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. Each button press increments the servo angle by 10°, resetting to 0° after 180°. Structured Serial.println() logging traces every cycle for verification.

#include <ESP32Servo.h>

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

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

void setup() {
  Serial.begin(115200);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  myServo.attach(SERVO_PIN);
  myServo.write(currentAngle);
}

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

  if (buttonState == LOW && lastButtonState == HIGH) {
    delay(50); // debounce
    if (digitalRead(BUTTON_PIN) == LOW) {
      cycleCount++;
      currentAngle += 10;
      if (currentAngle > 180) currentAngle = 0;

      Serial.print("[CYCLE "); Serial.print(cycleCount);
      Serial.println("] Button State: PRESSED (D1 = LOW)");
      Serial.print("[ACTION] Servo moving to ");
      Serial.print(currentAngle); Serial.println("°");
      myServo.write(currentAngle);
      Serial.print("[STATUS] Button PRESSED --> Servo at ");
      Serial.print(currentAngle); Serial.println("°");
      Serial.println("[INFO]   Waiting for next press...");
      Serial.println();
    }
  }

  lastButtonState = buttonState;
  delay(10);
}

Serial Monitor Output

Opening the Serial Monitor at 115200 baud shows each press cycle with its angle update. The output below captures two consecutive presses:

Each cycle takes ~2 seconds between presses (27.939 → 29.987), confirming clean edge detection with no phantom triggers between presses.

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.