8 SLOT BRAMBLE

For the 8 Slot STL, use your favorite slicer to create the files to print.

If you look within Sketchup, the 4 objects closest to the junction of the XYZ axes are all you have to print. The ones obviously for the Pi Zeros (Leaf and Cap) just get printed 8 times. The other two (rails and sides) get printed 2 times. There shouldn't be a lot of cleanup except for removing the brim after the print.

Glue up the mating blocks with super glue, so that the rails are top and bottom and use some blocks and weights to keep them lined up while the glue sets.

A Raspberry Pi Zero will JUST fit inside the fence of the Leaf and the slotted cap is a tight press-fit. It ain't coming out.

MODULAR BRAMBLE

The corner pieces are the ones with the one taller wall and the corner slot. Print those twice. They can flip 180 degrees to be top and bottom corners. They are very tight in the slot and are ideal as walls when you fit a leaf in them: if a leaf is to be a wall and a compute module, you will need to cut into the corner wall where the WIFI dongle would go or solder a usb - ethernet module). The dovetails WILL require cleanup, but will eventually slot into each other. I designed the dovetails so there is only one way to connect.

The rails for the middle Zeros are designed to simply print twice for top and bottom.

Install a known working wifi dongle by sticking in a USB OTG converter into the plug-in of the dongle.

Slot in an SD card that has been loaded with a Raspberry Pi (not Pi 2!) image that has SSH server available. Power up the Zero and run a scan on your network to find the new computer.

SSH into the computer and start configuring for clustered computing.

Once you have a Case you are happy with, build a cluster image for your Pi Zeros. If you follow the Instructable that Gigafide put together recently, you will be okay. Here is a line-by-line rundown to get the common image (before you have to go between node and head)

Install Jessie via NOOBS (you can get this from raspberrypi.org)

Install all extra packages needed for clustering and SSH, by using the following:

sudo raspi-config

Install image onto at LEAST a 4 GB sd card. For my setup, I will be using a 32GB card for the data, and 16GB cards for the head and nodes (leafs)

Hostnames will be:

rpi0

rpi1

rpi2

IP addresses in this case are 192.168.1.50[51 & 52]

For now, I will be using my home router, and later on will have a different subnet from my home subnet. I will be configuring the head to allow users from within my home network to connect to the head.

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INSTALL MPICH MASTER

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sudo apt-get update && sudo apt-get upgrade

mkdir mpich2

cd ~/mpich2

wget http://www.mpich.org/static/downloads/3.1/mpich-3.1.tar.gz

tar xfz mpich-3.1.tar.gz

sudo adduser mpi_user

sudo mkdir /home/mpi_user/mpi-install

sudo mkdir /home/mpi_user/mpi-build

cd /home/mpi_user/mpi-build

sudo apt-get install gfortran

sudo /home/mpi_user/mpich2/mpich-3.1/configure -prefix=/home/mpi_user/mpi-install

sudo make

sudo make install

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SETUP ENVIRONMENT

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nano ~/.bashrc

PATH=$PATH:/home/mpi_user/mpi-install/bin

sudo reboot

mpiexec -n 1 hostname

The above should return the hostname value of the head node.

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SETUP PYTHON TO MPI INTERPRETER

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sudo aptitude install python-dev

wget https://mpi4py.googlecode.com/files/mpi4py-1.3.1.tar.gz

/* YOU WILL GET SOME WARNINGS HERE */

tar -zxf mpi4py-1.3.1.tar.gz

cd mpi4py-1.3.1

sudo python setup.py build

sudo python setup.py install

export PYTHONPATH=/home/mpi_user/mpi4py-1.3.1

mpiexec -n 5 python demo/helloworld.py

since you're here now, you may as well create a file in the mpi_user home called machinefile. Populate it like this:

rpi0

rpi1

rpi2

At this point, you will be ready to create a common image. Now, here I disagree with the author, because he would have already expanded the filesystem in one of the first steps. I say, use a 4 GB SD card to make the minimal image, then copy, THEN expand the filesystem.

Follow the instructions on this link to get both the wired and wireless interfaces to work at the same time. I never knew that plugging in one would disable the other...

First, backup your network settings:

for i in `/etc/network/interfaces /etc/wpa*/wpa*`;do cp $i > $i.orig;done

Basically, edit your /etc/network/interfaces file to look like this:

source-directory /etc/network/interfaces.d

auto lo

iface lo inet loopback

auto eth0

#iface eth0 inet manual

iface eth0 inet static

address 192.168.1.50

netmask 255.255.255.0

broadcast 192.168.1.255

gateway 192.168.1.1

allow-hotplug wlan0

iface wlan0 inet manual

wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

allow-hotplug wlan1

iface wlan1 inet manual

wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

IF YOU'RE USING WIFI USE THE BELOW EXAMPLE

source-directory /etc/network/interfaces.d

auto lo

iface lo inet loopback

auto eth0

iface eth0 inet manual

allow-hotplug wlan0

#iface wlan0 inet manual

iface wlan0 inet static

address 192.168.1.52

netmask 255.255.255.0

broadcast 192.168.1.255

gateway 192.168.1.1

wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

allow-hotplug wlan1

iface wlan1 inet manual

wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

-------------------------------------------

And your /etc/wpa_supplicant/wpa_supplicant.conf, like this...

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev

update_config=1

network={

ssid="YOUR_ESSID"

psk="YOUR_NETWORK_PASSWORD"

}

-----------------------------------------------------

edit your /etc/hosts file

127.0.0.1 localhost

192.168.1.50 rpi0

192.168.1.51 rpi1

192.168.1.52 rpi2

Once you have your basic networking setup and checked out, it's time to move on the the meat and potatoes of this whole operation: SSH key-sharing. I'll warn you ahead of time; if you finish and during testing you get a key verification failure, you made a mistake during the key-share process.

MASTER NODE

log in as mpi_user

cd ~

ssh-keygen (take the defaults)

cd .ssh

cp *.pub $HOSTNAME

ssh mpi_user@192.168.1.51

ssh-keygen

cd .ssh

cp *.pub $HOSTNAME

scp 192.168.1.50:/hpme/mpi_user/.ssh/rpi0 .

cat rpi0 >> authorized_keys

exit

ssh mpi_user@192.168.1.52

ssh-keygen

cd .ssh

cp *.pub $HOSTNAME

scp 192.168.1.50:/hpme/mpi_user/.ssh/rpi0 .

cat rpi0 >> authorized_keys

exit

scp 192.168.1.51:/home/mpi_user/.ssh/rpi1 .

scp 192.168.1.52:/home/mpi_user/.ssh/rpi2 .

for i in "rpi1 rpi2";do cat $i >> authorized_keys;done

I didn't script the last 2 scp commands because if this is a brand new build, you will get prompted for passwords, and answer a request to transfer keys (haven't figured that part out why yet).

Given enough time, I will script this whole thing out for minimal hands-on, but for the purpose of this project, this works.