Xiao RP2040 Arduino-Pico

PinoutPinoutInstalling via Arduino Boards Manager

Ref. Installation

1. Open up the Arduino IDE and go to File->Preferences.
2. In the dialog that pops up, enter the following URL in the “Additional Boards Manager URLs” https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json
3. Hit OK to close the dialog.
4. Go to Tools->Boards->Board Manager in the IDE
5. Type “pico” in the search box and select “Add”:

Blink

26 (Work)GP26 (Error)P26 (Error)D0 (Work)26 and D1 (Work)0 (other pin:P0/TX/D6 Work)

///
/// Work
///
const int ledPin = 26;  // Pin where the LED is connected P26/A0/D0

void setup() {
  pinMode(ledPin, OUTPUT);  // Set the LED pin as an output
}

void loop() {
  digitalWrite(ledPin, HIGH);  // Turn the LED on
  delay(1000);                 // Wait for 1 second
  digitalWrite(ledPin, LOW);   // Turn the LED off
  delay(1000);                 // Wait for 1 second
}

///
/// Error
///
const int ledPin = GP26;  // Pin where the LED is connected P26/A0/D0

void setup() {
  pinMode(ledPin, OUTPUT);  // Set the LED pin as an output
}

void loop() {
  digitalWrite(ledPin, HIGH);  // Turn the LED on
  delay(1000);                 // Wait for 1 second
  digitalWrite(ledPin, LOW);   // Turn the LED off
  delay(1000);                 // Wait for 1 second
}

///
/// Error
///
const int ledPin = P26;  // Pin where the LED is connected P26/A0/D0

void setup() {
  pinMode(ledPin, OUTPUT);  // Set the LED pin as an output
}

void loop() {
  digitalWrite(ledPin, HIGH);  // Turn the LED on
  delay(1000);                 // Wait for 1 second
  digitalWrite(ledPin, LOW);   // Turn the LED off
  delay(1000);                 // Wait for 1 second
}

///
/// Work
///
const int ledPin = D0;  // Pin where the LED is connected P26/A0/D0

void setup() {
  pinMode(ledPin, OUTPUT);  // Set the LED pin as an output
}

void loop() {
  digitalWrite(ledPin, HIGH);  // Turn the LED on
  delay(1000);                 // Wait for 1 second
  digitalWrite(ledPin, LOW);   // Turn the LED off
  delay(1000);                 // Wait for 1 second
}

///
/// Work
///
const int ledPin1 = 26;  // Pin where the LED is connected P26/A0/D0
const int ledPin2 = D1;  // Pin where the LED is connected P27/A1/D1

void setup() {
  pinMode(ledPin1, OUTPUT);  // Set the LED pin as an output
  pinMode(ledPin2, OUTPUT);  // Set the LED pin as an output
}

void loop() {
  digitalWrite(ledPin1, HIGH);  // Turn the LED on
  digitalWrite(ledPin2, HIGH);  // Turn the LED on
  delay(1000);                 // Wait for 1 second
  digitalWrite(ledPin1, LOW);   // Wait for 1 second
  digitalWrite(ledPin2, LOW);   // Wait for 1 second
  delay(1000);                 // Wait for 1 second
}

///
/// Work
///
const int ledPin = 0;  // Pin where the LED is connected P0/TX/D6

void setup() {
  pinMode(ledPin, OUTPUT);  // Set the LED pin as an output
}

void loop() {
  digitalWrite(ledPin, HIGH);  // Turn the LED on
  delay(1000);                 // Wait for 1 second
  digitalWrite(ledPin, LOW);   // Turn the LED off
  delay(1000);                 // Wait for 1 second
}

DAC(D/A Converter): Analog Output

DAC (Digital-to-Analog Converter)

Xiao RP2040 doesn’t have a hardware DAC, so analogWrite() generates a PWM-based simulated analog signal.

analogWright()

analogWrite() generates a PWM signal that mimics an analog output on microcontrollers without a DAC (e.g., RP2040).
analogWrite() outputs a true analog voltage on microcontrollers with a DAC (e.g., ESP32)

analogWrite() works only on PWM-supported pins in Arduino. However, Xiao RP2040 can use PWM on any digital pin, so analogWrite() works on all pins on this board.

26(Work)A0(Work)D0(Work)D4(Work in Any PWM Pin)

///
///Work
///
int ledPin = 26;  // LED connected to pin P26/A0/D0

void setup() {
  // nothing happens in setup
}

void loop() {
  // fade in from min to max in increments of 5 points:
  for (int fadeValue = 0; fadeValue <= 255; fadeValue += 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }

  // fade out from max to min in increments of 5 points:
  for (int fadeValue = 255; fadeValue >= 0; fadeValue -= 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }
}

///
///Work
///
int ledPin = A0;  // LED connected to pin P26/A0/D0

void setup() {
  // nothing happens in setup
}

void loop() {
  // fade in from min to max in increments of 5 points:
  for (int fadeValue = 0; fadeValue <= 255; fadeValue += 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }

  // fade out from max to min in increments of 5 points:
  for (int fadeValue = 255; fadeValue >= 0; fadeValue -= 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }
}

///
///Work
///
int ledPin = D0;  // LED connected to pin P26/A0/D0

void setup() {
  // nothing happens in setup
}

void loop() {
  // fade in from min to max in increments of 5 points:
  for (int fadeValue = 0; fadeValue <= 255; fadeValue += 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }

  // fade out from max to min in increments of 5 points:
  for (int fadeValue = 255; fadeValue >= 0; fadeValue -= 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }
}

///
///Work
///
int ledPin = D4;  // LED connected to pin P6/SDA/D4

void setup() {
  // nothing happens in setup
}

void loop() {
  // fade in from min to max in increments of 5 points:
  for (int fadeValue = 0; fadeValue <= 255; fadeValue += 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }

  // fade out from max to min in increments of 5 points:
  for (int fadeValue = 255; fadeValue >= 0; fadeValue -= 5) {
    // sets the value (range from 0 to 255):
    analogWrite(ledPin, fadeValue);
    // wait for 30 milliseconds to see the dimming effect
    delay(30);
  }
}

ADC(A/D Converter): Analog Input

ADC (Analog-to-Digital Converter)

Xiao RP2040’s A0, A1, A2, and A3 are pins that support Analog Input.

10bit A012bit A012bit 2612bit D0

///
///Work
///
/// Connect A0 to GND, Serial Monitor shows value = 0
/// Connect A0 to 3.3V, Serial Monitor shows value = 1023
///
int analogPin = A0;  //  Pin where the analogRead is connected P26/A0/D0

void setup() {
    Serial.begin(115200);  // Start serial communication at 115200 baud rate

}

void loop() {
    int sensorValue = analogRead(analogPin);  // Reads the voltage from pin A0 (0V to 3.3V) and converts it into a 12-bit value (0-4095)

    Serial.println(sensorValue);  // Print the value to the Serial Monitor
    delay(500);  // Wait 500 milliseconds before the next reading
}

///
///Work
///
/// Connect A0 to GND, Serial Monitor shows value = 0
/// Connect A0 to 3.3V, Serial Monitor shows value = 4095
///
int analogPin = A0;  //  Pin where the analogRead is connected P26/A0/D0

void setup() {
    Serial.begin(115200);  // Start serial communication at 115200 baud rate
    analogReadResolution(12);  // Set ADC resolution to 12-bit (0-4095)
}

void loop() {
    int sensorValue = analogRead(analogPin);  // Reads the voltage from pin A0 (0V to 3.3V) and converts it into a 12-bit value (0-4095)

    Serial.println(sensorValue);  // Print the value to the Serial Monitor
    delay(500);  // Wait 500 milliseconds before the next reading
}

///
///Work
///
/// Connect A0 to GND, Serial Monitor shows value = 0
/// Connect A0 to 3.3V, Serial Monitor shows value = 4095
///
int analogPin = 26;  //  Pin where the analogRead is connected P26/A0/D0

void setup() {
    Serial.begin(115200);  // Start serial communication at 115200 baud rate
    analogReadResolution(12);  // Set ADC resolution to 12-bit (0-4095)
}

void loop() {
    int sensorValue = analogRead(analogPin);  // Reads the voltage from pin A0 (0V to 3.3V) and converts it into a 12-bit value (0-4095)

    Serial.println(sensorValue);  // Print the value to the Serial Monitor
    delay(500);  // Wait 500 milliseconds before the next reading
}

///
///Work
///
/// Connect A0 to GND, Serial Monitor shows value = 0
/// Connect A0 to 3.3V, Serial Monitor shows value = 4095
///
int analogPin = D0;  //  Pin where the analogRead is connected P26/A0/D0

void setup() {
    Serial.begin(115200);  // Start serial communication at 115200 baud rate
    analogReadResolution(12);  // Set ADC resolution to 12-bit (0-4095)
}

void loop() {
    int sensorValue = analogRead(analogPin);  // Reads the voltage from pin A0 (0V to 3.3V) and converts it into a 12-bit value (0-4095)

    Serial.println(sensorValue);  // Print the value to the Serial Monitor
    delay(500);  // Wait 500 milliseconds before the next reading
}

The D0 pin is a digital pin, but it can also be used as an analog input. However, it may have lower stability and accuracy compared to the A0 pin.

I2C Scanner

#include <Wire.h>

void setup() {
  Wire.begin();
  Serial.begin(9600);
  while (!Serial);  // wait for serial monitor
  Serial.println("\nI2C Scanner");
}

void loop() {
  byte error, address;
  int nDevices;

  Serial.println("Scanning...");

  nDevices = 0;
  for (address = 1; address < 127; address++) {
    // The i2c_scanner uses the return value of
    // the Write.endTransmisstion to see if
    // a device did acknowledge to the address.
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0) {
      Serial.print("I2C device found at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.print(address, HEX);
      Serial.println("  !");

      nDevices++;
    } else if (error == 4) {
      Serial.print("Unknown error at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.println(address, HEX);
    }
  }
  if (nDevices == 0)
    Serial.println("No I2C devices found\n");
  else
    Serial.println("done\n");

  delay(5000);  // wait 5 seconds for next scan
}

When the port suddenly stops being recognized in Arduino IDE

Simple way More detailed way

1. Download Blink.ino.uf2
2. Press Boot Button of Xiao and connect to PC
3. Drag uf2 file to RPI-RP2 drive
   
4. After the Blink code run, the port will be recognized

1. Open an example code such as Blink
   or Copy below

   // Blink
   void setup() {
     pinMode(LED_BUILTIN, OUTPUT);
   }
   void loop() {
     digitalWrite(LED_BUILTIN, HIGH);
     delay(1000);
     digitalWrite(LED_BUILTIN, LOW);
     delay(1000);
   }
   

2. Compile the code
3. Find the path to Blink.ino.uf2
4. Open terminal and open the folder

   % pwd
   /Users/yuichi
   % cd /Users/yuichi/Library/Caches/arduino/sketches/967F6001D67A7E915EC42BA164079EB8
   % open .
   

5. Press Boot Button of Xiao and connect to PC
6. Drag uf2 file to RPI-RP2 drive

7. After the Blink code run, the port will be recognized