Documentation

// Seeeduino XIAO SAMD21 - Built-in LED blink
// Install: Boards Manager -> "Seeed SAMD Boards" by Seeed Studio
// Select Board: "Seeeduino XIAO"

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

void loop() {
  digitalWrite(LED_BUILTIN, LOW);   // LED is active LOW
  delay(500);
  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
}

// Seeeduino XIAO SAMD21 - Generate a sine wave on the DAC (D0 / A0)
// The SAMD21 has a true 10-bit DAC (0-1023 maps to 0-3.3V)

#include <math.h>

const int dacPin = A0;   // D0 / A0 is the DAC output
const int samples = 100;
int wave[samples];

void setup() {
  analogWriteResolution(10);   // 10-bit DAC
  for (int i = 0; i < samples; i++) {
    wave[i] = int(512.0 + 511.0 * sin(2.0 * M_PI * i / samples));
  }
}

void loop() {
  for (int i = 0; i < samples; i++) {
    analogWrite(dacPin, wave[i]);
    delayMicroseconds(50);
  }
}

// Seeeduino XIAO SAMD21 - Send keystrokes over native USB HID
// Wire a button between D3 and GND

#include <Keyboard.h>

const int buttonPin = 3;   // D3
bool lastState = HIGH;

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  Keyboard.begin();
}

void loop() {
  bool state = digitalRead(buttonPin);
  if (state == LOW && lastState == HIGH) {
    Keyboard.print("Hello from XIAO!");
    Keyboard.write(KEY_RETURN);
    delay(50);   // simple debounce
  }
  lastState = state;
}

# Seeeduino XIAO SAMD21 - Capacitive touch on A0
# Drop CircuitPython for "Seeed XIAO" onto the board, then save this as code.py

import board
import touchio
import time

touch = touchio.TouchIn(board.A0)

while True:
    if touch.value:
        print("Touched! raw =", touch.raw_value)
    else:
        print("idle    raw =", touch.raw_value)
    time.sleep(0.1)