[Weather] NSLU2 (SLUG), OWFS vs OWHTTPD, owwnogui, and the 1wire Weather Stations

[Steinar Midtskogen]

> I've finally got my SLUG operational (unslung 6.8) and de-underclocked.
> Now I'm mulling over different ideas on how to pull the weather station
> (and other 1wire) data from my SLUG and do something useful with it. I'm
> wondering if anyone else is using the owfs/owhttpd approach, or if you
> are all using owwnogui. I'd be interested in the reasoning for your
> decisions regarding one vs. the other.

I'm using owwnogui for my weather station, but I'm setting up another
slug which will use owfs to control an AAG switch and an LP-THS
connected to it.  The reason why I go for owfs for the latter is
mainly because owwnogui doesn't support the switch, and because I will
use it in custom scripts.  It will be used to monitor the water
pressure to my house and to control the water valve.  It will close
the valve in the event that the temperature gets too low, and it will
make pressure tests: close the valve for a while at night and check
whether the pressure is dropping (which would indicate that there's a
leak somewhere).  For these things owfs seems to be the right choice.
It's not up yet because I'm waiting for OpenSlug 4.0 and a 2.6.17+
kernel so that I can get my USB wireless adapter to work.

> So what do you guys think? Push or pull?

I actually perfer to store data on the slug, so I don't have to rely
on a working network and another computer.  Otherwise I could just as
well have connected the 1-wire bus to that computer.  You can store a
lot of 1-wire data even on half full 1 GB flash drive.  You can still
pull or push data, but I think that choice is secondary.

I use one slug for capturing pictures from a digital camera and it
will fill up 1 GB in less that two days.  In this case I store locally
on the slug, but I'm using another computer to pull and delete.  If
the computer or network fails, I'll have two days to fix it before
I'll lose data.

I like the idea that the slug works indepentently.

As an extra securety, in case a slug freezes, I'm using another slug
as a watchdog, which will cut the power to it and restart (using the
sis-pm, a programmable outlet strip with a USB interface).  This
assumes that the slug has been modified to boot at poweron.

Yet another security measure that I've added, is to have the slugs
boot from a raid1 array of flash cards.  If one flash card fails, it
will still run, and it can easily be replaced without downtime.

If it still fails, it should be possible to set up a new slug in
minutes.  A regular computer used for pull/push is much more
cumbersome to replace and reinstall.

-- 
Steinar