Expectations

Learning Targets

• I can connect to my Raspberry Pi via SSH.

• I can deploy an app to a Raspberry Pi.

Assessments

• You will submit a link to your GitHub repo.

• You will demonstrate your capacity to control your robot.

• You will be asked regular comprehension questions about Raspberry Pis.

Open House Demo

During our school's open house days, I setup a few GoPiGo robots that respond when visitors hold their hand in front of the sensors. We'll make our own version of this function. It's fun and an easy way for us to start responding to data from the ultrasonic sensor.

Work the us_sensor

1. Power-up your robot and connect over SSH

2. Go to your project folder: cd PnR-Final

3. Launch Python: python

4. Import our file: import student

5. Instantiate our Piggy: p = student.Piggy()

6. Experiment with the sensor with p.dist()

Setup the method

Let's look at our menu and create a new option for open house. We'll keep checking dist() and perform some sort of action when it returns a number too close

Nav Skills

Before you start on your project to experiment with and grow your own navigational algorithm, let's go over a few helpful tricks.

Counting Obstacles

Let's imagine a list of about twenty distance measurements: [200, 210, 204, 3, 2, 7, 197, 221, 211, 1, 5, 5, 3, 205, 202]

How many obstacles do you think were found in this set of distance measurements?

Our GoPiGo's keep a list of 180 measurements, self.scan, that corresponds to the servo's angle when taking measurements. Here's the starting code to count obstacles directly in front of the robot:

    def obstacle_count(self):
        """scans and estimates the number of obstacles within sight"""
        self.wide_scan()
        found_something = False
        counter = 0
        for ang, distance in enumerate(self.scan):
            if distance and distance < 200 and not found_something:
                found_something = True
                counter += 1
                print("Object # %d found, I think" % counter)
            if distance and distance > 200 and found_something:
                found_something = False
        print("\n----I SEE %d OBJECTS----\n" % counter)

Let's try this out and see if it's accurate. Can you improve its accuracy?

Next, let's try to modify the method to get a 360 degree view of all the obstacles around our robot.

Left or Right?

We've already experimented with self.wide_scan(). We use that method to fill the self.scan list with data. For example, self.scan[60] is the distance found at the servo's 60 degree angle.

What's the distance at the midpoint of your robot?

# create two variables, left_total and right_total
# loop from self.MIDPOINT - 60 to self.MIDPOINT
    # add up the numbers to right_total
# loop from self.MIDPOINT to self.MIDPOINT + 60
    # add up the numbers to left_total
# if right is bigger:
    # turn right
# if left is bigger: 
    # turn left

Turn Until Clear

We've also used the self.is_clear() option to tell whether or not the space right in front of the robot is clear. Create a loop that keeps turning the robot until it's clear.

Nav Algorithm

Expectations

Learning Targets

• I can connect to my Raspberry Pi via SSH.

• I can deploy an app to a Raspberry Pi.

Assessments

• You will submit a link to your GitHub repo.

• You will demonstrate your capacity to control your robot.

• You will be asked regular comprehension questions about Raspberry Pis.

Terms

Printed Circuit Board (PCB)

Single Board Computer (SBC)

This is a PCB with all the basic components found in a personal computer (PC)

Microcontroller Unit (MCU)

Linux

Setup your robot

I'll help you remote control (SSH) your robot.

Check and Update

• Learn more about updating Raspberry Pi

• Learn more about the Command Line Interface

sudo apt-get update

sudo apt-get upgrade

Ready to shut down? sudo shutdown now

Local Python Practice

Now that we've left the fun environment of Trinket.io, let's first build a practice project.

Now let's go to VS Code and clone your forked repo.

The URL we need is: https://github.com/YOUR-USERNAME/TurtleChase

Now let's add some new features together:

1. Add a button to change each player's color

2. Prevent players from traveling off the screen

3. Detect collision of players

4. Wire up some other SuperTurtle methods...?

Now let's commit and push our code.

Expectations

We're going to take a tour of Python. You are expected to know generally what these things are, you're not yet expected to know how to use them. So no freaking out. We'll play around with some fun projects after a quick look around.

Learning Targets

• I can make a hello world app in Python.

• I can differentiate between compile-time, run-time, and logic errors.

• I can describe the basic constructs of programming languages such as variables, conditionals, loops, and flow control.

Assessments

• You will be answering comprehension questions about the layers supporting software execution.

• You will be creating and submitting your first Python app using trinket.io

Let's go to trinket.io and build some simple stuff, starting with print("Hello, world")

We'll go over each of these concepts in greater detail. For now, let's skim over all the big topics.

Data Types

The first thing we'll tinker with is declaring variables and storing information. Variables in Python are dynamically typed, meaning you can store one type of information in a variable and then switch it without any fuss. Other languages are more strict and don't allow such shenanigans.

Operations

We use math symbols for most common operations. But Python has some cool operators. Read!

Conditionals

Now we're switching from declarations and operations to control flow. Now we can direct the computer's train of thought (aka its thread).

Loops

This is how we repeat commands and iterate through a list or collection of items. Imagine you're using your hand to flip through posters at Walmart. Your hand selects each poster as it traverses the collection. That makes your hand the iterator as it is connecting with each object in the collection during the loop.

Functions/Methods

A function is a set of commands you can call. When activating this "magic spell" you can pass it parameters or ingredients.

Classes

A class is how you can create your own objects. You can make an class serve as a single worker like a static library of mathematical operations or you can design your own object, like a Spaceship that can be spawned or instantiated into a game many times. It'll have its own instance variables like health and shield properties.

Expectations

Learning Targets

• I can compose a higher-ordered algorithm.

• I can update code on my Raspberry Pi.

• I can make short, descriptive commit messages.

Assessments

• Your GitHub repo will be regularly reviewed.

• You will demonstrate your capacity to control your robot.

• You will be asked regular comprehension questions about Python and deployment.

Coding the project

Fork code

3. Use the git: clone command and paste your GitHub url. You should now see your code on your editor. Explore student.py and teacher.py.

5. Remove the Piggy folder if it's already there: rm -rf Piggy

6. Now we'll clone your project on the robot too with git clone https://github.com/YOURUSERNAME/Piggy

7. Change to your project folder: cd Piggy

8. Run the app: python3 student.py

Push code to GitHub

You you make changes to your app and want to update the code on your robot, we first need to send the code from our computers to GitHub.

Pull code on robot

Now we'll remote control our robots using SSH. We'll use Linux commands to pull the updated code down from GitHub.

1. Make sure you're in the right folder: cd Piggy

2. Pull your updated code: git pull origin master

3. Run your app: python3 student.py

4. If it doesn't run, study the error.

Calibrate

We'll need to configure your class variables.

Midpoint

Motor Speeds

Sometimes one motor will perform faster than the other, giving the robot a noticeable veer. We can try to correct for this drift by adjusting the motor power.

Dance Project

Check out what commands are available from the API that's provided for you. These are the commands you're inheriting.

Higher-Ordered Logic

Your dance method should read as close to regular English as possible. The nitty-gritty commands are all kept in the particular methods being called in your dance algorithm. So your dance method should just call a handful of moves. Within those moves, you'll use the specific motor commands below and get into the nitty-gritty of robot control.

• deg_fwd(angle) - how many degrees do you want your wheels to rotate? You need to pass the angle

• turn_to_deg(angle) - rotates to the given angle as calculated by the piggy's gyroscope

• turn_by_deg(angle) - turns relative to it's current heading. Positive values rotate right and negative rotate left

• fwd - powers on your robot to drive forward. You'll need to use self.stop() to power off the motors

• right - by default, self.right() will give the left motor 90% power and the right 0% which rotates right. You can use kwargs to adjust the power such as self.right(primary=90, counter=-90), which will spin the robot in place

• left - same as right but reversed.

• back - same as fwd but in reverse.

• servo - moves the servo (plugged into servo1) to the given value (use 1000 - 2000)

• stop - sets motor power to zero

• read_distance - returns the distance from the distance sensor (plugged into I2C port) in millimeters

• get_heading - returns the gyroscope's value