Raspberry Pi Minecraft and Python - create lots of blank worlds to mess about in.

I've been playing with Python and Minecraft on the Raspberry Pi.  Using the API included you can write Python scripts to build in Minecraft.
I like to work with a blank world rather than an existing landscape because the landscape may not work or if I make a mistake it can be hard to undo.

So, I wanted to quickly create a bunch of disposable worlds that I can run my very rough scripts in to see where I need to tweak them.

NOTE: for some reason some flowers and things are left behind. It might be an attribute thing...

Code Below:

#!/usr/bin/python

import sys
import mcpi.minecraft as minecraft
import mcpi.block as block

mc = minecraft.Minecraft.create()

mc.postToChat("Clearing ALL")

blockId = block.AIR.id
mc.setBlocks(-127,-127,-127,127,127,127,blockId)

mc.postToChat("create floor")

blockId = block.DIRT.id
mc.setBlocks(-127,0,-127,127,0,127,blockId)

There are no indents so should just work if cut and pasted to a text file and saved.  I used clearall.py

Start Minecraft
Create a World

RUN:
python clearall.py

The whole world is made of AIR with a 'ground' of DIRT is added at Y=0.
This will take a while to run so be patient.

Now you have one blank world.

But that would be slow to do that every time you need a blank world.

Well with a bit of jiggery pokery you don't have to.
The method I used is probably a bit manual but it is faster than coding for new worlds every time.
Maybe somebody brighter than me can automate it.

Step 1. Make sure you can see hidden folders when browsing on your Raspberry Pi.
The got to ~/pi (if your username is pi)
Open .minecraft/games/com.mojang/minecraftWorlds
This is the directory where your saved Worlds are stored.
One per folder. For me the blank world I created was called world

Create a bunch of new directories. I used world-blank1, world-blank2 etc....
Make as many as you want.

Go into the original world directory and copy all the files.
Then paste those files into each of your world-blank directories.
Now you have replicated the blank world you created with the above script too all of these world maps.

If you go back into Minecraft they will be there. Only problem is they will all have the same name. Not ideal when you want to know which ones you have broken and which are still clean.

This is where it gets a bit more low level but still quite simple.

Installed ghex a gui based hex editor with sudo apt-get install ghex

Then for each folder open level.dat using ghex and find where it says world
Modify the text to a different name making sure to keep it the same size.  Maybe B0001.
Save the updated level.dat.
Do this for each of your new directories making sure to use a different name (B0002,B0003,...) .

If you run minecraft you will get a list of Worlds all with different names.  For me the order was still a bit mixed up but I can live with that.

Finally, rather than having to do this every time I created a new directory under com.mojang called backup-blank and copied all my newly made blank world into that directory.

Now I can mess about with the blank worlds. Building all kinds of strange shapes not caring about  it being perfect as I can just delete that world and replace it with a new clean one by just copying the saved worlds in backup-blank  back into the minecraftWorlds directory and start again.

Note: For me I have 20(ish) blank worlds created as I mess up a fair bit and this usually allows me to do one good session without having to copy across or create a new blank world.

Happy Coding.

Surrey and Hampshire Hackspace evening - 21st February

Last night was another great evening at the Hackspace with more new people coming along which is fantastic.

During the week a kind person contacted the hackspace and offered to donate some test equipment and books.  One of the members offered to go to Croyden and collect the stuff.

some of the donated books and kit

What a great donation. It included many electronics books. Some were of great interest from a nostalgia standpoint but will be great for introducing new concepts to members starting out.The book on the 741 op-amp is a great little read and introduces the fundamentals of analogue signals and circuits in a nice easy but practical way.  Amongst all the books were an lcd projector and an oscilloscope. Both in perfect working order and will be a great addition to the resources the hackspace has for meet-ups and building circuits.


With new blood came new and interesting possibilities. There were great discussions about pic programming in assembly, control circuitry for race cars, home heating automation with a Raspberry Pi at the heart of it amongst other tops.

A real interesting topic was a satellite developed in Surrey that is controlled using a mobile phone.
More details on the University of Surrey website
Below is video showing what is in the satellite, what it does and how it's all put together.

So, the hackspace is going from strength to strength with more people taking part.

Here's looking forward to the next meet-up and some more interesting discussions and demos.

A selection of pictures from the evening. (sorry for the poor quality - mobile phone pics)

Raspberry Pi + GPIO + Scratch + Remote Control Car

At the beginning of 2013 I started a Code Club at my local primary school and the kids love making and playing the games.  Due to the way the club is set up in the school there is expected to be a few classes after the official Code Club sessions are completed so I've been trying to come up with some ideas of things I could bring in to the class to show the kids that Scratch can do more than make a cat move around the screen.

Then on my regular trawl of the web I found this fantastic code http://cymplecy.wordpress.com/2012/08/26/scratch-controlling-the-gpio-on-a-raspberrypi/ for controlling the GPIO pins on the Raspberry Pi using Scratch.

With an old cheap remote control car in a drawer I had the makings of a fun project for me that (hopefully) will be of interest to the kids.

 Having read that the Raspberry Pi GPIO pins are not protected, so one silly mistake on my part could cause the death of my Raspberry Pi I dusted off my old electronics knowledge and put together a small transistor based driver circuit for the 4 pins used.

one circuit per pin

I originally wired this up on a protoboard and it worked, except for when it failed. Did I mention the remote control car was cheap. Well, the aerial was just a bit of wire and with all the other wires I added to the circuit there was regular interference that caused the remote to activate the wrong signal making it unreliable. Knowing the circuit was good the logical thing to do was to put the circuit on a proper board. Rather than going all the way to etching my own circuit board I made it up on a stripboard

again, 1 circuit per pin. white blobs under resistors are cuts in the tracks

After a false start (details of things I almost did wrong) I got the 4 circuits soldered up and tested.  Worked first time.

Not the prettiest soldering but after doing near no soldering for over 20 years I was happy with the result.

Now I the circuit soldered up and it worked. With a bit of coding in Scratch I could program the remote control car for a sequence of actions like
Forward 2 second
Left 0.5 seconds.
Reverse Right 2 seconds

As you'd expect from a simple remote control car the was no way to give very accurate instruction. The motor was either on or off, no variable speed or feedback.  Even with these limitations it felt great when I clicked on the code in Scratch and car actually did what I expected it to do.

the vehicle of my success!!!

And finally he is a short video of the car in action.

This is why I love the Raspberry Pi and the fun of hacking.  With a little bit of effort you can have a lot of fun. Now I have a remote control car that I can control with drag and drop commands in Scratch on a £30 computer.