Pi Projects (generally no soldering iron required)

The Register has done its homework and come up with some of the easy Raspberry Pi construction projects.

• Coffee table arcade game
• LAMP server (that is Linux, Apache, MySQL, and PHP, and server as in a computer server)
• Pi/Kindle Chimera
• Pi Netbook
• Info kiosk info projector
• Weather station
• Cloud server
• Pi scales
• Pi-BX

The projects are summarised on www.theregister.co.uk.

Python and Minecraft on the pi.

Right, first for a copy of Minecraft: Pi Edition visit pi.minecraft.net/. And background information on Minecraft on the raspberry pi; see www.raspberrypi.org).

Copy the file (e.g. minecraft-pi-0.1.1.tar.gz) into your home directory.
Expand it; I used the tar -xvf command to unpack the gzipped and tarred up distribution.

tar -xvf minecraft-pi-0.1.1.tar.gz
cd mcpi
./minecraft-pi

And this starts Minecraft from the xterm.
At this point you can play Minecraft as you would expect on any conventional computer.

Now for the spice; using Python to send commands to directly to Minecraft, taking command of or interacting with the environment.

Well Python comes with the Raspbian “wheezy” Linux distribution for pi. It's already there waiting for me.
Following instructions from numerous other early explorers (best and most interesting for beginners I judge to be that by prmrytchr).

From a new xterm and staring in the mcpi directory...

cd api/python/mcpi/

Then start Python, and tell Python to import the minecraft.py functions and connect to my local running Minecraft session. My xterm looked like this.

Python
Python 2.7.1 (r271:86832, Jul 31 2011, 19:30:53)
[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import minecraft as minecraft
>>> mc = minecraft.Minecraft.create()

The >>> indicates that the Python session is running so now I can type in some of the suggested Python instructions.

>>> mc.postToChat(“Hello, Minecraft!”)

And I see the message display in my running Minecraft game.
I can get the game to report my player position...

>>> mc.player.getPos()

Even if my player is at the spawn point I should probably can use this position (x,y,z) to do stuff. Like this to place a mushroom at the coordinates...

>>> mc.setBlock(x,y,z,40)

Now from Ger a quick command to test set all the numbered block types in sequence.

>>> for i in range(50):
>>> mc.setBlock(i, 53+i, 25, i)

Useful links for further progress
www.minecraftwiki.net beginners guide
www.minecraftwiki.net tutorial
www.stuffaboutcode.com
A maze generator: www.jonasavrin.com

And when you've finished shutdown X to the console then type sudo shutdown

Writing the Raspbian Pi image to an SD card.

My pi!

So, downloaded Raspbian “wheezy” (link). 493.6 MB.

Check the checksum in an xterm:
shasum ./2013-02-09-wheezy-raspbian.zip
b4375dc9d140e6e48e0406f96dead3601fac6c81  ./2013-02-09-wheezy-raspbian.zip

Which is the same as the published checksum
SHA-1 Checksum: b4375dc9d140e6e48e0406f96dead3601fac6c81

and unpack the file (2013-02-09-wheezy-raspbian.zip), again, from the xterm:

unzip ./2013-02-09-wheezy-raspbian.zip
Archive:  ./2013-02-09-wheezy-raspbian.zip
inflating: 2013-02-09-wheezy-raspbian.img

On the Mac I followed elinux.org's instructions for "Copying an image to a 4GB SD card in Mac OS X (command line)". They seemed to be the most accurate and complete (link).

The following pointers apply to a computer with an external USB SD card reader. I my case I used the Puremedia SD USB Card Reader product.

Inferring the device id for the SD reader:

From 'About this Mac' click on System Report. Select Hardware>USB. One of the USB High-Speed Bus entries will reflect the details of whatever SD card is currently loaded. Eject and reinsert a couple of times, reloading the System Report between each state to verify that you are referring to the correct entry. This is important because you can wipe hard disks with incorrect disk duplication commands.

In my case I had an SD card with the following details:
  Volumes:
NO NAME:
  Capacity: 78.6 MB (78,643,200 bytes)
  Available: 48.3 MB (48,336,896 bytes)
  Writable: Yes
  File System: MS-DOS FAT32
  BSD Name: disk2s1
  Mount Point: /Volumes/NO NAME
  Content: Windows_FAT_32
disk2s2:
  Capacity: 1.67 GB (1,667,235,840 bytes)
  BSD Name: disk2s2
  Content: Linux
disk2s3:
  Capacity: 200.3 MB (200,278,016 bytes)
  BSD Name: disk2s3
  Content: Linux_Swap

What this means, in MY CASE ONLY, that the device name (and therefore the 'raw device name') is disk2 (or rdisk2 for its raw equivalent). In this particular case the BSD names (e.g. disk2s1, disk2s2, disk2s3) are volumes or partitions on the SD card I was using. They will probably all disappear after following the disk image copying instructions. The reason I had these extra volumes on my SD card is that I was practicing disk imaging/partitioning on it.

I replicated the process from an xterm using the df -h command. Same result.
So starting with the SD card inserted and mounted, unmount it using sudo diskutil unmount /dev/disk2s1 (my case only). The icon will also disappear from the desktop confirming this step was successful.

The last step is to write the raspbian image file to the raw SD card device as identified above, replacing disk2s1 with rdisk2:
sudo dd bs=1m if=./2013-02-09-wheezy-raspbian.img of=/dev/rdisk2

After anywhere from 3 to 5 minutes the disk image write finishes. The xterm looked like this:
1850+0 records in
1850+0 records out
1939865600 bytes transferred in 226.104953 secs (8579492 bytes/sec)

And there's a shiny new disk labelled 'Untitled' on the desktop. At first impression it looks like your 4G sized disk has tragically shrunk to 58.7 MB. The reason is that the SD disk now has a Linux swap partition and a Linux file system partition occupying the available space. The good news is that most of the slack space can be recovered the first time you load this SD card on the Raspberry Pi via one of the Pi configurator (raspi-config) options to reallocate the space from the linux partition to the FAT32 partition.

I plan to duplicate the process on Windows to verify the approach.

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