You will find out how to add bump switches to your Marty and how to use them in different ways such as avoiding obstacles and knowing when to kick a football!

How do you connect bump switches to Marty? How do you use them?

This activity shows how bump switches are added and, through example code, gives you a taster of different ways that bump switches can be used

This activity gives instructions on how to add bump switches to Marty. It then explores examples of different ways that bump switches can be used and full example code is provided,

Bump switches (sometimes called snap-action switches or limit switches) give Marty the sense of “touch”. Like all switches, they are devices used to make or break connections in an electric circuit.

In robotics, bump switches can be placed on the outside of the robot allowing it to respond to the environment. When a bump switch is pressed, usually due to the robot coming into contact with (or “bumping” into) something, it completes an electric circuit and sends a signal to the control board.

Bump switches can be used for all sorts of things in robotics! Some uses include:

Detecting when Marty walks into something (like a wall, or an object)

Preventing Marty from walking off a table or other surface

Helping Marty vacuum a room efficiently....

When a bump switch is plugged into Marty’s control board you can detect whether it is being pressed or not using an Input Block in Scratch!

Wondering how to install your bump switches? Here goes...

Every Marty comes with 2 bump switches (one for each foot) so you can attach one to the front of the right foot and one to the front of the left to start with. They are easy to identify as our bump switches have a black, red and white cable and one end will have a metal clip/switch on it. You will learn new positions for them in the 

. They can also be put on the back of the foot so Marty can sense when they bump into something behind them.

Now let's connect the bump switches, one to each foot as follows:

The switch itself can be attached to the foot in various places using two small M2 nuts and bolts. In the pictures below it is shown connected to the front of Marty’s right foot. The screws are 

The photos here show Marty with a bump switch connected. Cable ties can be used to keep the wire out of trouble - 

but make sure to leave enough slack that Marty’s leg can still move properly through the full range of movement!

To connect bump switches to Marty's control board open up Marty’s head by loosening the two screws on either side of Marty’s face until you can open the face and access the electronics inside.

 on it should be fed through the back of Marty's head and plugged into the control board.

The cable for the bump switch can be passed through any of the openings on the back of Marty’s head (on either side of the on/off switch). The cable for the right foot should be fed in on the right side of the on/off switch and the left foot switch should be on the left side of the on/off switch.

The cable can can be twisted before screwing it in to help make it neater. This is how it should look once you've fed the cable through the hole and plugged it in:

(It is often easier to temporarily take off an arm or lift the control board out of the slots to give more working room

In the photo above, the bump switch is connected to GPIO Input 0, so will be readable in Scratch on input 0

It can be plugged into any of 8 “GPIO” ports on Marty’s control board. It is important that it is plugged in with the 

Answer: A GPIO port is a “General Purpose Input/Output” port. It is basically a pin (or port) on a circuit board that does not have a specific function assigned to it. This means it can be used to connect additional sensors or other components, like we are doing here.

Don't forget to screw Marty's back on again when you're finished!

We are going to start by looking at how to check whether the bump switch is being pressed or not.

Create a new Scratch 3 project with the Marty the Robot extension added.

Towards the bottom of Marty’s scratch blocks, you’ll find a block that looks like this:

Double click the block to check the current state of the bump switch. A “1” means the bump switch is pressed, and a “0” means it is unpressed.

One of the simplest ways to use a bump switch in Scratch is to wait until it is pressed before performing an action.

For example, the following block of code will wait until the bump switch is pressed before kicking the right leg. If you want Marty to play football, using a bump switch ensures Marty only kicks a leg when the ball is by the foot.

 section of the code blocks. Inside this block, you will need the block from the 

 section that checks to see if two quantities are 

 to each other. We are going to use it to check to see when the bump switch is pressed - this would be if the output from the bump switch is equal to 1.

 Did Marty kick the ball when you clicked the bump switch that is plugged into GPIO Input 0?

Marty has quite slidey feet, and on a slippery table might slide backwards instead of activating the bump switch. This can usually be overcome by putting some sticky tape on the table to give a grippier surface. Make sure you use tape that won’t mark the table!

Time to think about how Marty could use a bump switch to avoid an obstacle. Program this simple loop to check if the bump switch is pressed at the end of each of Marty's steps. The 

 one step at a time until the bump switch is pressed and its output is 1. 

The problem with this code is that it only checks if the switch is pressed at the end of the step. In reality, it is most likely that it will be pressed halfway through the step!

To sort this we could write some extra code (we can call it block b) to keep track of the bump switch’s value in a variable that we have called 

. This code can be run at the same time as the code telling Marty what to do when the bump switch is pressed. This idea of running two blocks of code at the same time is known as running 

. Have a go at getting the code below running to see how it works:

This way, when Marty gets to the end of each step, we will know if the bump switch was pressed at any point during that step. That is a much more reliable way to keep track of collisions.

It would be even smarter to be able to react the instant a collision happens and the bump switch is pressed, rather than waiting until the end of the step.

This code might look a bit complicated but a good way to start to understand it is to get the code working and see what it does. The first part of the code has stayed the same as before but the second part of the code that runs in parallel has changed and the 

There are a few options for the stop block. “Return to zero” will return Marty to the standing position as directly as possible. You could also finish the current movement, freeze, disable the motors, or pause the current movement (you can resume using the “enable motors” block).

Earlier we mentioned lots of different ways that bump switches are useful - things like solving mazes or robot vacuum cleaners!

Write some code to make Marty turn around when a bump switch is pressed. Here are some things you will need to think about,

How will you know when the bump switch is pressed? 

Look back at the examples that you have already tested in this activity!

Find the right code block in the Marty the Robot code drawer!

What else might Marty do having bumped into something? 

Angry eyebrows? Make a noise? Add effects to make your code more fun!

Here is an example of a possible challenge answer! Start by telling Marty to 

We will know when the bump switch is pressed because the output will be equal to 1. We need a block that will 

When the bump switch is pressed, we can make a scream! That should wake everyone up. Go to the 

 in the top left hand corner then click on 

 in the bottom left corner. Although we chose scream, there are lots of sounds to choose from! Now get a 

 blocks and select the sound you have chosen.

You have now just programmed Marty in Scratch to react when a bump switch is pressed. If you want to continue to explore bump switches, think about:

Where else could you position a bump switch on Marty? 

Try it out and think of examples of when this might be useful!

A Sense of Touch

Using Python, you will create a program that will find all of the Martys connected to your network and control them all using the same commands.

The video above is an example of what you can do whilst controlling more than one robot. In this tutorial we will go over how you can connect and code multiple robots at the same time using a Python script!

A computer with Python 3 and martypy installed (installation guides 

The first thing we need to do is find all of the Martys we can, our army needs as many bodies as possible.

First thing's first, open up IDLE (you will have this application after installing Python) and create a new file by either pressing ctrl+N or going to File->New File

To then allow Python to talk to our Martys we need to write the following at the top of our file. This tells Python to go and get all of the functions that can talk to Marty so that we can then use them.

We can now tell Python to look for any Marty connected to the same WiFi as the computer that we are using. The following line will help us with that.

martypy.SocketClient.discover(timeout=10);

Note that if we just write this and run our program, nothing will happen. This is because we're not doing anything with what the function is telling us, so for now we will save what it returns into a variable called 

unrecruitedMartys = martypy.SocketClient.discover(timeout=10) print(unrecruitedMartys)

In programming, we use variables to remember information for us. This information could be anything from a specific number or the string of text that was just typed into our program by the user. We can then call on the variable when we need the information that it is storing!

You can run your program by selecting Run->Run Module or by pressing F5. When you run your program you should see a list of the available Martys on your network that you can connect to. It should look similar to the following,

[{('192.168.0.57', 4000): b'martyrocks'}, {('192.168.0.58', 4000): b'Anna'}]

Now that we can see the Martys, the next step is to connect to them in order to start controlling them.

We need to use the following command to connect to Marty.

m = martypy.Marty(url='socket://192.168.0.__', client_types=dict(), default_lifelike=True)

 of the Marty we want to connect to. Luckily, we can get that information from the list we printed out earlier after running the 

We can get this information by going through the list of Martys and 

 all of the IP addresses. To do this we will need to use a 

for marty in unrecruitedMartys: print(marty)

In programming, we use loops to repeat a certain action a number of times. For example, if you were going to walk in a square, you would repeat the command 

 four times. Using loops is an easy way to stop duplicating lines of code and makes our programs more readable!

This loop will start with the first Marty in the list and print out that entry before moving through the list and doing the same for each Marty entry in the list.

If we run our program now with this loop included then one of the entries when printed will look like the following,

We can now get a single Marty from our list, but this gives us a lot more information than we actually need. We will only need to extract the IP address from each entry so that we can connect to that Marty. To do this, we need to change our loop slightly,

for marty in unrecruitedMartys: ip = marty.popitem()[0][0]

Lets break this command down a little bit

 command will take a single entry from the list and return it.

 to get the first element in the returned entry which will give us 

 again, we will get the IP address section which is then saved into the variable called 

To get the URL we need to connect to that Marty, we can simply 

. So our command for connecting to a Marty will look like the following,

m = martypy.Marty(url='socket://' + ip, client_types=dict(), default_lifelike=True)

Finally we can connect to our Martys. As we may not know how many Martys we will be controlling we're going to need a list that holds all of the connections. Let's create an empty list just above the loop we created to gather the IP addresses,

We can then put it all together and connect to all of the Martys that are on the same WiFi as our device,

import martypy
unrecruitedMartys = martypy.SocketClient.discover(timeout=10); 
martys = [] 
for marty in unrecruitedMartys: 
   print("getting") 
   ip = marty.popitem() 
   print(ip) ip = ip[0][0] 
   print(ip) m = martypy.Marty(url='socket://'+ ip, client_types=dict(), default_lifelike=True) 
   martys.append(m)

We now have a list of connections to our Marty army, lets actually use them!

To control our Martys, we will need to run through the list of Martys that we have connected to and call 

 block in Scratch - it tells Marty to reset all of the motors and get ready to move!

Add in another loop to your program and add a few moves for your Marty army to complete. You might want to look at the martypy documentation 

Here is some example code to help you out with controlling your Marty army,

You now have control of your very own Marty army that you can code and control. If you want to continue to explore using martypy to code multiple robots at the same time, here are some ideas!

Pick a song and code your very own robot flash mob dance routine

Cast and code your own play featuring your Martys. 

You will need to think about controlling the different robots to do different things!

An Army Of Martys

Using Scratch 3, you will create an interactive game where you need to help Marty catch their favourite snacks that are falling from the sky to earn points. There are also some snacks falling from the sky that Marty doesn't like so we need to avoid them!

After completing this activity, you could then add your own twists to the game to make it harder or more challenging for players.

Using sensing blocks to work out what characters on the stage are touching

Coding variables to keep track of a score

Logical if statements to help us make decisions during the game

This activity introduces some key concepts of programming that can also be found in our 

Before we start coding our game, we need to make sure that we set the scene with a Marty sprite on the stage.

Click the button below to open a brand new Scratch project, ready for coding.

You will notice that on the stage, there is currently a cat. We want our main character to be Marty and not Scratch cat so we need to remove them from the stage. To do this, click on the delete button as shown below,

Next, we want to add a new character (or 

 as it is called in Scratch). But we don't want to use one of the options that Scratch have already built in. We want to upload our own character image to be used. Download and save the image using the button below,

Great! Now we are ready to upload our image of Marty into our Scratch project as the main character.

To do this, we need to hover over the cat face icon and select the option to 

 as shown below. Then all that is left to do is select the Marty image wherever it is stored in your files.

You might notice that the Marty on the Scratch stage is a little big. Let's change that!

All you have to do is change the number in the 

 textbox. Try playing around with this number until you find a size that you think is sensible. We set ours to 30.

Hopefully you now have something that looks like this...

If we want Marty to be able to move side to side to catch the falling food, then we will need to code some movements.

When we click the left arrow key on our keyboard we want Marty to move left and when we click on the right arrow key on our keyboard we want Marty to move right.

Let's start with clicking on the right arrow key,

When you click on the right arrow key, Marty should now move along the screen to the right. We just need to add in some instructions to move left. But this time because we want to move in the opposite direction we will need to use the '

 sign so our character knows to move the other way.

: You can think of these numbers like a number line. As you go along the number line towards the positive numbers you go to the right and if you go towards the negative numbers you move along the left!

Challenge: coding marty to move faster or slower

We now have Marty moving from side to side, ready to catch some food. But how could we change our code to make Marty move faster or slower?

All we need to do to change the speed that Marty moves across our screen is change the number in our blue 

Try changing the number 10 to a bigger number. What happens? Hopefully, you will notice that Marty moves across the screen in bigger 

Now try and change that number to something less than 10. Marty is now taking smaller steps so is moving slower than before.

Play around with this number and decide what speed you want Marty to move!

Our game is starting to take shape, the next step is to add in some snacks for Marty to try and catch!

The first snack we are going to add into our game is something that Marty likes. For this, we are going to add in some bananas for Marty to catch but you can pick what you think Marty's favourite snack would be!

To add in our bananas, we just need to add in a new sprite using the 

Don't forget to re-size the new sprite that you add in! You should have something like below,

The bananas are going to randomly drop from different parts of the sky on our stage. To do this we need to think about 

 and where the bananas will be on the screen. Take a look at this block,

This block will tell a sprite to go to different parts of the stage based on the coordinates that we give it. The very middle of the stage will have the coordinates 0 for 

Try moving your sprite around on the stage and see how their 

After exploring how these coordinates work, we know roughly where the top of the stage is but how do we make sure the snack isn't dropped from the middle of the screen all the time?

 block will pick a random number between the numbers that we tell it. In here, we have included the most left position and most right position that we could drop the snack from. That means that the snack will randomly fall from different parts of the top of the screen.

You can use these numbers in your program too!

Lets put that together with a few other instruction blocks,

We want to hide the snack so that the player can't see where it goes until it is ready to start falling from the sky. We have also added in a short pause so that the snack doesn't always fall at the same time.

We have Marty's favourite snack appearing at random parts along the top of the screen so now we need to add in some coding blocks to see some food falling from the sky.

To code the food to start falling down the screen, we need to slowly decrease the 

 of the sprite. Using a loop, we want to keep doing this until the snack is either caught by Marty or reaches the bottom of the screen,

What happens if you change the number in the 

By putting together all of those instructions we get something that looks like,

loop so that the food will keep falling throughout the game and not just once!

What happens when marty catches the snack?

You might notice when you tested your game that when Marty catches the bananas, they disappear and go back to the top of the screen but it would be nice if there was some kind of noise that let us know we caught them!!

Before we play the sound, we need to double check that Marty has in fact caught the snack falling down the screen. We can use an if statement again to help us do this and if the two sprites are touching then we can play a fun sound to let the player know they have successfully caught that falling snack!

Here's what the instructions for our banana sprite look like now,

Make sure the new instructions to play a sound are inside of the forever loop

We now have one falling snack for Marty to catch but wouldn't it be fun to have another one? This time, lets add in a snack that Marty doesn't like so needs to try and avoid!

The first step is to add a new sprite to the stage like we did for the bananas. This time you need to pick something that Marty does not like. We decided to add a donut as the snack that Marty does not like!

Then the code for this new snack will be exactly that same as the code we put together for the bananas. Here's a reminder of what that looked like,

challenge: can you add in your own sound recording?

It would be pretty cool if we could change the sound that was played when we catch the food Marty doesn't like to be an annoying noise to let the player know they caught the wrong snack!

It is really easy to add in our own sounds to a Scratch project. You can even record your own voice and play it back in your game!

To do this, all you need to do is click on the arrow beside the sound block that we have in our program and click on the option to 

We now have an awesome game that lets the player help Marty catch their favourite snack and avoid the others falling from the sky! The final step is to keep a score.

To keep track of our score, we will need to use something called a 

. A variable is used in programming to remember something for us, in our case, we ill use it to store and remember the score in our game. Let's start off by creating a brand new variable called 

We then need to set the score to start off at 0. Let's add this code into the code blocks that we have for Marty,

Building a Game in Scratch

Control your Marty with a GamePad using Python

The Logitech F710 GamepadJust as a side-note, if you're running Marty with a Raspberry Pi and ROS installed, then there's a ROS-based Joystick controller for Marty 

 here, but most USB gamepads should work. Drivers and supported features might be different between different controllers, and some bluetooth controllers might work too. Something that looks like a 'normal' console controller with plenty of buttons, joysticks and triggers is ideal!

 running with our current hardware (i.e. a 

) - Though if you're running the way-old I2C Servo Board + Raspberry Pi combination, it is possible to adapt this example to work there too.

Lastly, you need to have a working Python install (

 Python 3) on your Computer/Raspberry Pi. If you've never used Python before then we'd recommend first running through a basic Python tutorial to get you well acquainted with Python.

The first thing we'll need to do is create a project folder to work in, something like 

. Now we should install a few things in the folder; the commands below are for doing this in a 

We'll create an environment for our project to run in, called a 

 for short. This lets us choose exactly what version of Python and which libraries we want to use, separately from the ones that already come installed on your system.

 that contain some Python code we can use to help us work with the Game controller and Marty.

, we then need to install the latest version of 

, Robotical's Python library for Marty, and 

, an aptly named library for using Input Devices like Gamepads, Mice and Keyboards:

(VENV) $ pip install martypy 
(VENV) $ pip install inputs

 If you use IDLE, Python's built-in IDE, you can start it 

 your venv like so, again from the command line:

Next Step - Getting the controller working

Our first task is going to be getting python to respond and do stuff when we press buttons and move controls on the Gamepad. We'll make a Python file, called 

 in the Project folder we made earlier. Open it in a code editor like IDLE or 

 library we just installed, then, we'll ask it to tell us what 

, which will print something that looks like this to the terminal:

(VENV) $ python ./joystick.py 
[inputs.GamePad("/dev/input/by-id/usb-Logitech_Wireless_Gamepad_F710_4C089F2D-event-joystick")]

Learning Portal

A Sense of Touch

An Army Of Martys

Building a Game in Scratch

Control Your Marty With A Gamepad Using Python

Dance Like Drake!

Distance Sensor Introduction

Drummer Marty!

Easter Bingo

Egg and Spoon Race