
bring in to NetBSD or not - these devices are not commonly built into
motherboards, and the usual usage is with microcontrollers (PIC, AVR,
etc) - the bus protocol is such that the driver I've written has
DELAY()s of up to 450ms, and I don't see a way to get rid of them and
still retain the correct timing for bitbanging the protocol.  That said,
the chips are fairly inexpensive (the DS18b20 is about US$5 in quantity
1, the DS1822 less than US$4), and are easy to connect up for any
moderately competent hobbyist.

So, on to the questions.

1)  Are people interested in having this available in NetBSD? Is it

2)  Should I do the work to integrate the temperature sensor parts into
the ensys(4) API?  Right now, most of the actual work is done in
userland, with the exception of the bus-scanning code to see what
devices are connected.  If people aren't interested in general (or think
it's a bad idea), I'll probably just leave things this way, because I
don't have particularly complex needs right now.

3) Does anyone have any further suggestions?  The code is currently
"working", though I don't do much with it yet.  If people are
interested, I can clean it up and post it for testing.  (It definitely
needs work before I'm letting _anyone_ see it)



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