Raspberry Pi

What is Raspberry Pi and How to use a pi for beginner.

What is a Raspberry Pi?

What is Raspberry Pi?

Raspberry Pi is a series of small single-board computers. The Raspberry Pi project originally leaned towards the promotion of teaching basic computer science in schools and developing countries. It is widely used in many areas because of its low cost, modularity, and open design.

The Raspberry Pi Foundation provides Raspberry Pi OS, a Debian-based Linux distribution for download. It promotes Python and Scratch as the main programming languages, with support for many other languages.

Things you need to know about your Pi

Raspberry Pi comes with a lot of different models and each of them has its own specs. To get started, you first need to know the model of your Pi and look at the specs.

Things you need to set up your Pi

Raspberry Pi is a single-board computer. You can image it as the core of your computer but has no monitor, keyboard or mouse. It can run automated functions without all those things, but you still need them when you are setting up. All necessary parts are included in the CTH Raspberry Pi's kit.

1. Screen

You can use any screen, as long as it has a HDMI port and you have a power supply for the screen.

2. HDMI cable

Different models have different types of HDMI ports, you will need to find HDMI cable that matches your Pi.

  1. Pi 3: standard HDMI port x1
  2. Pi 4 & Pi 5: micro HDMI port x2
3. Mouse and with cable

You can also use the Bluetooth with a dongle type of mouse & keyboard.

4. Power Supply

Different models have different needs for Power supply. It is not necessary to buy the official power supply. However, you will need to find one that matches the needs of your pi, please refer to the official document.

  1. Raspberry Pi Zero 2 / Pi 3: 5V, 2.5A; Micro USB
  2. Raspberry Pi 4: 5V, 3A; USB-C
  3. Raspberry Pi 5: 5.1V, 5A; USB-C
5. SD card

The SD card acts as the hard drive of your Raspberry Pi. The higher storage means your pi can save more things on it. BUT, you have to be aware of the types and sizes of the SD card. There is a list for you to check the specific SD card's compatibility with Pi.

In general, I will suggest using one with at least 16GB.

6. Good to have

  1. Ethernet Cable - In case you cannot log in to the WIFI, especially for non-open networks.

  2. Fans - Overheating is a common problem for Pi, especially when running for hours.

  3. Cameras - With cameras, you can do a lot of interesting projects with computer vision and images.

What is a Raspberry Pi Pico?

What is Raspberry Pi Pico?

The Raspberry Pi Pico is a microcontroller board developed by the Raspberry Pi Foundation. It was announced in January 2021 and represents a departure from the traditional single-board computers (SBCs) that the Raspberry Pi Foundation is known for, such as the Raspberry Pi 3 or 4. Instead of being a full-fledged computer, the Raspberry Pi Pico is a microcontroller board designed for embedded projects and electronics prototyping. It is closer to an Arduino than a Raspberry Pi.

The Pico includes 26 programmable general-purpose input/output (GPIO) pins, which can be used for various digital and analogue tasks. The Pico can be programmed using MicroPython, a lightweight version of the Python programming language designed for microcontrollers. It also supports C and other programming languages. To know more about Pico.

At the moment, The Raspberry Pi Pico family currently consists of four boards; Raspberry Pi Pico, Pico H , Pico W, and Pico WH. Raspberry Pi Pico W and Pico WH have on-board single-band 2.4GHz wireless interfaces.

Set up your Pico

  1. Solder header pins onto the Pico, you can choose the types that you prefer.
  2. Choose a programming language for your Pico, in this tutorial, we will be using MicroPython.
  3. Download the correct MicroPython .uf2 file for your board. Raspberry Pi Pico or Raspberry Pi Pico W
  4. Push and hold the BOOTSEL button.
  5. Plug your Pico into your computer with a USB cable.
  6. It will show up as an external drive called RPI-RP2.
  7. Copy the MicroPython .uf2 file onto the RPI-RP2.
  8. Pico will reboot, then you are ready to go!

Download Thonny

Thonny is an integrated development environment (IDE) for Python programming. It is designed with beginners in mind and provides a simple and clean interface for writing and running Python code. Thonny includes features such as an interactive Python shell, a built-in package manager, and the ability to easily install and manage Python packages. Download here.

thonny.png

Get Started

This example code will blink the built-in LED every 0.5 seconds, using the machine library and the time module.

  1. Put in your code
from time import sleep
from machine import Pin
led = Pin("LED", Pin.OUT)        #create LED object from pin13,Set Pin13 to output

while True:
  led.value(1)            #Set led turn on
  time.sleep(0.5)         #stay on for 0.5 seconds
  led.value(0)            #Set led turn off
  time.sleep(0.5)         #stay off for 0.5 seconds

  1. Choose the board and port at the right bottom corner. thonny-2.png

  2. You can hit the green play button now, it will be blinking!

  3. After testing the code and you are happy about it, save the code as main.py on Raspberry Pi Pico.

  4. Pico will run any code named main.py automatically whenever it is powered. But remember to save a file with an identifiable file name on your computer, otherwise you will end up with a bunch of main.py without knowing what they do.

  5. At this point, you don't need your computer anymore. You can power the Pico with a phone charger or battery.

What are GPIO pins on Raspberry Pi?

What is GPIO?

GPIO stands for General-Purpose Input/Output. GPIOs have no predefined purpose and are unused by default. If used, the purpose and behaviour of a GPIO are defined and implemented by the user. You can find the GPIO pins on the top of most Raspberry Pi models or other microcontrollers such as Arduino.

GPIO pins are mostly used for connecting electronics with computers/microcontrollers. These components can then be programmed to perform different tasks using different languages, such as C++, Python and Scratch. In this tutorials, we will focus on the GPIO pins on Raspberry Pi.

Numbering of GPIO pins

GPIO pins on Raspberry Pi have two numbering systems, Board and Boardcom (BCM). For example, the board pin 8 and BCM pin 14 are referring the same pin. Numbering is important based on which programming languages and libraries you use.

1. BCM numbering

BCM numbering matches up with the tiny labels printed on the Raspberry Pi, like GPIO14. It is used in most programming languages such as Python and Scratch.

2. Board numbering

Board numbering is based on the physical locations of the pins on the Raspberry Pi. It starts from the top left corner as Pin 1, left to right then next line, and the bottom right will be the last pin, Pin 40. Board numbering is less common to be used, the only place you will see is probably in one or two Python libraries.

3. Functionalities of the Pins

Each pin on the pi has different functions and their physical locations may move from model to model. The pins without a BCM number are power output pins, such as GND and 5VDC. Pins with a BCM number are all PWM pins which can be used as input or output. Besides being a PWM pin, they also have other unique functions, such as GPIO 02 and GPIO 03 are also the pins of SDA and SCL for I²C communication. You can refer to the pinout of each model to find out more details of each pin.

Building Circuit with Raspberry Pi

UNPLUG your Pi when you are connecting electronics and DOUBLE CHECK your connections!Raspberry Pi is not short-circuit-proof as Arduino. If you have a short circuit or you give more power than it could take to the GPIO pins, it will break the Pi.

You will probably need a breadboard to make connections easier. In general, I will not suggest direct soldering on a Raspberry Pi, so it can be reused more easily. You can also use a jumper cable to extend all pins to a breadboard.

There are many options to program a Raspberry Pi with physical computing components, including Scratch, Bash, Node.js, C etc. We will focus on Python here. Below are two codes using two different libraries but doing the exact same thing.

1. gpiozero

The main thing to remember about gpiozero library is that it focuses on buttons and LED instead of the actual GPIO pins. i.e. LED = OUTPUT, button = INPUT. Some people may find the syntax easier to understand, like turning on the LED is literally leds.on(). gpiozero is simple and quick and it's a great place to start experimenting as a beginner. But if you are not actually using LEDs or buttons, it can be a bit confusing and it is not very compatible to merge with codes from other libraries as well. Find its documentation here.

# example of programming Raspberry Pi GPIO with gpiozero
# refer to gpiozero.readthedocs.io

import gpiozero as gpzero
from time import sleep

# set up pushbutton and bank of leds
resetbutton = gpzero.Button(3)
leds = gpzero.LEDBoard(26,16,20,21)

# functions to control behavior
def LightsOn ():
    while resetbutton.is_pressed:
        leds.on()
    
def ResetCounter ():
    global counter
    leds.off()
    counter = 0
    
def binary2lights(showThis):
    leds.value = (
        showThis & 0b1000,
        showThis & 0b0100,
        showThis & 0b0010,
        showThis & 0b0001)
    
# setup button handlers    
resetbutton.when_pressed = LightsOn
resetbutton.when_released = ResetCounter

# send 0...15 to lights
while True:
    ResetCounter()
    while counter < 16:
        binary2lights(counter)
        counter += 1
        sleep(1)
2. RPi.GPIO

Borken Library!This library is currently not usable for Raspberry Pi 5. If you are using Pi 4 or older, it will be fine.

RPi.GPIO is a code library that allows Python to communicate with the GPIO. It is widely used and supported. In fact, gpiozero is developed based on RPi.GPIO. I find this library closer to C++ in Arduino IDE. For example, instead of on() and off(), it uses HIGH and LOW. Find its documentation here.

# example of programming Raspberry Pi GPIO with rpi.gpio
# refer to sourceforge.net/p/raspberry-gpio-python/wiki/Home

import RPi.GPIO as GPIO
from time import sleep

GPIO.setmode(GPIO.BCM) # declare BCM numbering scheme (vs GPIO.BOARD)

# set up pushbutton and bank of leds
resetbutton = 3
leds = [26, 16, 20, 21]
GPIO.setup(3, GPIO.IN)
GPIO.setup(leds, GPIO.OUT)

# function to handle reset button
def handleReset ():
    while not GPIO.input(resetbutton):
        GPIO.output(leds, GPIO.HIGH)
        print("waiting for button")
    resetLightsandCounter()


def resetLightsandCounter():
    global counter
    GPIO.output(leds, GPIO.LOW)
    counter = 0
    print("reset")
    
    
# setup button handlers
GPIO.add_event_detect(resetbutton, GPIO.FALLING)

# send 0...15 to lights
while True:
    resetLightsandCounter()
    while counter < 16:
        if GPIO.event_detected(resetbutton):
            handleReset()
        GPIO.output(leds, (
            GPIO.HIGH if counter & 0b1000 else GPIO.LOW,
            GPIO.HIGH if counter & 0b0100 else GPIO.LOW,
            GPIO.HIGH if counter & 0b0010 else GPIO.LOW,
            GPIO.HIGH if counter & 0b0001 else GPIO.LOW
        )
    )
        counter += 1
        sleep(1)

Raspberry Pi Image

Raspberry Pi Image

How to image a Raspberry Pi

How to image a Raspberry Pi?

There is an official video showing how if you prefer.

1. Download the Raspberry Pi Imager

Go to the Raspbeery Pi official site to download the software. Choose a suitable version for yourself.

installImager.png

2. Insert your SD card

A CTL Pi kit should contain an SD card. Insert the SD card into your computer. It is always a good habit to format the SD card before imaging it. You need the SD card to be in FAT32 format.

Open Raspberry Pi Imager v1.8.4, you can format the SD card directly.

  1. Storage, select the SD card
  2. Operating System - Erase

format.png

  1. Click Next and wait for it to finish.

3. Image your Pi

Using Raspberry Pi Imager software to Install the Raspberry Pi OS to the SD card.

imager.png

  1. Raspberry Pi Device, select Raspberry Pi Model

imager-model.png

  1. Operation System, select Raspberry Pi OS, if you are not sure which to choose, choose the recommended one.

imager-os.png

  1. Storage, select the SD card

imager-storage.png

  1. Click Next, then you will be prompted with "Would you like to apply OS customisation settings?", and choose NO.

image-3.png

Once the pi is imaged, it is a ready to go mini computer. Eject the SD card from your computer, plug it into the Pi, power the Pi, it's done!

Raspberry Pi Image

Raspberry Pi Image: Retropie for Reviving Vintage Games

What is Retropie?

retropie.png

RetroPie allows you to turn your Raspberry Pi into a retro-gaming machine. It builds upon Raspbian, EmulationStation, RetroArch and many other projects to enable you to play your favourite Arcade, home console, and classic PC games with the minimum set-up. Learn more.

RetroPie sits on top of a full OS, you can install it on an existing Raspbian, or start with the RetroPie image and add additional software later. It's up to you.

We are using Raspberry Pi Imager. We have a more detailed tutorial for imaging the Pi.

1. Using Raspberry Pi Imager

  1. Raspberry Pi Device select Raspberry Pi Model
  2. Storage select the SD card

imager.png

  1. Operation System - select Emulation and game OS - select RetroPie - select your Pi model retropie1.png

Your Pi is now an emulator ready to go!

2. Controller Configuration

RetroPie can support a range of controllers and even arcade buttons and joysticks. PS5 controller is not supported at the moment(02/2024). You will see the Welcome page, plug in your controller with a USB cable and hold any button on your device.

Press the buttons on your controller accordingly, one by one.

If you want to skip any button configuration, just hold any button.

There are some buttons that you MUST set up, including Hotkey, Start, Select, A and B.

3. Finding Roms

ROM is Read Only Memory, which can be seen as games that can be run on emulators. Thanks to the generosity of some of the original creators of the classic games that MAME® can emulate, several games have been released for free, non-commercial use on MAMEdev. The copyright laws around the use of ROMs are mostly between illegal and grey areas, so no suggestion on where to download ROMs will be provided in this tutorial and no one on our team will answer you in person either.

Different emulators require different file extension so the ROMs can be read properly, such as GBA needs .7z, .gba or .zip. Please see more ROM file formats here.

4. Transferring Roms

Transferring via a USB stick is the most straightforward method. You can find other ways of transferring in RetroPie Docs.

  1. Format the USB stick as FAT32. (You can refer to #2 of this tutorial.)
  2. Create a folder called retropie on the USB stick.
  3. Plug the USB stick into the Pi and wait for 5-10 minutes.
  4. Remove the USB stick and plug it into your computer.
  5. You should see retropie/roms/, the Pi has created all the necessary folders for you in the USB stick. retropieFolder.png
  6. Copy the ROMs to the according folder. For example, you can copy the MAME ROMs in retropie/roms/mame-libretro
  7. Plug the USB stick back into the Pi, and wait for 5-10 minutes again.
  8. Refresh the game listing in EmulationStation by pressing press Start on your controller - Quit-Restart Emulation Station
  9. Now you should your game showing on the Pi and you can start playing your game!
  10. If not, please go back to step 7 and do it again.

5. Want more?

RetroPie can be customized to a high extent, including controllers, UI, cheats, shaders etc.

For more detailed documentation, please visit RetroPie Docs.

Raspberry Pi Image

Raspberry Pi Image: Video Looper

What is Raspberry Pi Video Looper?

Raspberry Pi Video Looper is a simple way to display seamless looping video files, for example in an art exhibition. All you need is a Raspberry Pi, an SD card, a screen and a USB stick.

We are using Raspberry Pi Imager. We have a more detailed tutorial for imaging the Pi.

1. Download the Video Looper Image

You can download the Video Looper image here. Choose the latest version that is compatible with the Pi model you are using, please refer to the "works with all boards up to" column.

videoLooper.png

2. Using Raspberry Pi Imager

  1. Raspberry Pi Device select Raspberry Pi Model
  2. Storage select the SD card

imager.png

  1. Operation System - select Use custom - select the newly downloaded Video Looper Image customImage.png

3. Files Format

Video Looper uses the default video player, omxplayer, which can play most videos encoded with the H.264 video codec and in a video format with an extension like .avi, .mov, .mkv, .mp4, or .m4v.

Try to minimize the size of your files and export the video with the exact resolution of your display for better performance. e.g. You shouldn't use an uncompressed 4K video format on a 1080p HD display.

4. Plug and Play

You can put your video on a USB stick and plug it to the pi. Your video(s) is ready to loop!

If only one movie is available it will play continually in a loop.

If multiple movies are found then each movie will be played in alphabetical order by filename and will loop back to the first video and play all videos again in order repeatedly.

Raspberry Pi Image

How to Configure a Raspberry Pi for the first time

Once your Raspberry Pi is imaged, it is ready to go! We have a more detailed tutorial for imaging the Pi. Now we can move on to configuration when you turn on your Pi for the first time.

1. Power up the Raspberry Pi

When you plug in the power supply and all other equipment you need, the Pi should start booting automatically. If your Raspberry Pi does not turn on within 5 minutes, check the status LED, and try re-image the SD card.

If everything goes right, you should see this.

start.png

2. Locale

You need to set your country, language, time zone, and keyboard layout.

locale.png

When you are setting up the keyboard, make sure the keyboard is plugged in. If you uncheck the Use US keyboard, it will set up the keyboard corresponding to your Country. The main difference between US and UK keyboards is the positions of @,", £ and #. There are many variants of keyboards, even just for US/UK keyboards. You can change that after the initial setup. Check this tutorial for changing the keyboard layout.

3. User

You can set your username and password here. For some older Raspberry Pi OS, it has a default username and password, which is username: [ pi ] ; password: [ raspberry ].

user.png

4. Wifi

You can log in to the WIFI as usual with SSID and password. For some networks, such as UAL wifi, you need to sign in with your UAL account, which will not work for most Pi. In that case, you will need an Ethernet cable to access to the internet.

network.png

5. Brower

Google Chrome and Firefox are both preinstalled, you just need to choose one as your default browser. You can still access the other run from the start menu. browser.png

Raspberry Pi comes with many essential applications pre-installed so you can start using them straight away, such as Thonny. You can go to Start - Preference - Recommended Software, explore the list and download the ones you need.

recommended-software.png

Tutorials

Tutorials

How to make the Raspberry Pi display a web page fullscreen at power on

This short tutorial should be enough for you to be able to setup a Raspberry Pi with GUI mode and auto login enabled to disable a web page full screen automatically when it turns on.

  1. Copy full-screen.sh into the home folder of the pi user, and run the following command: /home/pi/full-screen.sh

sudo chmod +x full-screen.sh

full-screen.sh

export DISPLAY=:0.0
xset s off
xset -dpms
xset s noblank
chromium-browser --noerrdialogs --kiosk https://google.co.uk --incognito
  1. Create a folder called autorun inside the .config folder of the home folder of the pi user: /home/pi/.config/autorun/kiosk.desktop

cd /home/pi/.config mkdir autorun

kiosk.desktop

[Desktop Entry]
Type=Application
Exec=/home/pi/full-screen.sh
Hidden=false
X-GNOME-Autostart-enabled=true
Name=kiosk
  1. Reboot the Raspberry Pi.

sudo reboot now

Tutorials

How to power the Raspberry Pi Pico

Powering the Raspberry Pi Pico

The easiest way to power a Pico is through the USB cable either to a computer or a phone charger. If you are going for a wireless design, you can use batteries as well. This tutorial will demonstrate how to power a Pico with a 9V battery or 3 AA batteries.

Raspberry Pi Pico pinout

You have to find out the pinout of the model you are using. The pins you are looking for are VSYS and GND. In this tutorial, a Pico W is used.

Raspberry Pi Pico's Power Need

VSYS (PIN 39): Pin for main system input voltage. The input voltage can vary between 1.8V to 5.5V. This voltage is used by the onboard SMPS to generate 3.3V to power the RP2040 microcontroller and GPIOs.

Why these parts are needed

9V battery

Part needed: switch, LM7805 & Any diode

pi-9v.png

3 AA batteries

Part needed: switch & Any diode 3AAPico.png

Tutorials

How to make two Raspberry Pi Pico communicate via Wifi

Wifi Communication

Before heading to communication between two pico, you can try controlling pico via wifi with your computer first, see tutorial here.

Server Code

Client Code

Tutorials

How to control Raspberry Pi Pico via Wifi

What is Wifi

WiFi, short for Wireless Fidelity, is a technology that enables devices like smartphones, laptops, and other electronic gadgets to connect to the internet or communicate with each other without the need for physical cables. It operates by using radio frequency signals to transmit data between devices and a wireless router. The router, connected to the internet via a wired connection, acts as a central hub that facilitates communication between devices within its range. WiFi has become a ubiquitous and convenient way for people to access the internet and share information wirelessly, contributing to the proliferation of wireless connectivity in homes, businesses, and public spaces.

You can create a local wifi network with just powering up a wifi router. When two or more devices (computers, microcontrollers...) are connected to the same wifi network, they can communicate with each other, without accessing the internet. Not all microcontrollers come with a built-in Wifi module so we will be using Pico W (with a built-in wifi module) in this tutorial. But there are plenty of add-ons options you can add to your microcontroller for wifi.

External read for fun:)

What is IP address

An IP address, or Internet Protocol address, is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It consists of a series of numbers separated by periods, like xxx.xxx.xxx.xxx. Think of it as a digital address for your device on the internet. It allows devices to identify and communicate with each other on a network, much like a home address allows mail to be delivered to a specific location. IP addresses can be dynamic, meaning they change periodically, or static, where they remain constant. They play a crucial role in routing data packets across the internet, ensuring that information reaches the correct destination.

How to find my IP address

  1. Google Search - "What's my IP address?"
  2. Go to Network Preferences (MAC), Wifi Properties (Windows)
  3. Go to Terminal (MAC) or Command Prompt (Windows) and type in ipconfig getifaddr en1

Get started

The example code will turn on/off the onboard LED on Pico via wifi without an external circuit. See this tutorial to learn how to set up your Pico. Before you go ahead, there are some things that you need to change for your wifi.

  1. Change ssid, password in the code
  2. Run your code in Thonny
  3. Find your IP address in the Thonny Shell, something like ip = 10.3.15.120
  4. open up a web browser
  5. go to http:// **IP address**/light/on to turn the LED on
  6. go to http:// **IP address**/light/off to turn the LED off
import network
import socket
import time

from machine import Pin

led = Pin("LED", Pin.OUT)

ssid = 'YOUR NETWORK NAME'
password = 'YOUR NETWORK PASSWORD'

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect(ssid, password)

html = """<!DOCTYPE html>
<html>
    <head> <title>Pico W</title> </head>
    <body> <h1>Pico W</h1>
        <p>%s</p>
    </body>
</html>
"""

max_wait = 10
while max_wait > 0:
    if wlan.status() < 0 or wlan.status() >= 3:
        break
    max_wait -= 1
    print('waiting for connection...')
    time.sleep(1)

if wlan.status() != 3:
    raise RuntimeError('network connection failed')
else:
    print('connected')
    status = wlan.ifconfig()
    print( 'ip = ' + status[0] ) //print your address

addr = socket.getaddrinfo('0.0.0.0', 80)[0][-1]

s = socket.socket()
s.bind(addr)
s.listen(1)

print('listening on', addr)

# Listen for connections
while True:
    try:
        cl, addr = s.accept()
        print('client connected from', addr)
        request = cl.recv(1024)
        print(request)

        request = str(request)
        led_on = request.find('/light/on')
        led_off = request.find('/light/off')
        print( 'led on = ' + str(led_on))
        print( 'led off = ' + str(led_off))

        if led_on == 6:
            print("led on")
            led.value(1)
            stateis = "LED is ON"

        if led_off == 6:
            print("led off")
            led.value(0)
            stateis = "LED is OFF"

        response = html % stateis

        cl.send('HTTP/1.0 200 OK\r\nContent-type: text/html\r\n\r\n')
        cl.send(response)
        cl.close()

    except OSError as e:
        cl.close()
        print('connection closed')
Tutorials

How to install Node.js on Raspberry Pi

Installing Node.js on Raspberry Pi is very simple for those with basic command line experience.

In the terminal or via SSH:

  1. Add the package source: curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
  2. Install Node using: sudo apt-get install -y nodejs
  3. Confirm package is installed: node -v

Extra steps

You may also wish to install the development tools to build native addons: sudo apt-get install gcc g++ make

And you may wish to install Yarn package manager to replace NPM:

curl -sL https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt-get update && sudo apt-get install yarn

Pi War 2024 Log

Documentation of Pi War 2024

Pi Wars is an international, challenge-based robotics competition in which teams build Raspberry Pi-controlled robots and then compete in various non-destructive challenges to earn points.

28ecda96-29b5-4daf-a60e-21a281f9ad4d.JPG

Planning

We planned to build a four-wheel robot car which is driven by two TT motors and Raspberry Pi Pico W. We will use a second Raspberry Pi Pico W and two joysticks for the remote controller. The car and the controller will communicate via WiFi.

Image.jpeg

Circuit

Car Circuit

We used a 5V regulator LM7805 to regulate 9V from the 9V battery to 5V to power up the Raspberry Pico via the VSYS and GND pins. A diode between VSYS and 5V output to present backfeeding. More about powering Pico.

We used a second 9V battery to power up two TT motors, both power sources share the same ground.

We used an L293D IC for controlling two motors. GPIO10 and GPIO11 pins control the directions of the left motor and GPIO14 and GPIO15 pins control the directions of the right motor. More about L293D IC.

picoCarCircuit.png

Controller Circuit

We use the same 5V regulator LM7805 to regulate the power supply for Raspberry Pico, and connect two joysticks's data pins with pins GPIO26 and GPIO27. One joystick controls left and right, and the other controls forward and backwards.

Problems with batteries

This is a remote-controlled robot car so it needs to be wireless and must use battery as its power supply. However, the battery is not a stable power supply which cannot supply a constant stable 9V to both the motors and Pico. Even when the battery is not completely dry, it may become insufficient to turn on the Pico when the voltage drops below a certain point. The same problem goes for the motors but is less fatal, as the motors can still run, just slower.

This time, we just decided to change batteries more often, but it is not environmentally friendly or efficient. We will look into power banks with a low-current charging mode.

Python Code

All codes can be found on our Github page.

Testing two motors
import time

from machine import Pin

motor1a = Pin(14, Pin.OUT)
motor1b = Pin(15, Pin.OUT)

motor2a = Pin(10, Pin.OUT)
motor2b = Pin(11, Pin.OUT)

print("Hello.")


def right_forward():
    motor1a.value(0)
    motor1b.value(0)
    motor2a.value(0)
    motor2b.value(1)


def left_forward():
    motor2a.value(0)
    motor2b.value(0)
    motor1a.value(1)
    motor1b.value(0)


def right_backward():
    motor1a.value(0)
    motor1b.value(0)
    motor2a.value(1)
    motor2b.value(0)


def left_backward():
    motor2a.value(0)
    motor2b.value(0)
    motor1a.value(0)
    motor1b.value(1)


def forward():
    motor1a.value(1)
    motor1b.value(0)
    motor2a.value(0)
    motor2b.value(1)


def backward():
    motor1a.value(0)
    motor1b.value(1)
    motor2a.value(1)
    motor2b.value(0)


def stop():
    motor1a.value(0)
    motor1b.value(0)
    motor2a.value(0)
    motor2b.value(0)
Testing two joysticks
import time

from machine import ADC, Pin

HIGH = 35000
LOW = 30000


def is_still(val):
    return val > LOW and val < HIGH


def increase(val):
    return val > HIGH


def decrease(val):
    return val < LOW


joystick_y = ADC(Pin(26))
joystick_x = ADC(Pin(27))

STOP = 1
STRAIGHT_FORWARD = 2
RIGHT_FORWARD = 3
LEFT_FORWARD = 4
RIGHT_BACKWARD = 5
LEFT_BACKWARD = 6
STRAIGHT_BACKWARD = 7


while True:
    x_val = joystick_x.read_u16()
    y_val = joystick_y.read_u16()

    x_still = is_still(x_val)
    y_still = is_still(y_val)

    x_increase = increase(x_val)
    y_increase = increase(y_val)

    x_decrease = decrease(x_val)
    y_decrease = decrease(y_val)

    if x_still and y_still:
        print(STOP)

    if y_increase and x_still:
        print(STRAIGHT_FORWARD)

    if y_decrease and x_still:
        print(STRAIGHT_BACKWARD)

    if y_increase and x_increase:
        print(LEFT_FORWARD)

    if y_increase and x_decrease:
        print(RIGHT_FORWARD)

    if y_decrease and x_increase:
        print(LEFT_BACKWARD)

    if y_decrease and x_decrease:
        print(RIGHT_BACKWARD)

    time.sleep(0.1)

When using wifi communication, the controller will be the server and the car will be the client.

Testing wifi communication - SERVER
import random
import socket
import time

import network
from machine import ADC, Pin

ssid = "WIFI_NAME"
password = "WIFI_PASSWORD"

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect(ssid, password)

# Wait for connect or fail
max_wait = 10
while max_wait > 0:
    if wlan.status() < 0 or wlan.status() >= 3:
        break
    max_wait -= 1
    print("waiting for connection...")
    time.sleep(1)
# Handle connection error
if wlan.status() != 3:
    raise RuntimeError("network connection failed")
else:
    print("connected")
    status = wlan.ifconfig()
    # print('ip = ' + status[0])

# Open socket
addr = socket.getaddrinfo("0.0.0.0", 80)[0][-1]

s = socket.socket()
s.bind(addr)
s.listen(1)

print("listening on", addr)

# Listen for connections
while True:
    try:
        cl, addr = s.accept()
        request = cl.recv(1024)
        print(request)
        # No need to unpack request in this example
        ran_num = str(random.randint(0, 100))
        cl.send(ran_num)
        print("Sent: " + ran_num)
        cl.close()

    except OSError as e:
        cl.close()
        print("connection closed")
Testing wifi communication - CLIENT

Make sure you change the IP address of your pi, which you can find in the console when you run the above server code.

import random
import socket
import time

import network
from machine import ADC, Pin

ssid = "WIFI_NAME"
password = "WIFI_PASSWORD"

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect(ssid, password)

# Wait for connect or fail
max_wait = 10
while max_wait > 0:
    if wlan.status() < 0 or wlan.status() >= 3:
        break
    max_wait -= 1
    print("waiting for connection...")
    time.sleep(1)
# Handle connection error
if wlan.status() != 3:
    raise RuntimeError("network connection failed")
else:
    print("connected")
    status = wlan.ifconfig()
    # print('ip = ' + status[0])

while True:
    ai = socket.getaddrinfo("192.168.1.115", 80)  # Address of Web Server
    addr = ai[0][-1]

    # Create a socket and make a HTTP request
    s = socket.socket()  # Open socket
    s.connect(addr)
    s.send(b"Anything")  # Send request
    ss = str(s.recv(512))  # Store reply
    # Print what we received
    print(ss)
    # Set RGB LED here
    s.close()  # Close socket
    time.sleep(0.2)  # wait
Final code for controller - SERVER
import socket
import time

import network
from machine import ADC, Pin

HIGH = 35000
LOW = 30000


def is_still(val):
    return val > LOW and val < HIGH


def increase(val):
    return val > HIGH


def decrease(val):
    return val < LOW


joystick_y = ADC(Pin(26))
joystick_x = ADC(Pin(27))
led = Pin("LED", Pin.OUT)

STOP = 1
STRAIGHT_FORWARD = 2
RIGHT_FORWARD = 3
LEFT_FORWARD = 4
RIGHT_BACKWARD = 5
LEFT_BACKWARD = 6
STRAIGHT_BACKWARD = 7

ssid = "WIFI_NAME"
password = "WIFI_PASSWORD"

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect(ssid, password)

# Wait for connect or fail
max_wait = 10
while max_wait > 0:
    if wlan.status() < 0 or wlan.status() >= 3:
        break
    max_wait -= 1
    print("waiting for connection...")
    time.sleep(1)
# Handle connection error
if wlan.status() != 3:
    raise RuntimeError("network connection failed")
else:
    print("connected")
    status = wlan.ifconfig()
    print('ip = ' + status[0])
    led.on()
    

# Open socket
addr = socket.getaddrinfo("0.0.0.0", 80)[0][-1]

s = socket.socket()
s.bind(addr)
s.listen(1)

print("listening on", addr)

while True:
    try:
        cl, addr = s.accept()
        request = cl.recv(1024)
        print("request", request)

        # print("loop")
        x_val = joystick_x.read_u16()
        y_val = joystick_y.read_u16()

        x_still = is_still(x_val)
        y_still = is_still(y_val)

        x_increase = increase(x_val)
        y_increase = increase(y_val)

        x_decrease = decrease(x_val)
        y_decrease = decrease(y_val)

        if x_still and y_still:
            print(STOP)
            cl.send(str(STOP))

        if y_increase and x_still:
            print(STRAIGHT_FORWARD)
            cl.send(str(STRAIGHT_FORWARD))

        if y_decrease and x_still:
            print(STRAIGHT_BACKWARD)
            cl.send(str(STRAIGHT_BACKWARD))

        if y_increase and x_increase:
            print(LEFT_FORWARD)
            cl.send(str(LEFT_FORWARD))

        if y_increase and x_decrease:
            print(RIGHT_FORWARD)
            cl.send(str(RIGHT_FORWARD))

        if y_decrease and x_increase:
            print(LEFT_BACKWARD)
            cl.send(str(LEFT_BACKWARD))

        if y_decrease and x_decrease:
            print(RIGHT_BACKWARD)
            cl.send(str(RIGHT_BACKWARD))

        cl.close()

    except Exception as e:
        print(e)
        cl.close()
        print("connection closed")

    time.sleep(0.1)
Final code for car - CLIENT
import random
import socket
import time

import network
from machine import ADC, Pin

motor1a = Pin(14, Pin.OUT)
motor1b = Pin(15, Pin.OUT)

motor2a = Pin(10, Pin.OUT)
motor2b = Pin(11, Pin.OUT)

led = Pin("LED", Pin.OUT)

ssid = "WIFI_NAME"
password = "WIFI_PASSWORD"

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect(ssid, password)

# Wait for connect or fail
max_wait = 10
while max_wait > 0:
    if wlan.status() < 0 or wlan.status() >= 3:
        break
    max_wait -= 1
    print("waiting for connection...")
    time.sleep(1)
# Handle connection error
if wlan.status() != 3:
    raise RuntimeError("network connection failed")
else:
    print("connected")
    status = wlan.ifconfig()
    print('ip = ' + status[0])
    led.on()


def right_forward():
    motor1a.value(0)
    motor1b.value(0)
    motor2a.value(0)
    motor2b.value(1)


def left_forward():
    motor2a.value(0)
    motor2b.value(0)
    motor1a.value(1)
    motor1b.value(0)


def right_backward():
    motor1a.value(0)
    motor1b.value(0)
    motor2a.value(1)
    motor2b.value(0)


def left_backward():
    motor2a.value(0)
    motor2b.value(0)
    motor1a.value(0)
    motor1b.value(1)


def forward():
    motor1a.value(1)
    motor1b.value(0)
    motor2a.value(0)
    motor2b.value(1)


def backward():
    motor1a.value(0)
    motor1b.value(1)
    motor2a.value(1)
    motor2b.value(0)


def stop():
    motor1a.value(0)
    motor1b.value(0)
    motor2a.value(0)
    motor2b.value(0)


commands = {
    "1": stop,
    "2": forward,
    "3": right_forward,
    "4": left_forward,
    "5": right_backward,
    "6": left_backward,
    "7": backward,
}

while True:
    ai = socket.getaddrinfo("192.168.0.100", 80)  # Address of Web Server
    addr = ai[0][-1]

    # Create a socket and make a HTTP request
    s = socket.socket()  # Open socket
    s.connect(addr)
    s.send(b"Anything")  # Send request
    ss = s.recv(512).decode()  # Store reply
    # Print what we received
    try:
        commands[ss]()
    except KeyError:
        commands["1"]()

    # Set RGB LED here
    s.close()  # Close socket
    time.sleep(0.2)  # wait

Router Setting

In general, if both the server pico and the client pico are connected to the same wifi network, they can communicate. However, most routers provide a dynamic IP address which may change every time, based on the number of devices connected and which device is connected to the network first. We only used the router for the controller and the car in the beginning, and we started to experience problems when there were other devices connected to our router.

Therefore, we need to reserve IP addresses for the controller and the car, to make sure they are listening to the right address. This process may be different based on what router you are using.

You may see something similar like this:

Car Design

The car is Princess Peach-inspired, so very pink. We laser-cut serval layers to form the main body of the car.

Problems with back wheels

We have four identical wheels. However, the rubber surface of the back wheels has created too much friction which the front wheels are not powerful enough to pull. In the end, we needed to remove the rubber bit of the back wheels.

Controller Design

Continue with the Princess Peach theme, the controller is a heart-shaped box with holes for the on-off button and two joysticks.

Screenshot 2024-04-19 at 16.56.06.png Screenshot 2024-04-19 at 16.56.16.png

Final Controller!

Screenshot 2024-04-19 at 17.23.31.png Screenshot 2024-04-19 at 17.20.45.png

Testing!

Competition Day Snaps

Challenge 1 - Pi Noon: The Hindenburg Disaster

We need to poke the balloons on our opponent. This is our opponent, Dangly TOO!

148f9663-64b1-40a7-b608-a307e1c1b1dc.JPG 64776656-2eed-49f8-b11f-9585cbcc2b28.JPG

Challenge 2 - Eco Disaster

We need to put the green barrels in the blue square and the red barrels in the yellow square. There were some impressive robots doing it autonomously!

Screenshot 2024-04-22 at 10.31.37.png

Challenge 3 - Minesweeper

We need to go to the red lightbox as fast as we can.

Screenshot 2024-04-22 at 10.33.55.png

Challenge 4 - Escape Route

We need to escape the maze without looking at it.

IMG_4342.JPG

Challenge 5 - The Zombie Apocalypse
Challenge 6 - The Temple of Doom

This is the hardest and the most unexpected challenge of all. Unfortunately, Edwina is not built for this, so we didn't finish the course.

IMG_4338.JPG