W10 — Output Devices

Before designing the PCB, I selected the components needed for this output device project: a servo motor as the mechanical actuator and an SMD tactile push button as the user input.

I designed the schematic in KiCad, expanding on the W09 board layout to add a servo motor connector. The XIAO ESP32-C3 drives the servo via its D3 PWM pin, while the SMD button on D1 remains as the user input.

After exporting Gerber files from KiCad, the PCB was fabricated and then populated with components. The SMD button was soldered first, followed by the servo connector and the XIAO ESP32-C3 module.

The firmware was written in Arduino IDE using the ESP32Servo library. The logic increments the servo angle by 10° with each button press, and resets to 0° after reaching 180°.

#include <ESP32Servo.h>

const int SERVO_PIN  = D3;
const int BUTTON_PIN = D1;

Servo myServo;
int currentAngle = 0;
bool lastButtonState = HIGH;

void setup() {
  Serial.begin(115200);
  delay(3000);

  pinMode(BUTTON_PIN, INPUT_PULLUP);

  myServo.attach(SERVO_PIN);
  myServo.write(currentAngle);

  Serial.println("=== Servo + Button Ready ===");
  Serial.print("Starting angle: ");
  Serial.println(currentAngle);
  Serial.println("Each button press = +10 degrees");
  Serial.println("Resets to 0 after reaching 180°");
}

void loop() {
  bool buttonState = digitalRead(BUTTON_PIN);

  // Detect press moment only (not hold)
  if (buttonState == LOW && lastButtonState == HIGH) {
    delay(50); // debounce
    buttonState = digitalRead(BUTTON_PIN);

    if (buttonState == LOW) {
      currentAngle += 10;

      // Reset to 0 after reaching 180
      if (currentAngle > 180) {
        currentAngle = 0;
        Serial.println(">>> Limit reached! Resetting to 0°");
      }

      myServo.write(currentAngle);

      Serial.print("Button PRESSED --> Servo at ");
      Serial.print(currentAngle);
      Serial.println("°");
    }
  }

  lastButtonState = buttonState;
  delay(10);
}

After uploading the firmware, I tested the board by pressing the button repeatedly to verify:

1. Each press rotates the servo exactly 10°.
2. The servo holds its position between presses.
3. After 18 presses (reaching 180°), the next press resets the servo to 0°.
4. No unintended movement occurs when the button is not pressed.

All conditions were satisfied. The servo responded smoothly and consistently, with no jitter between presses — confirming that the PWM signal and edge-detection logic are working correctly.

Demo Video

The video below shows the servo rotating 10° with each button press.