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Session 2: Setting Up the Development Workflow

Synopsis

Introduces firmware installation, serial access, file transfer, REPL usage, and common development tools for editing, running, and testing MicroPython code on the Pico 2 W.

Session Content

Session 2: Setting Up the Development Workflow

Session Duration

  • 45 minutes

Session Overview

In this session, learners set up a practical MicroPython development workflow for the Raspberry Pi Pico 2 W. The focus is on preparing the board, connecting Thonny, uploading code, using the REPL, saving scripts to the device, and validating the setup with simple hardware and software tests.

Learning Objectives

By the end of this session, learners will be able to:

  • Prepare a Raspberry Pi Pico 2 W for MicroPython development
  • Install and configure Thonny for Pico development
  • Connect to the Pico 2 W REPL using USB
  • Upload and run MicroPython scripts on the board
  • Save a startup script as main.py
  • Use basic debugging techniques in Thonny
  • Verify the workflow with a simple LED blink program

Prerequisites

  • A Raspberry Pi Pico 2 W
  • USB cable with data support
  • A computer with internet access
  • Thonny IDE installed
  • Micro-USB or USB-C adapter as required by the host computer
  • Optional: external LED, resistor, breadboard, and jumper wires

Session Agenda

1. Introduction to the Development Workflow (5 minutes)

  • What MicroPython is
  • Why Pico development is different from standard desktop Python
  • Overview of the workflow:
  • Write code in Thonny
  • Send code to Pico
  • Run code on device
  • View output in REPL
  • Save persistent scripts to main.py

2. Installing and Configuring Thonny (10 minutes)

  • Install Thonny
  • Select the correct MicroPython interpreter
  • Connect to the Raspberry Pi Pico 2 W
  • Confirm the board is visible in the IDE

3. First Connection and REPL Usage (10 minutes)

  • Open the REPL
  • Run a simple command
  • Read board information
  • Use Ctrl+C to interrupt running code
  • Reset the device if needed

4. Save and Run a Script on the Pico (10 minutes)

  • Create a Python file in Thonny
  • Upload it to the board
  • Run it manually
  • Save it as main.py so it runs on boot
  • Blink the onboard LED
  • Introduce simple error handling and output printing
  • Verify code behavior through the REPL

Development Environment Setup

Install Thonny

  1. Download and install Thonny from the official website.
  2. Launch Thonny.
  3. Go to Tools > Options > Interpreter.
  4. Select:
  5. MicroPython (Raspberry Pi Pico)
  6. Connect the Pico 2 W via USB.
  7. If prompted, choose the correct port.

Confirm MicroPython Firmware

If the board is new or not running MicroPython: 1. Hold the BOOTSEL button while connecting the Pico to USB. 2. The board appears as a USB mass storage device. 3. Copy the MicroPython .uf2 firmware to the board. 4. The Pico reboots after flashing.

Verify Connection

In Thonny, the shell should show a prompt like:

MicroPython v1.x.x on 202x-xx-xx; Raspberry Pi Pico W with RP2040
Type "help()" for more information.
>>>

Theory: Understanding the Workflow

MicroPython on Pico 2 W

MicroPython is a lightweight Python implementation designed for microcontrollers. On the Pico 2 W, it allows you to: - Control GPIO pins - Read sensors - Drive actuators - Connect to Wi-Fi - Build small IoT devices

Thonny as a Development Tool

Thonny is beginner-friendly and supports: - Code editing - Running code on the device - REPL interaction - File transfer to/from the Pico - Debugging with simple variable inspection

REPL Basics

REPL stands for Read-Eval-Print Loop. It lets you: - Run commands one line at a time - Inspect variables - Test small code snippets quickly

Example:

print("Hello from Pico 2 W!")

Expected output:

Hello from Pico 2 W!

Hands-On Exercise 1: Verify the REPL

Goal

Confirm the Pico is connected and responding to MicroPython commands.

Steps

  1. Open Thonny.
  2. Connect to the Pico 2 W interpreter.
  3. In the Shell, type:
import machine
print(machine.freq())

Expected Output

150000000

This value indicates the CPU clock speed in Hz.

Additional Test

Try:

import sys
print(sys.platform)

Expected output:

rp2

Goal

Create a simple script that blinks the onboard LED on the Pico 2 W.

Notes

The onboard LED can usually be accessed using machine.Pin("LED") on Pico boards that support it.

Code

from machine import Pin
from time import sleep

# Create an output pin for the onboard LED
led = Pin("LED", Pin.OUT)

# Blink the LED forever
while True:
    led.toggle()
    print("LED toggled")
    sleep(0.5)

What This Teaches

  • Importing modules
  • Configuring GPIO
  • Using an infinite loop
  • Adding diagnostic output
  • Timing with sleep()

Expected Output

LED toggled
LED toggled
LED toggled
...

Hands-On Exercise 3: Save a Startup Script

Goal

Make the Pico run a script automatically after reboot.

Steps

  1. Open a new file in Thonny.
  2. Paste the blink script.
  3. Save it to the Pico as main.py.
  4. Press the reset button or disconnect/reconnect USB.

Result

The script starts automatically when the Pico powers on or resets.

Example main.py

from machine import Pin
from time import sleep

# Set up the onboard LED
led = Pin("LED", Pin.OUT)

# Main loop
while True:
    led.on()
    print("LED ON")
    sleep(1)

    led.off()
    print("LED OFF")
    sleep(1)

Expected Output

LED ON
LED OFF
LED ON
LED OFF
...

Debugging Techniques

1. Use Print Statements

Add print() calls to show program flow.

Example:

print("Starting program...")

2. Interrupt a Running Program

  • Press Ctrl+C in the Thonny Shell to stop a loop.

3. Reset the Board

  • Use the reset button if available
  • Or disconnect and reconnect USB

4. Check Common Errors

  • Wrong interpreter selected
  • USB cable without data wires
  • Script saved to the computer instead of the Pico
  • Syntax errors from missing colons or indentation

Mini Challenge

Modify the blink script so that: - The LED turns on for 200 ms - Turns off for 800 ms - Prints "blink cycle complete" after each cycle

Starter Code

from machine import Pin
from time import sleep

led = Pin("LED", Pin.OUT)

while True:
    led.on()
    sleep(0.2)
    led.off()
    sleep(0.8)
    print("blink cycle complete")

Expected Output

blink cycle complete
blink cycle complete
blink cycle complete
...

Knowledge Check

  1. What is the REPL used for?
  2. How do you connect Thonny to the Pico 2 W?
  3. What file name should be used for code that runs at boot?
  4. How can you stop a running infinite loop?
  5. Why is print() useful during development?

Session Summary

In this session, learners: - Installed and configured Thonny - Connected to the Pico 2 W MicroPython REPL - Uploaded and ran scripts on the board - Saved code as main.py - Tested GPIO control with the onboard LED - Practiced basic debugging and workflow validation

  • Repeat the blink example from memory
  • Change the blink interval
  • Add extra print() statements to trace execution
  • Experiment with Pin("LED").on() and .off() in the REPL
  • Save a custom startup script and reboot the Pico

Reference Code Snippets

Quick REPL Test

print("Pico 2 W is connected")

LED Control in REPL

from machine import Pin
led = Pin("LED", Pin.OUT)
led.on()
led.off()

Show Platform Information

import sys
print(sys.platform)

Suggested Equipment for the Next Session

  • Raspberry Pi Pico 2 W
  • Breadboard
  • 1 LED
  • 1 220Ω resistor
  • Jumper wires
  • USB cable
  • Thonny IDE

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