Weekly Assignments:

Check Out Our Group Assignment

Group assignment:

• Demonstrate and compare the toolchains and development workflows for available embedded architectures

• Document your work to the group work page and reflect on your individual page what you learned

Individual assignment:

• Browse through the datasheet for a microcontroller

• Write and test a program for an embedded system using a microcontroller to interact (with local input &/or output devices) and communicate (with remote wired or wireless connections)

Bill of Materials

Core Board

• Raspberry Pi Pico W

• Micro-USB cable

For Experiments

• Breadboard

• Jumper wires (Male-Male, Male-Female)

• LEDs (5mm)

• Servo motor (SG90 recommended)

• HC-SR04 Ultrasonic sensor

• L298N Motor driver module

• DC motor

• External 5–9V battery (for motor driver)

Introduction to the Raspberry Pi Pico W

Source: Raspberry Pi Website

The RP2040 Microcontroller:

The Pico W is built around the:

RP2040 microcontroller (designed by Raspberry Pi)

Core Processor Specifications

Advanced Feature: PIO (Programmable IO) This is what makes RP2040 special. It allows you to create custom hardware protocols in software.

You can:

• Create custom communication protocols

• Drive displays

• Generate precise signals

Model Comparison: Pico vs. Pico W

The Pico W includes:

Infineon CYW43439

Supports:

• 2.4 GHz WiFi

• Bluetooth Low Energy (BLE)

It communicates internally with RP2040 using SPI.

Technical Specifications

Hardware Architecture

Source: www.mischianti.org

Pinout Overview

The Pico W has:

• 40 pins total

• 26 GPIO pins

• 3 ADC pins

• Power pins

• Ground pins

Power Pins

Safety & Power (VERY IMPORTANT)

3.3V LOGIC ONLY

The Pico W GPIO pins:

• MAX voltage: 3.3V

• If you connect 5V → you can permanently damage the board

Power Paths Explained

USB plugged → 5V on VBUS

• VSYS feeds onboard regulator

• Regulator outputs stable 3.3V

• Never power motors directly from Pico.

GPIO Capabilities

Each GPIO can:

• Digital input

• Digital output

• PWM

• I2C

• SPI

• UART

ADC pins:

• GP26

• GP27

• GP28

Initial Setup & Firmware

Flashing MicroPython (BOOTSEL Method)

1. Hold BOOTSEL button

2. Plug USB into computer

3. Release BOOTSEL

4. A drive appears named:

RPI-RP2

5. Drag MicroPython UF2 file into it (Access MicroPython UF2 From Here)

6. Board reboots automatically

You’re done.

Setup Thonny IDE

1. Install Thonny (Download Thonny From Here)

2. Open Thonny

3. Go to:

Tools → Options → Interpreter

4. Select:

MicroPython (Raspberry Pi Pico)

5. Choose correct COM port

6. Click OK

You should now see:

>>>

REPL prompt.

Experimenting with Our Microcontroller

Blink Onboard LED

The Pico W onboard LED is connected differently than standard Pico.

On Pico W, LED is controlled through wireless chip.

PHASE 1 – Blink Code

import network
import time
from machine import Pin

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

while True:
    led.toggle()
    time.sleep(0.5)

Run it.

If LED blinks → your environment is correct.

Pico W Blink Video

Blink External Led

Wiring

PHASE 2 – External LED Blink Code

from machine import Pin
import time

led = Pin(15, Pin.OUT)

while True:
    led.on()
    time.sleep(1)
    led.off()
    time.sleep(1)

Run it and see if the external led blinks

Be careful to not put resistor’s legs with led’s legs

Pico W Led Blink Video

Building a Pico Car

DC Motor + LED

In this experiment, we control:

• An LED (visual feedback)
• A DC motor using the L298N motor driver

The system demonstrates:

• GPIO output control
• Motor direction switching
• Timing-based behavior

Components Used

Wiring

LED Connection

Motor Driver (L298N)

Important:

• Do NOT power the motor from the Pico

• Always use an external power supply

Control Logic

from machine import Pin
import time

# LED setup
led = Pin(16, Pin.OUT)

# Motor control pins
motor_in1 = Pin(14, Pin.OUT)
motor_in2 = Pin(15, Pin.OUT)

while True:
    # LED ON + Motor Forward
    led.on()
    motor_in1.value(1)
    motor_in2.value(0)
    time.sleep(2)

    # Motor Backward
    motor_in1.value(0)
    motor_in2.value(1)
    time.sleep(2)

    # Stop everything
    motor_in1.value(0)
    motor_in2.value(0)
    led.off()
    time.sleep(1)

Here, the LED turns ON when the system is active. The motor rotates forward for 2 seconds. Then backward for 2 seconds. Then stops for 1 second. The loop repeats indefinitely.

Rotating the Car (180° Left & Right)

In this experiment, we use two DC motors to rotate the car in place:

• Rotate right (180°)
• Rotate left (180°)

This is done by making both motors spin in the same direction, causing the robot to pivot instead of moving forward.

Components Used

Wiring (Motors)

Control Logic

Rotate Right (Clockwise)

Rotate Left (Counterclockwise)

Since both motors spin the same way, the robot spins in place instead of moving forward.

from machine import Pin
import time

# Motor 1
motor1_in1 = Pin(14, Pin.OUT)
motor1_in2 = Pin(15, Pin.OUT)

# Motor 2
motor2_in1 = Pin(16, Pin.OUT)
motor2_in2 = Pin(17, Pin.OUT)

def stop():
    motor1_in1.value(0)
    motor1_in2.value(0)
    motor2_in1.value(0)
    motor2_in2.value(0)

def rotate_right():
    # Both motors forward
    motor1_in1.value(1)
    motor1_in2.value(0)
    motor2_in1.value(1)
    motor2_in2.value(0)
    time.sleep(2)
    stop()

def rotate_left():
    # Both motors backward
    motor1_in1.value(0)
    motor1_in2.value(1)
    motor2_in1.value(0)
    motor2_in2.value(1)
    time.sleep(2)
    stop()

while True:
    rotate_right()
    time.sleep(1)

    rotate_left()
    time.sleep(1)

Here, The robot Spins right for 2 seconds (~180°). Stops briefly. Spins left for 2 seconds (~180°). This loop continues forever.

Pico W Rotation Video

Rotate

L298N Motor Driver Architecture

The L298N is a motor driver that lets a microcontroller (like the Pico) control DC motors safely and efficiently.

Why do we need it?

• GPIO pins → very low power
• Motors → need high current + higher voltage

The L298N acts as a power bridge between them.

Core Idea: H-Bridge

At the heart of the L298N is something called an H-Bridge.

This circuit lets you:

• Spin a motor forward
• Spin it backward

Direction Control

Key Pins Overview

Control Pins

Output Pins

Power Pins

Speed Control (PWM)

The ENA / ENB pins can take a PWM signal.

This allows:

• Slow motor → low duty cycle
• Fast motor → high duty cycle

This is how you control speed, not just ON/OFF.

Important Characteristics

• Voltage range: ~4.5V to 46V
• Current: ~2A per motor
• Built-in protection diodes
• Can control 2 motors at once

Limitations (Very Important)

The L298N is not very efficient.

• Uses older transistor design (BJT)
• Loses energy as heat
• Efficiency: ~40–50%

That’s why it can get hot.

Better Alternatives

• TB6612FNG
• L293D (slightly better)

But:

L298N is still great for learning and prototyping.

Program Code Example:

from machine import Pin
import time

# Motor control pins
motor_in1 = Pin(14, Pin.OUT)
motor_in2 = Pin(15, Pin.OUT)

def rotate_motor_right():
    motor_in1.value(1)
    motor_in2.value(0)
    print("Motor rotating right (clockwise)")

def rotate_motor_left():
    motor_in1.value(0)
    motor_in2.value(1)
    print("Motor rotating left (counterclockwise)")

while True:
    rotate_motor_right()
    time.sleep(2)

    rotate_motor_left()
    time.sleep(2)

Power Management (Pico + L298N + 2 Motors)

When working with motors, power is the #1 thing that can go wrong.

• Motors need high current
• Pico provides very low current

If you power things incorrectly, you can:

• Reset the Pico
• Overheat the driver
• Damage components

Power Distribution

Pico Power

Motor Power (Through L298N)

Overall Look After All These Steps

Files

You can access to the files of this week from the link below.

Week 4 Files