Raspberry PI, Openelec and 1-wire temperature sensing

I've finally got back to writing up some blogs, so there are a few things I'm currently trying to achieve, and as always the solution to a problem involves Arduino, Raspberry PI and electronics!

This particular problem is my home heating system. After being in the new house for a year we're still struggling to have the heating system actually heat the house to a comfortable amount when it needs it. The built-in heating system uses a temperature sensor (Looks like a DS18B20) in the hallway (beside front door and a radiator), and most other rooms have radiator thermostats. The problem is that the hallway never really matches the temperature in the rest of the house, bedrooms are often cold and other rooms roasting hot. Therefore I had a plan to have temperature sensors around the house and provide an 'overview' on/off to the heating system, in theory when rooms are still too cold, forcing the heating to stay on should let these rooms warm up and rooms that are already up to temperature will remain there because of the radiator thermostat. So to do this I need a way of sensing temperatures.

I already have Raspberry PI's in a few of the rooms, sat behind TV's to provide TV/media playback, so I looked into using the 1-wire temperature sensor DS18B20 on the PI. Now luckily there is a nice 1-wire kernel module available so it's pretty easy, modprobe the 1-wire module, modprobe the 1-wire temperature module and you can then pull sensor values using a script. Pretty easy, and yep testing this it works great.
The commands used were simply:

modprobe w1-gpio

modprobe w1-therm

Which then allowed me to grab sensor values by prodding about in the '/sys/bus/w1/devices'

However, I use Openelec, not a standard Raspbian release. Now Openelec is great, it's a cut-down system that just works, it boots quickly and runs the hardware nicely. But because it is cut-down for speed a lot of modules, etc, have been removed, and in this case the 1-wire modules have been removed.
So I needed to get a solution to provide the modules in Openelec. To do this I needed to recompile it, which I didn't find the solution to very easily, so I've documented it here not just for myself but in case anyone else wants to try this. First you need the Openelec build environment, so clone their github repo:

git clone https://github.com/OpenELEC/OpenELEC.tv.git

You then do the initial build by running:

PROJECT=RPi ARCH=arm make release

And leave it (This took my server about 5 hours to complete). That gets you the same release that you're probably running now from the downloaded Openelec/official release. Now to custom the kernel, so you do:

PROJECT=RPi ARCH=arm ./scripts/unpack linux

Which then allows you to edit the kernel parameters like normal, so then running:

cd build.OpenELEC-RPi.arm-devel/linux-3.19.0

Followed by:

make menuconfig

Gets you to change kernel parameters. The changes I made were fairly simple, just:

CONFIG_W1=m
CONFIG_W1_MASTER_DS2490=m
CONFIG_W1_MASTER_DS2482=m
CONFIG_W1_MASTER_DS1WM=m
CONFIG_W1_MASTER_GPIO=m
CONFIG_W1_SLAVE_THERM=m

Adding those you can then recompile the kernel again like this:
make menuconfig
cp .config ../../projects/RPi/linux/linux.arm.confPROJECT=RPi ARCH=arm make release

And you're done. Copy the produced KERNEL and SYSTEM files (in the target folder) over to your PI in the /flash partition and boot up, should be all working at that point.

You can then connect the 1-wire sensors up and start to pull values. I'll add that to the next blog entry on how to connect the hardware and then start to retrieve the values.

(Edited: 22/05/2015 thanks to Chris Van Marle pointing out some stupid errors of mine!)