What Is the Raspberry Pi Pico? MicroPython Setup, Pinout and First Projects

The Raspberry Pi Pico is a very cheap, palm-sized microcontroller board built around the RP2040, a chip designed by the Raspberry Pi Foundation itself. Its standout feature is that it can be programmed in MicroPython, in other words in Python: you write your code, run it and see the result straight away, with no waiting for compilation. That makes it a great gateway for students learning Python and for electronics beginners. If you prefer, you can also program it in C/C++ or with the Arduino IDE.

What is the Raspberry Pi Pico? How it differs from a Raspberry Pi

Despite the similar name, the Pico is not a computer like the Raspberry Pi 4 or 5. It has no operating system, no HDMI output and no desktop; like an Arduino, it's a microcontroller board that runs a single program. Your program starts the moment you power it up, it uses very little energy, and it handles jobs such as reading sensors, lighting LEDs and driving motors in real time.

Specifications: Pico, Pico W and Pico 2

Pico pinout

The Pico has 40 pins in total along its two edges. Every one of the 26 GPIO pins from GP0 to GP28 can output PWM, and I2C, SPI and UART can be used on several alternative pins. Analog input is only available on GP26, GP27 and GP28. You can see the board's full pin map in the Pinout tool; the important power and special pins are:

Installing MicroPython (with Thonny)

1. Download and install Thonny from thonny.org.
2. Hold down the BOOTSEL button on the Pico while plugging the USB cable into your computer; the Pico shows up as a drive called RPI-RP2 (RP2350 on the Pico 2).
3. In the interpreter menu at the bottom right of Thonny, choose MicroPython (Raspberry Pi Pico), then use "Install or update MicroPython" to install the right version for your board (Pico, Pico W or Pico 2). You can also download the .uf2 file from micropython.org and drag it onto the drive.
4. When the installation finishes, the Pico restarts. If you see the >>> prompt in the Shell at the bottom of Thonny, you're ready.
5. If you save your code to the Pico as main.py, it runs automatically every time the board powers up, even when it's not connected to a computer.

First program: blinking the built-in LED

1from machine import Pin
2import time
3
4led = Pin(25, Pin.OUT)      # Pico'da dahili LED; Pico W ve Pico 2 W'de Pin("LED") yaz
5                            # onboard LED on Pico; use Pin("LED") on Pico W / Pico 2 W
6
7while True:
8    led.toggle()            # durumu tersine çevir / flip the state
9    time.sleep(0.5)

Controlling an LED with a button

Connect an LED to GP15 through a 220 Ω resistor and a button to GP14. The other leg of the button goes to GND, and the Pico's internal pull-up resistor is enabled, so the button reads 1 when released and 0 when pressed:

1from machine import Pin
2
3led = Pin(15, Pin.OUT)
4button = Pin(14, Pin.IN, Pin.PULL_UP)   # butonun diğer ucu GND'de / other leg to GND
5
6while True:
7    led.value(not button.value())        # basılıyken yanar / on while pressed

LED brightness with PWM

Every GPIO pin on the Pico can output PWM. In MicroPython the duty value ranges from 0 to 65535. The code below slowly brightens an LED and then starts again; you'll find the idea behind PWM explained in detail in What Is PWM?

1from machine import Pin, PWM
2import time
3
4led = PWM(Pin(15), freq=1000)
5
6while True:
7    for d in range(0, 65536, 1024):   # yavaşça yan / fade in
8        led.duty_u16(d)
9        time.sleep_ms(10)

Analog readings and the built-in temperature sensor

Connect a potentiometer's middle pin to GP26 and its outer pins to 3V3 and GND. read_u16() returns a value from 0 to 65535. The Pico also has a temperature sensor inside, connected to the ADC's 4th channel; it's only a rough reading, but it's a fun way to measure temperature without any extra parts:

1from machine import ADC
2import time
3
4pot = ADC(26)                    # GP26 (ADC0) / potansiyometre orta ucu / pot wiper
5sensor = ADC(4)                  # dahili sıcaklık sensörü / internal temperature sensor
6
7while True:
8    value = pot.read_u16()                       # 0–65535
9    volts = sensor.read_u16() * 3.3 / 65535
10    temp = 27 - (volts - 0.706) / 0.001721       # °C (yaklaşık / approximate)
11    print(value, round(temp, 1))
12    time.sleep(1)

Programming the Pico with the Arduino IDE

If you prefer C++ and Arduino libraries, you can also use the Pico with the Arduino IDE. Add https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json to the additional boards URLs field in File > Preferences, then install Earle Philhower's Raspberry Pi Pico/RP2040/RP2350 package from the Boards Manager. For the first upload, hold the BOOTSEL button while connecting the board; after that, uploads work normally. The Blink example with LED_BUILTIN and most Arduino libraries work without trouble.

Pico, ESP32 or Arduino?

For projects that need wireless, get to know the ESP32 in What Is the ESP32? A strength unique to the Pico is its PIO (programmable input/output) blocks: they handle timing-critical jobs such as WS2812B LED strips or custom communication protocols without burdening the processor.

Raspberry Pi Pico project ideas

• Traffic light: a traffic light with three LEDs lighting in sequence.
• Knight Rider: a light effect running back and forth across six LEDs.
• Buttons and interrupts (IRQ): code that catches a button press without waiting for the main loop.
• RGB colour cycle: a rainbow effect on an RGB LED with three PWM channels.
• Pico W web server: control an LED or relay from a page opened on your phone.
• Mini thermometer: show the built-in temperature sensor's reading on an OLED display.

Common mistakes and how to fix them

• The RPI-RP2 drive doesn't appear: the board was plugged in without holding BOOTSEL, or the cable is charge-only; use a data cable.
• Thonny can't find the board: the wrong interpreter is selected, or MicroPython isn't installed on the board.
• The LED doesn't light on a Pico W: on the Pico W the built-in LED is connected to the wireless chip; use Pin("LED") instead of Pin(25).
• Connecting 5 V signals: the GPIOs are 3.3 V; 5 V signals can damage a pin.
• The code doesn't run when unplugged from the computer: it wasn't saved to the Pico as main.py.
• Too much voltage on VSYS: VSYS accepts at most 5.5 V; don't connect a 9 V or 12 V adapter directly.

With its low price and Python support, the Raspberry Pi Pico is one of the easiest ways to bring coding and electronics together. You'll find LED basics in What Is an LED?; in the BlueGrays app you'll find Pico projects for blinking LEDs, a traffic light, Knight Rider, button interrupts, a PWM breathing effect and an RGB colour cycle, step by step with circuit diagrams and MicroPython code.