Software Setup

Use the Raspberry Pi Imager utility to program the Raspberry Pi OS image to the microSD card as shown below.
1. Insert the microSD card in the microSD card reader and plug the microSD card reader into the computer
2. Open the Raspberry Pi Imager from the Applications directory on the Flash drive
3. Select the “CHOOSE OS” button
4. Select the “Raspberry Pi OS (other)” option from the list
5. Select the “Raspberry Pi OS Lite (32-bit)” option from the list
6. Select the “CHOOSE STORAGE” button
7. Select the microSD card
  
  The size of the microSD card should be approximately 16GB
  
  If the microSD card already has an image on it then it will show Mounted as /Volumes/boot
8. Hold down the Shift + Control + X keys at the same time to open the Advanced options window
9. Click the box next to the “Set hostname:” option and change the value to “pibot##” where the ## comes from the label on the PiBot
10. Click the box next to the “Enable SSH” option and set the password for the pi user to “DogsAndCatsAreNice2.”
11. Scroll down, click the box next to the “Configure wifi” option and type the SSID, password, and select the Wifi country for your Wifi network
  
  The SSID and password for will be filled in by default based on the network your computer is connected to
  
  Click the box next to the “Show password” option to see the Wifi password
  
  If your wireless network doesn't have a password, skip this step and follow the instructions here after finishing the steps below to write the SD Card
  
  If you are outside the United States then use the Wifi country code with the appropriate ISO 3166 alpha-2 country code
12. Scroll down, click the box next to the “Set locale settings” option and select the Timezone and Keyboard settings for your location
  
  The Timezone and Keyboard will be filled in by default based on your computer settings
  
  If you are outside the United States then use the Timezone with the appropriate TZ Database Time Zone
13. Click the Save button to close the Advanced options window and return to the main window
14. Select the “WRITE” button
15. Click the “YES” button when asked if you want to continue
  
  If asked for your password to continue, enter it to give permission to write to the microSD card
16. When the Raspberry Pi Imager utility has finished, click the “CONTINUE” button and close the Raspberry Pi Imager utility
17. Remove the microSD card reader from the computer
Remove the microSD card from the microSD card reader and plug it into the Raspberry Pi board as shown below
Install charged 18650 batteries in the 18650 battery box and slide the switch to the “ON” position
Wait 3-5 minutes for the green light to stop flashing
Open the terminal app

Click the magnifying glass in the top right corner of the screen and type “terminal” to find the terminal app
Type the following command and press enter to clear out any previous SSH host keys

Replace the text “pibot##” with the label on the PiBot
```
ssh-keygen -R pibot##.local
```
Type the following command and press enter to import the new SSH host keys

Replace the text “pibot##” with the label on the PiBot
```
ssh-keyscan pibot##.local >> ~/.ssh/known_hosts
```
Type the following command and press enter to connect to the Raspberry Pi terminal via SSH

Replace the text “pibot##” with the label on the PiBot

The password to enter when prompted is “DogsAndCatsAreNice2.” without the quotes. The '.' at the end is important!
```
ssh pi@pibot##.local
```
Perform the following steps to enable the I2C interface on the Raspberry Pi board
1. Type the following command and press enter to run the Raspberry Pi configuration utility
```
sudo raspi-config
```
2. Use the up and down arrow keys to select the “Interfacing Options” menu item and then press the enter key
3. Use the up and down arrow keys to select the “I2C” menu item and press the enter key
4. Use the left and right arrow keys to select the “Yes” option and press the enter key
5. Select the “Ok” option and press the enter key
6. Use the left and right arrow keys to select the “Finish” option and press the enter key
Type the following commands and press enter after each line to install the rpi.GPIO library and the PIP3 application

Answer “yes” or “y” when asked to install extra packages or continue
```
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install python3-rpi.gpio python3-pip
```
Type the following command and press enter to install the Adafruit-pca9685 library
```
sudo pip3 install adafruit-pca9685
```
Type the following commands and press enter after each line to create a directory for the PiBot code
```
mkdir -p ~/pibot
cd ~/pibot
```
Type the following command and press enter to download the Python code for this lesson
```
wget http://osoyoo.com/driver/picar/picar-basic.py
```
Place the PiBot on the floor in an area that is free of any obstacles
Type the following command and press enter to make the PiBot move
```
python3 picar-basic.py
```
Type the following command and press enter to close the SSH connection
```
exit
```

Software Explanation

To view the code that makes the PiBot run perform the following steps
1. Open the Visual Studio Code from the Applications directory on the flash drive
2. Click on the small green square in the bottom left corner of the screen
3. Select the “Remote-SSH: Connect Current Window to Host…” option
4. Type “pi@pibot##.local” and press enter
  
  Replace the text “pibot##” with the label on the PiBot
  
  The password to enter when prompted is “DogsAndCatsAreNice2.” without the quotes. The '.' at the end is important!
  
  It may take a couple of minutes while it installs some files on the PiBot
5. Click the icon that looks like two pieces of paper in the upper left of the window and click the “Open Folder” button
6. Select the “pibot” folder and click the “OK” button
7. Select the picar-basic.py file in the list on the left
Find line 20 in the picar-basic.py file. What is the name of the variable? What value is assigned to the variable? What do you think this value controls on the PiBot?

The line numbers are displayed to the left of each line of text and are a feature of the Visual Studio Code editor

Variables are short “words” that can hold values. They allow you to change the value in one place and have it updated in multiple places in the code. They also allow the code to change the value of the variable.

Values are assigned to variables using the '=' character
Find the other places in the code where this variable is used. How many of them are there?

When you see some text followed by a '(' with some more text and then a ')' that is a function call. The text before the '(' is the function name. The text between the '(' and ')' are parameters that get passed to the function. What the function does is defined by a 'def' in front of the function name somewhere in the code.

Functions allow a common set of steps to be used in many places in the code without having to type in all of those steps each time.
Find the definition of the function that uses the variable. What does the function do?

In the definition of the function, the text between the '(' and ')' may be different from when it is called. When the function is called, the variable that is passed to it replaces the name from the definition.

See the Electrical Description section on the previous page for a description of what the pwm does
How would you change the code to make the PiBot move faster? How about to make it move slower? Make one of those changes to the code and save it using File→Save.
Open a terminal in Visual Studio Code from the Terminal→New Terminal menu
Type the following command and press enter to make the PiBot move with your changes
```
python3 picar-basic.py
```
Try out the other change to the code following the same steps
When you're finished testing out your changes type the following command in the terminal and press enter to shutdown the PiBot
```
sudo shutdown -h now
```
Click on the small green rectangle in the bottom left corner of the screen and select “Close Remote Connection”
Wait 3-5 minutes for the green light on the Raspberry Pi to stop flashing and turn off the switch on the PiBot battery

"For everything created by God is good, and nothing is to be rejected if it is received with thanksgiving, for it is made holy by the word of God and prayer. - 1 Timothy 4:4-5"