PS3 Setup

We generally use one of three methods to shut the Raspberry Pi down:

1. Simply pull the plug:
   While not ideal it does not tend to cause problems, you will have the same effect if the batteries become flat
2. Shutdown via SSH:
   Fairly simple, does require either a wire or wireless network connection to the DiddyBorg though
3. Add a button press to the script(s):
   This is easy to add in, we use select for this normally

If you wish to add a shutdown button to the script you will need to add the two highlighted sections below.
The line numbers / code lines are based on diddyJoy.py:

# Settings for the joystick
axisUpDown = 1                          # Joystick axis to read for up / down position
axisUpDownInverted = False              # Set this to True if up and down appear to be swapped
axisLeftRight = 2                       # Joystick axis to read for left / right position
axisLeftRightInverted = False           # Set this to True if left and right appear to be swapped
buttonResetEpo = 3                      # Joystick button number to perform an EPO reset (Start)
buttonSlow = 8                          # Joystick button number for driving slowly whilst held (L2)
slowFactor = 0.5                        # Speed to slow to when the drive slowly button is held, e.g. 0.5 would be half speed
buttonFastTurn = 9                      # Joystick button number for turning fast (R2)
interval = 0.00                         # Time between updates in seconds, smaller responds faster but uses more processor time
buttonShutdown = 0                      # Joystick button number to get the Raspberry Pi to shutdown (Select)

# Power settings
voltageIn = 12.0                        # Total battery voltage to the PicoBorg Reverse
voltageOut = 6.0                        # Maximum motor voltage

                # Check for button presses
                if joystick.get_button(buttonResetEpo):
                    PBR.ResetEpo()
                if joystick.get_button(buttonSlow):
                    driveLeft *= slowFactor
                    driveRight *= slowFactor
                if joystick.get_button(buttonShutdown):
                    # Start the Raspberry Pi shutdown sequence
                    print 'Shutting down...'
                    PBR.MotorsOff()
                    PBR.SetCommsFailsafe(False)
                    PBR.SetLed(True)
                    os.system('sudo halt')
                    break
                # Set the motors to the new speeds
                PBR.SetMotor1(driveRight * maxPower)
                PBR.SetMotor2(-driveLeft * maxPower)

Now when you press select on the controller:

1. The motors should stop
2. The LED on the PicoBorg Reverse should come on
3. The Raspberry Pi starts to shutdown
4. The script terminates
5. The Raspberry Pi indicates it has finished shutting down

You can find the PS3 button numbers on our PS3 controller setup instructions page if you wish to use a different button.

We used starter motors, however you could equally use motors intended for:

• Electric scooters
• Powered wheelchairs
• Mini ATVs

We simply picked something we could get six of with a decent amount of power (W).

If they are connected in the same way we have they should all be the same.
If they are not it is very likely the "slower" motors will be pulled by the "faster" ones, which is very inefficient.

We did not actually try four motors, but I suspect the steering may struggle.
When he turns the middle two wheels do most of the work, the front and back are mostly just "breaking traction".
You could try removing the centre motors from DiddyBorg to see how he copes, carpet would make a good approximation of rough ground.

We made the gearing high for two reasons:

1. Increased torque, which allows us to pull more weight
2. He is scary enough at full speed as it is, lower gearing would make him move faster

If you take the RPM of the motor and your wheel measurements you can work out the theoretical top speed of the wheel.
This theoretical top speed is a bit above how fast the wheels should go when lifted off the ground, the heavier your robot is the further his real top speed will be below this value.
You can then take this number and work out a reasonable gearing ratio.

Our aim with DoodleBorg was raw pulling power :)
It would be great to see another large Raspberry Pi robot, especially if it has something special about it.
The main problem we had was expense, mostly because of the heavy weight he moves around.
If you make a lighter one you would be able to get away with lower power motors with lower gearing.

Thanks for the photos, I think your Velcro battery strap is a great idea.

Depending on how slow you will make the robot you may find windscreen wiper motors are a bit too heavily geared internally.

With regards to how much power it all depends on how heavy the robot is overall.
With the weight we have I would imagine 200 W each would have probably sufficed if we did not care about towing.
The awkward point is that more powerful motors also tend to be a bit heavier.

An important consideration is where you intend to actually run the robot.
In our case DoodleBorg is too big and fast to really run around your average back garden.
In truth we actually find it quite hard to find places we can run him freely, usually we resort to empty car parks and similar places.
If you make a smaller one (say 1/2 the size) you will find more places to be able to run.

Since both size and weight limits will reduce the available options for motors I would suggest you get a rough idea of how big and heavy you want him to be quite early.

The LEDs are a great idea.
You may need to do some threaded code in Python so that the LED operation and movement operation run along side each other, but it should not be too difficult to have both in the same script.

Wow, that is dedication!
Since we do not have a face to go with your name let us know who you are when you see us.
Hopefully we will be obvious enough from the mixture of robots and a near table heigh logo :)

To get Python code to show up in the forum with line numbers and highlighting you can surround it like this:

<pre class="brush:python">
Line 1
Line 2
...
Last line
</pre>

If you are starting from a line other than 1 you can do this instead:

<pre class="brush:python; first-line: 5;">
Line 5
Line 6
...
</pre>

You should be able to highlight lines in Putty when Nano is open using the mouse (left-click and drag).
This will copy the highlighted text, you should then be able to paste it into the forum text-box.

The switch is an awesome edition, clever thinking with using the posts to take the force.

I find having a good text editor makes coding a lot quicker, but there are so many to choose from.
Personally I use Vim / gVim as my main text editor on both Linux and Windows.
It is probably too scary / advanced for most users as it requires you to remember which keys do what (and there are a lot of them).
Even for advanced users it will not be to everyone's taste.

For Windows I have a fairly easy recommendation here: Notepad++.
It is still simple to use like Notepad or Nano, but it packs a ton of features in, including line numbers.

For Linux there are several editors in the graphical environment which fit nicely:

• Geany - Offers some nice features such as listing the functions in a script
  If it is not already installed you can install it with sudo apt-get -y install geany
• LeafPad - Similar to Notepad
  Very simple editor, but it come with line numbers and is installed by default on Raspbian.
• gedit - The standard GNOME editor, similar level of functionality to Notepad++
  Install with sudo apt-get install gedit
• Kate - a standard KDE editor, similar level of functionality to Notepad++
  Install with sudo apt-get install kate

The Linux terminal based editors are a little more tricky, so I will divide them into sections.
Installed by default on Raspbian:

• Nano - Fairly friendly but fairly limited as well, does give syntax highlighting
• Vi - Advanced editor too complicated for beginners, personally I would try Vim instead since it offers the same functionality plus a massive list of improvements

Intermediate editors:

• JOE - Similar type of interface to Nano but with more powerful options
  Install using sudo apt-get install joe
  You can see line numbers if you use joe -linums filename
• ne Nice Editor - Operates from a mixture of key presses or menus
  I cannot find a show line numbers option, but the status at the bottom shows current line and there is a "Goto line" option (Either CTRL+J or ESC → Search → Goto line).
  Install using sudo apt-get install ne

Advanced editors:

• Vim - powerful editor that can be heavily customised, commands are based on multiple key presses
  Install with sudo apt-get install vim
  Alternatively use sudo apt-get install vim-gnome, this will also install gVim for the graphical environment
• Emacs - powerful editor that can be heavily customised, commands are based on key combinations with CTRL, ALT, and ESC
  Install with sudo apt-get install emacs