Why use I²C to access 1-Wire from Raspberry Pi?

A friend of mine asked the excellent question on why I bought an I²C 1-Wire expansion module for 300 SEK (about €30) when there are kernel drivers for using 1-Wire over GPIO right away and exposing the 1-Wire network below /sys/bus/w1/. I honestly didn’t know of this option!

Now I’ve made some investigations and realized that for example the DS2406 1-Wire chips I already bought are not yet supported by the kernel. There is a patch, for those who like to compile their own Raspberry Pi kernel. I don’t.

Also, OWFS seems to do an OK job of hiding the way of interfacing the 1-Wire network, so as long as use OWFS to access my 1-Wire stuff I should be able to switch to the w1 kernel drivers in the future.

For now, I will continue to use the I²C 1-Wire expansion module, because it works fine, I already bought more than one of them (!), and all my stuff is supported.

Home automation with 1-Wire and Raspberry Pi

Me and my wife recently bought a cottage half an hour’s drive from where we live.

She is enjoying herself immensely with interior decorating, grinding floors and mowing the lawn. She is also looking forward to washing and painting the windows and exterior walls…

Naturally I will also do some work on and around the cottage. I use to say that I’m only handy when forced to, but that’s not entirely true… 🙂

Now for the fun part. I have taken on to implement home automation for the cottage. At start it will be mostly monitoring temperature, measuring electricity consumption and checking door and motion sensors.

The heart of the home automation is a Raspberry Pi running Rasbian. On the Raspberry Pi I have mounted an I²C 1-Wire expansion module and installed owfs.

My main sources of 1-Wire hardware is the special interest Swedish web shop m.nu. For other stuff I use the Radio Shack of Sweden: Kjell & Company, and, of course, eBay!

This is a list of some stuff I bought on eBay for various parts of this project. Prices provided in case want to compare to ordinary web shops… 🙂

  • 10 × PIR motion sensors, $12.59
  • RJ45/RJ11 cable tester, $2.91
  • 100 × RJ11 plugs, C $4.33
  • RJ45/RJ11 Crimp Tool, GBP 4.99
  • NoIR camera module for Raspberry Pi, $28.49
  • 2 × Infrared lights for NoIR camera module, $9.49
  • 9800mAh DC 12V rechargeable Lithium-ion Battery, $27.53
  • Micro USB splitter charge cable, GBP 1.49
  • 20 × magnetic door/window sensors, $17.12

So, what is all that stuff good for? My plan is to make a series of posts about the various parts of the project, but I make no guarantees… 🙂

Disable some useless stuff in Raspbian

I’m currently running three Raspberry Pi projects, with Raspbian as my choice of distribution. One of the machines will be co-located at FS Data and run ownCloud. The other will be handle switching a central heater between oil and electricyty via SMS. The third is a surveillance camera heavily inspired by Dummy camera made smart with Raspberry Pi by my talented colleague Tomas Bjerre.

While examining the default Raspbian image I noticed there were some things I will never use, so I disabled them to free up some RAM:

  1. Disable the consoles by putting a # in front of all lines containing /sbin/getty in /etc/inittab:

    #1:2345:respawn:/sbin/getty --noclear 38400 tty1
    #2:23:respawn:/sbin/getty 38400 tty2
    #3:23:respawn:/sbin/getty 38400 tty3
    #4:23:respawn:/sbin/getty 38400 tty4
    #5:23:respawn:/sbin/getty 38400 tty5
    #6:23:respawn:/sbin/getty 38400 tty6
    #T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

    If you get into network issues and need the console you can always mount the SD card on another machine and edit the file there!

  2. If you don’t have a keyboard connected or otherwise don’t want global hotkeys, disable the triggerhappy global hotkey daemon:

    sudo update-rc.d triggerhappy disable

  3. If you have Transmission installed but is not using UPnP, disable the minissdpd daemon for keeping track of UPnP devices:

    sudo update-rc.d minissdpd disable

  4. If you run Apache, disable modules you don’t use. Maybe:

    sudo a2dismod dir
    sudo a2dismod cgi
    sudo a2dismod negotiation
    sudo a2dismod autoindex
    sudo a2dismod setenvif