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Week 4 Assignments - Embedded Programming

Group Assignment

The group assignment for this week was to:

  • 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

Outcomes

The group assignment page for this week is on the 2025 Charlotte Super Fab Lab group site for Week 4 - Embedded Programming.

What Was Learned

In the group assignment, we considered toolchains and development workflows for the XIAO boards with both the Arduino IDE and Circuit Python. We were able to set up the software / development environments needed, set up the XIAO board appropriately, and use the environments to run basic programs for controlling LEDs. This provided us experience on:

  • How to set up different development environments for use with microcontroller boards
  • How to set up the set up a microcontroller to run software environments like circuit python
  • How to use use development environments / IDEs to program microcontroller boards

Individual Assignment

The individual assignment for this week was to:

  • Browse through the datasheet for your microcontroller
  • Write a program for a microcontroller, and simulate its operation, to interact (with local input and/or output devices) and communicate (with remote wired or wireless connection)

Outcomes

Microcontroller Documentation Review

I selected the XIAO ESP32C3 as the microcontroller board to explore. I selected this board, because it has more robust microcontroller functionality as well as integrated wireless communication that may be helpful for my final project.

XIAO ESP32C3 Microcontroller Board1

I reviewed two primary sources of documentation from the XIAO board manufacturer - Seeed Studio.

In review of the datasheet and documentation, I noted some of the main points of functionality / use for the XIAO ESP32C3.

XIAO ESP32C3 Microcontroller Board Front1

XIAO ESP32C3 Microcontroller Board Back1

  • There is a USB Type-C connector for primary development interaction with the board
  • The board is designed around the ESP32-C3 chip - a 32­bit RISC­-V single ­core processor that operates at up to 160 MHz
  • There are integrated WiFi and Bluetooth subsystems for wireless communication
  • The board also includes buttons for boot and reset, as well as a charge LED that can indicate board connection.
  • There are pad connections on the back of the board for battery (up to 3.7V) and other functions. For surface mount on a board this may need to be accounted for.

The board is configured for 3.3V logic, which is very important to note for working with inputs / outputs.

Pinout diagram for the XIAO ESP32C31

There are 14 pins available for connection. Some pins support multiple functions, but overall functionality available covers:

  • 3 pins for power functions - 5V, GND, 3.3V
  • 10 pins could be used for Digital I/O (D0-D10)
  • 3 pins could be used for Analog I/O (A0-A2)
  • 2 pins could be used for I2C communication (SDA, SCL)
  • 2 pins could be used for UART communication (RX, TX)
  • 3 pins could be used for SPI communication (MOSI, MISO, SCK)

The wiki documentation provides sample code for a variety of basic setup and functionality. This includes:

  • Software setup with Arduino IDE
  • Sample setup / code for basic LED blinking

Programming Process

For exploring the microcontroller operation in simulation, I adopted the Arduino and C programming environment and process afforded by the Wokwi site for microcontroller simulation.

Simulated Board Programming - Interaction

I used the Wokwi site for microcontroller simulation. Wokwi supports the XIAO ESP32C3 as a microcontroller board for simulation, and I wanted to explore the use of the board. Wokwi has a specific section for ESP32 boards. The ESP32 section has a template for XIAO ESP32-C3.

The template for XIAO ESP32-C3 demonstrates a basic application for lighting up a Red, Green, and Blue LED in repeating sequence - each for a brief period of time.

Wokwi template for XIAO ESP32-C3

Wokwi Template for LED Sequence
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void setup() {
  Serial.begin(115200);
  pinMode(D2, OUTPUT);
  pinMode(D3, OUTPUT);
  pinMode(D4, OUTPUT);

  Serial.println("");
  Serial.println("Hello, XIAO ESP32-C3!");
  Serial.println("Welcome to Wokwi :-)");
}

void loop() {
  Serial.println("Red");
  digitalWrite(D2, HIGH);
  delay(500);
  digitalWrite(D2, LOW);

  Serial.println("Green");
  digitalWrite(D3, HIGH);
  delay(500);
  digitalWrite(D3, LOW);

  Serial.println("Blue");
  digitalWrite(D4, HIGH);
  delay(500);
  digitalWrite(D4, LOW);
}

To explore interaction connecting both inputs and outputs, I modified the Wokwi template for XIAO ESP32-C3. I explored connecting the inputs and outputs for the XIAO by accelerating the speed of the LED sequence in response to a button being pressed. I made the following changes:

  • Added a pushbutton
    • connected to the D0 pin for input reading
    • connection to 3.3V when pressed
    • connection to GND with pulldown resistor when not pressed
  • Revised the code to change speed in response to the pushbutton
    • set a default duration for each LED to display
    • check whether the button is pressed
    • if the button is pressed, set the duration to be shorter (faster run)

Pushbutton Accelerated LED Setup

Pushbutton Accelerated LED Sequence
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void setup() {
  Serial.begin(115200);
  pinMode(D0, INPUT);
  pinMode(D2, OUTPUT);
  pinMode(D3, OUTPUT);
  pinMode(D4, OUTPUT);

  Serial.println("");
  Serial.println("Hello, XIAO ESP32-C3!");
  Serial.println("Welcome to Wokwi :-)");
}

void loop() {

  int button = digitalRead(D0);
  Serial.print("Button value is: ");
  Serial.println(button);

  int pause = (button == HIGH) ? 100 : 500;

  Serial.println("Red");
  digitalWrite(D2, HIGH);
  delay(pause);
  digitalWrite(D2, LOW);

  Serial.println("Green");
  digitalWrite(D3, HIGH);
  delay(pause);
  digitalWrite(D3, LOW);

  Serial.println("Blue");
  digitalWrite(D4, HIGH);
  delay(pause);
  digitalWrite(D4, LOW);
}

Pushbutton Accelerated LED Sequence Demo

Simulated Board Programming - Communication

To explore communication, I considered the WiFi support for ESP32 provided by the Wowki simulator. WiFi support is documented at: Wokwi ESP32 WiFi Networking.

Wowki enables a simulation to connect to a virtual WiFi access point (Wowki-GUEST) in order to access internet connectivity.

The WiFi support page provides a set of project examples. The NTP Client example connects to an NTP server online in order to retrieve the current date and time. The NTP Client example uses a non-XIAO ESP32 developer kit board.

I reworked the NTP Client example from scratch in order to use the XIAO ESP32C3 board specifically and develop the WiFi simulation connectivity for the XIAO board. This employed an I2C connection to control an LCD, and so also explored LCD as an output for the XIAO board.

NTP Client XIAO ESP32C3 Setup

NTP WiFi Client for ESP-32
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// Learn about the ESP32 WiFi simulation in
// https://docs.wokwi.com/guides/esp32-wifi

#include <WiFi.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C LCD = LiquidCrystal_I2C(0x27, 16, 2);

#define NTP_SERVER     "pool.ntp.org"
#define UTC_OFFSET     0
#define UTC_OFFSET_DST 0

void spinner() {
  static int8_t counter = 0;
  const char* glyphs = "\xa1\xa5\xdb";
  LCD.setCursor(15, 1);
  LCD.print(glyphs[counter++]);
  if (counter == strlen(glyphs)) {
    counter = 0;
  }
}

void printLocalTime() {
  struct tm timeinfo;
  if (!getLocalTime(&timeinfo)) {
    LCD.setCursor(0, 1);
    LCD.println("Connection Err");
    return;
  }

  LCD.setCursor(8, 0);
  LCD.println(&timeinfo, "%H:%M:%S");

  LCD.setCursor(0, 1);
  LCD.println(&timeinfo, "%d/%m/%Y   %Z");
}

void setup() {
  Serial.begin(115200);

  LCD.init();
  LCD.backlight();
  LCD.setCursor(0, 0);
  LCD.print("Connecting to ");
  LCD.setCursor(0, 1);
  LCD.print("WiFi ");

  WiFi.begin("Wokwi-GUEST", "", 6);
  while (WiFi.status() != WL_CONNECTED) {
    delay(250);
    spinner();
  }

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());

  LCD.clear();
  LCD.setCursor(0, 0);
  LCD.println("Online");
  LCD.setCursor(0, 1);
  LCD.println("Updating time...");

  configTime(UTC_OFFSET, UTC_OFFSET_DST, NTP_SERVER);
}

void loop() {
  printLocalTime();
  delay(250);
}

NTP WiFi Client for XIAO ESP32C3 Demo

  1. https://wiki.seeedstudio.com/XIAO_ESP32C3_Getting_Started/ ↩↩↩↩