I wrote this a few weeks ago and forgot to post it.
I received a Raspberry PI recently. It looks great, nice and small.
I have been playing with PlugComputers, such as the SheevaPlug and the Seagate Goflex series for a few years. They form the basis of my low power computer systems that are on 24x7. The Raspberry PI is just like one of them but with a few extra facilities.
Getting up and running was a breeze. I simply downloaded the image, by bittorrent, if I remember correctly. It only took a few minutes.
I blew it onto an SD card and powered it up. Hey Presto! it worked. I was able to determine it's IP address and ssh in to have a look around. Perfect.
I didn't have a HDMI cable to hand, so I used a composite cable to connect it to the TV. It worked but the quality was not the best. Moved on.
I was wondering what to use the PI for. I still don't know.
I came across an article talking about using the PI with OWFS. http://raspberrypi.homelabs.org.uk/
OWFS stands for One Wire File System. 1-Wire is a technology developed by Dallas Semiconductor (Maxim-IC), that actually uses 2 wires to communicate with devices such as temperature sensors, switches, voltage detectors, a/d converters and so on. I use it extensively throughout the house to measure temperature and control things. One of the great things about the 1-Wire devices is that they are pretty cheap.
On the Raspberry PI, there are a number of input/output pins. The ones of interest in relation to 1-Wire stuff are the I2C pins. I2C is basically a serial protocol. It is the building blocks that USB and SATA are built on.
The good thing is that Maxim-IC make a number of I2C to 1-Wire controllers. These are the DS2482 and DS2483. There are probably others also.
So, the possibility to connect the chips directly to the PI was real.
I was able to acquire a couple of DS2482s from a friend of mine. I had to mount them on a 16 way SOIC to DIP converter.
The OWFS system was easily compiled from source on the Raspberry PI and installed.
I then began the search for the I2C drivers.
This was a hard one. I found many forums that resulted in a dead end. Many kernels were compiled and failed. I couldn't get/build a kernel
that would work with the drivers installed.
I found a fella that had a pre-built kernel built for Debian. I
use Arch, which is pretty different in it's config, even though it is Linux.Here is the link I used http://www.bootc.net/projects/raspberry-pi-kernel/ I also installed the latest firmware.
Anyhoo, I was able to install the new kernel and modules and boot a
workable system. Cool.
All the quick checks were good.
I then wired up the chips, DS2482, and started the main program
owserver. Hey presto, it worked.
I wired a couple of DS18B20's and could see them and read temperatures.
I love this embedded Linux crap.
Thursday, July 5, 2012
Raspberry PI 1-Wire I2C OWFS
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