Over the last couple of weeks l’ve done a bit more work on my HomePi project. I have now finished the design of the pcb (for the first version). Previously i had been using Eagle to design my pcb’s, this time however i have used Fritzing instead.

While Eagle is very good, its also a bit hard to use, especially if you have not done a lot of electronics work before. Fritzing on the other hand is aimed at novices and is very easy to get to grips with. You can create a virtual breadboard of your project, and based on this it will create you a real schematic and a PCB. There are also loads of template part available online, so building up the project is a simple! Check out the software at http://fritzing.org/.

They also offer a PCB fabrication service, but it doesn’t work out as cheap as using Seedstudio, although (from a European standpoint)  you will end up with your board a lot faster. This is an export of my breadboard view:

So, on this board I have the following sensors:

• A DHT11 temperature and Humidity sensor
• A light resistor and capacitor for measuring the current light level
• An LED that can be turned on or of (to be used as a lego street light that comes on at night)
• An Rj45 interface so the device can be extended with 1-wire devices

My HomePi board will be mounted on the top of an Adafuit LCD pi plate using a 45° GPIO header. The LDC plate will have the LCD screen plugged in, and is mounted in the roof of the Lego house. My first (unfinished version) of this is pictured below:

From the  Fritzing software, I have also printed out the PCB, backed it on a some polythene packing sheet and mounted all the components on it. I have done this to give me a rough idea of how big the finished PCB will be, and to make sure its going to fit in the house OK. Lucky it looks to be the right size:

 
So hardware wise, I think I am now ready to get my board made. I still need to do some more work on the actual house, one of my main things with the house is i’m not sure the best way to create my little street light. I have ordered a pre-made Lego street lamp, so I might have to drill some holes in it to get my LED in.

Software wise, I have done a bit more work on the Python script that controls everything. I have tided up some of the code, and it is now hosted on Github, so you can download it yourself and have a play around. At the moment there is no instructions on how to build everything needed for the code to run, but as I need to build an sd card from scratch for the micro sd adapter I am going to use, I will document it as I build. Go and grab the python script now from https://github.com/beakersoft/HomePi

As I mentioned in the previous post, I am building a little Lego house with a raspberry pi inside it that is going to drive an LCD screen and output some interesting information. I now have most of my hardware parts working on a breadboard, and I am displaying text on the LCD screen.

So far its doing the following, all via a python script:

• Show the current date and time on the LCD screen
• Read the temperature and humidity from the sensor, and display on the screen
• Show the current twitter trends on the LCD screen
• Using the light sensor, if the light level is below a certain level (ie its dark) then turn off the LCD screen, and turn an LED on. When the light level returns back to normal, turn off the LED, turn the LCD screen back on and start looping through the date/temp/twitter information again

I have mounted the Adafruit LCD breakout board on an extra long GPIO header, so I can still use the pins on the pi. Instead of attaching the LCD screen directly to the breakout board I have connected it via cables, this is so the Pi can sit at the bottom of my lego ‘house’, and the LCD screen can be put in the roof.

The actual python script needs a couple of tweaks  then I will upload it onto Github so anyone can have a play with it. Its quit simple, but someone might find it useful.  The next things i need to do are:

• Work out the best way of putting a 1-wire connector (probably Rj45) onto the system, so a new sensor can be easily added to the new system.
• Try and work out if  the new Pi camera  module will fit into the system somehow
• Design an actual pcb for the system to mount the components on. Everything is on a breadboard at the moment, obviously this cant be used in the finished house. Seedstudio offer quite a good pcb prototyping service, hopefully I can use them. I also need to work out the best way to mount the pcb to the pi, in the house.
• Build the actual lego house to hold it all in. I looked at the LEGO Digital Designer software, but I have decided to do it old school and just try and build it from scratch.
•  Look at some sort of back end to the system, probably web based so it can be configured easily and some of the data can be logged.

Once I have the script on Github I’ll post a link on here

After quite a while waiting, today i finally managed to get my hands on a raspberry pi!

They have been all over the media recently, but in case you have been living under a rock, the ‘pi’ is a cheap, small ARM based computer. When I say cheap i mean cheap. $25 + tax + shipping. When I say small, i mean small, this thing is just slightly larger than a credit card, and weighs next to nothing. For your $25 all you get is the board, there’s no power supply, no cables, no SD card, just the board. Its a proper hackers bit of kit, and the fact that this thing is so cheap kind of makes it throw away.

The possibilities for this thing are huge, its (very commendable) target market is school kids, trying to get them back to the home game hacking ways of the 80′s, but it has so many other uses, especially considering you can fairly easily extend the hardware and use it to drive other devices. Hopfully as I get to grips with it I will post more info on here, but for the meantime enjoy some (rather sad!) pictures of me un-boxing the device!

Quick Note: The first time I booted to the desktop the display did not fit very well on the screen, follow this tip on the pi forums and it should help you out