Step 2: Put the Pico in Bootloader Mode

The Pico has exactly one button, marked BOOTSEL. It only matters at the moment of plugging in:

1. Make sure the Pico is unplugged.
2. Hold BOOTSEL down.
3. While still holding it, plug the USB cable into your computer.
4. Let go. A USB drive called RPI-RP2 appears.

That drive is the bootloader. Anything you copy onto it is written to flash, and the board reboots into it. There is no driver to install and no upload tool - the file manager is the flashing tool.

Step 3: Install MicroPython

The easiest route is to let Thonny do it:

1. In Thonny, click the interpreter selector in the bottom-right corner of the window.
2. Choose Install MicroPython….
3. Pick Raspberry Pi · Pico / Pico H as the variant, then Install.
4. When it finishes, the RPI-RP2 drive disappears - the board has rebooted into MicroPython.

The manual route works too: download the .uf2 file for the Pico from raspberrypi.com/documentation/microcontrollers/micropython.html and drag it onto the RPI-RP2 drive. Same result.

Step 4: Talk to the Board

At the bottom-right of Thonny, select MicroPython (Raspberry Pi Pico) as the interpreter. The Shell panel shows a >>> prompt. That prompt is running on the Pico - type into it and the chip responds:

The on-board LED is on GPIO 25. Being able to poke hardware one line at a time, with no compile and no upload, is the real advantage of MicroPython on this board - it is a far faster way to find out what a new sensor actually returns.

Step 5: Run a Real Program

Type this into the editor pane (the top half of the window):

1. Press the green Run button. The LED blinks. Press Stop to end it.
2. To make it survive a reboot: File → Save as… → Raspberry Pi Pico.
3. Name it exactly main.py.

The filename is the whole mechanism. MicroPython looks for a file called main.py on boot and runs it. Save it under any other name and it only runs when you press Run. Save it as main.py and the board does its job standalone from a phone charger, with no computer attached.

Step 6: An LED and a Button

Wire it up:

• GP15 (physical pin 20) → 330Ω resistor → LED anode
• LED cathode → GND (physical pin 23 or 38)
• Button between GP14 (pin 19) and GND

GP numbers are not pin numbers. The Pico has 40 physical pins and the GPIO labels do not line up with them - GP15 is physical pin 20. Keep a pinout diagram open; guessing costs more time than looking.

Step 7: Read the On-Chip Temperature Sensor

The RP2040 has a temperature sensor built into the silicon, on the fifth ADC channel. Nothing to wire:

Expect it to read a few degrees above room temperature - it measures the die, which is warmed by the chip itself. It is useful for spotting the board getting hot, not for reporting the weather.

Troubleshooting

• No RPI-RP2 drive: BOOTSEL was not held while plugging in, or the cable is charge-only. Unplug, hold the button down, plug in, then release.
• Thonny cannot connect / "port is busy": another program has the serial port open - a second Thonny window, or a serial monitor. Close it, then click Stop in Thonny to reconnect.
• A bad main.py locks the board out: press Stop in Thonny to interrupt it. If even that fails, hold BOOTSEL while plugging in and re-flash MicroPython - that wipes the filesystem and gives you a clean board back.
• Pin(25) does nothing: you have a Pico W. Its LED is wired to the wireless chip instead, so it is Pin("LED") there. See the Pico W tutorial.
• Readings jump around, or the board resets at random: an unsoldered Pico in a breadboard. Solder the headers.

Where to Go Next

• Move to the Pico W tutorial to put the same board on Wi-Fi.
• Drive a servo or a NeoPixel strip - MicroPython has a module for both built in.
• Try the PIO state machines, which are unique to the RP2040 and can bit-bang protocols without using a core.
• Compare with the Arduino Uno tutorial to see the same tasks in C++ on 5V hardware.