Week 04 — Embedded Programming

Overview

The assignment this week was to browse the datasheet of a microcontroller and write a program that interacts with input and output devices.

I used the Seeed Studio XIAO RP2040 together with Arduino IDE. The week started with a simple blink test and gradually expanded into experiments using an external LED, push button input, a sound sensor module, a servo motor and a potentiometer.

By building small experiments step by step I was able to understand how a microcontroller reads inputs, processes logic and controls hardware outputs.

Learning Process

At the beginning of the week I was not familiar with the workflow of the XIAO RP2040. I needed to understand how to install the correct board package in Arduino IDE and how the uploading process works.

After reading documentation and watching tutorials I successfully configured the board and started testing basic programs. From there I gradually added more hardware components and tested them one by one.

Group Assignment

For the group assignment, we worked at the Litchee Lab (Shenzhen, China) and explored embedded programming workflows while comparing development environments, toolchains, and hardware architectures. The goal was to understand how software interacts with microcontrollers through different levels of abstraction.

Arduino IDE Installation

We began by installing Arduino IDE (version 2.3.8), which provides an integrated development environment including code editing, compilation, library management, and uploading.

Compared to traditional embedded development environments, Arduino IDE simplifies the workflow by integrating the toolchain and reducing setup complexity.

Adding RP2040 Support (Boards Manager)

Since RP2040-based boards are not included by default, we used the Boards Manager to install the required support package.

We accessed: Tools → Board → Boards Manager and searched for RP2040.

We installed: Raspberry Pi Pico/RP2040/RP2350, which provides support for RP2040-based boards.

After installation, we selected the board: Seeed Studio XIAO RP2040.

Hardware and Pinout Understanding

To better understand how the microcontroller interacts with hardware, we analyzed the physical structure and pinout of the XIAO RP2040.

The board includes a USB-C interface, a built-in RGB LED, a power LED, and BOOT and RESET buttons. These components support debugging and control.

Each pin can support multiple functions such as digital I/O, analog input, I2C, SPI, and UART. Understanding the mapping between labeled pins (D pins) and GPIO numbers was essential.

All digital pins (D0–D10) support PWM output, which means any of these pins can be used to control a servo motor.

This understanding helped avoid wiring mistakes and ensured correct communication between software and hardware.

Workflow Comparison

We compared Arduino IDE with lower-level embedded development approaches.

• Arduino IDE: easy setup, fast prototyping, high-level functions
• Low-level programming: more control over hardware but more complex workflow

Arduino abstracts many low-level details such as register access, making embedded programming more accessible while still enabling interaction with real hardware.

Conclusion

This assignment helped us understand the full embedded development workflow, from environment setup to program upload and hardware interaction. It also clarified how high-level tools relate to the underlying system.

Group assignment link: View group documentation

Programming Experiments

I approached this week as a sequence of small experiments. Each experiment helped me understand a different part of embedded programming.

1. Blink — Built-in LED

void setup(){
pinMode(LED_BUILTIN, OUTPUT);
}

void loop(){
digitalWrite(LED_BUILTIN, HIGH);
delay(1000);
digitalWrite(LED_BUILTIN, LOW);
delay(1000);
}

2. External LED

int led = 3;

void setup(){
pinMode(led, OUTPUT);
}

void loop(){

digitalWrite(led, HIGH);
delay(1000);

digitalWrite(led, LOW);
delay(1000);

}

3. Button Controlling LED

const int buttonPin = 28;
const int ledPin = 3;

void setup(){

pinMode(ledPin, OUTPUT);
pinMode(buttonPin, INPUT_PULLUP);

}

void loop(){

int buttonState = digitalRead(buttonPin);

if(buttonState == LOW){
digitalWrite(ledPin, HIGH);
}
else{
digitalWrite(ledPin, LOW);
}

}

4. Sound Sensor Toggle LED

const int soundPin = 28;
const int ledPin = 3;

bool ledState = false;
bool lastSoundState = HIGH;

unsigned long lastTriggerTime = 0;
const unsigned long debounceTime = 300;

void setup(){

pinMode(ledPin, OUTPUT);
pinMode(soundPin, INPUT);

digitalWrite(ledPin, LOW);

}

void loop(){

bool soundState = digitalRead(soundPin);
unsigned long now = millis();

if(soundState == LOW && lastSoundState == HIGH){

if(now - lastTriggerTime > debounceTime){

ledState = !ledState;

digitalWrite(ledPin, ledState ? HIGH : LOW);

lastTriggerTime = now;

}

}

lastSoundState = soundState;

}

5. Servo Sweep

#include <Servo.h>

Servo myservo;

int pos = 30;

void setup(){

myservo.attach(1);

}

void loop(){

for(pos = 30; pos <= 150; pos++){

myservo.write(pos);
delay(10);

}

for(pos = 150; pos >= 30; pos--){

myservo.write(pos);
delay(10);

}

}

6. Potentiometer Controlling Servo

#include <Servo.h>

Servo myservo;

const int potPin = A0;
const int servoPin = 1;

void setup(){

myservo.attach(servoPin);

}

void loop(){

int potValue = analogRead(potPin);

int angle = map(potValue,0,1023,0,180);

myservo.write(angle);

delay(20);

}

Reflection

This week helped me understand how embedded systems connect software and hardware. Simple programs like Blink are useful for verifying that the board works, while sensors and actuators demonstrate how the microcontroller interacts with the environment.

The most interesting part for me was combining sensors and outputs, such as the sound module toggling an LED and the potentiometer controlling a servo motor.