Micropython Repl

MicroPython REPL and Package Management

Master the MicroPython REPL (Read-Eval-Print Loop) for interactive development, package management, and quick testing on the Universe 2025 (Tufty) Badge.

Connecting to REPL

Using screen (macOS/Linux)

# Find the device
ls /dev/tty.usb*

# Connect (115200 baud)
screen /dev/tty.usbmodem* 115200

# Exit screen: Ctrl+A then K, then Y to confirm

Using mpremote

# Install mpremote
pip install mpremote

# Connect to REPL
mpremote connect /dev/tty.usbmodem*

# Or auto-detect
mpremote

Using Thonny IDE

1. Open Thonny
2. Tools → Options → Interpreter
3. Select "MicroPython (RP2040)"
4. Choose correct port
5. Shell window shows REPL

REPL Basics

Special Commands

# Ctrl+C - Interrupt running program
# Ctrl+D - Soft reboot
# Ctrl+E - Enter paste mode (for multi-line code)
# Ctrl+B - Exit paste mode and execute

# Help system
help()              # General help
help(modules)       # List all modules
help(badgeware)     # Help on specific module

# Quick info
import sys
sys.implementation  # MicroPython version
sys.platform        # Platform info

Interactive Testing

# Test code immediately
>>> from badgeware import screen, display, brushes
>>> screen.brush = brushes.color(255, 255, 255)
>>> screen.text("Test", 10, 10, 2)
>>> display.update()

# Test calculations
>>> temp = 23.5
>>> temp_f = temp * 9/5 + 32
>>> print(f"{temp}C = {temp_f}F")

# Test GPIO
>>> from machine import Pin
>>> led = Pin(25, Pin.OUT)
>>> led.toggle()  # Toggle LED immediately

Paste Mode for Multi-line Code

# Enter paste mode: Ctrl+E
# Paste your code:
def calculate_distance(x1, y1, x2, y2):
    import math
    dx = x2 - x1
    dy = y2 - y1
    return math.sqrt(dx*dx + dy*dy)

print(calculate_distance(0, 0, 3, 4))
# Exit paste mode: Ctrl+D

Package Management

Using mip (MicroPython Package Installer)

# Install package from micropython-lib
import mip
mip.install("urequests")        # HTTP client
mip.install("logging")           # Logging module
mip.install("umqtt.simple")      # MQTT client

# Install from GitHub
mip.install("github:org/repo/package.py")

# Install to specific location
mip.install("urequests", target="/lib")

Using upip (older method)

# Connect to WiFi first
import network
wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect('SSID', 'password')

# Wait for connection
while not wlan.isconnected():
    pass

# Install package
import upip
upip.install("micropython-logging")
upip.install("picoweb")

Manual Package Installation

# From your computer, copy files to badge
mpremote cp mymodule.py :/lib/mymodule.py

# Or using ampy
ampy --port /dev/tty.usbmodem* put mymodule.py /lib/mymodule.py

# Then use in REPL
>>> import mymodule

Module Inspection

List Available Modules

# List all built-in and installed modules
help('modules')

# Check if module exists
import sys
'badgeware' in sys.modules  # False until imported

import badgeware
'badgeware' in sys.modules  # True after import

Inspect Module Contents

# See what's in a module
import badgeware
dir(badgeware)  # List all attributes

# Check specific attributes
hasattr(badgeware, 'screen')  # True
hasattr(badgeware, 'brushes')  # True

# Get function signature
help(badgeware.screen)

# Explore submodules
from badgeware import shapes
dir(shapes)  # See all shape functions

# View source (if available)
import inspect
inspect.getsource(mymodule.myfunction)  # May not work on compiled modules

Check Module Location

# Find where module is located
import badgeware
badgeware.__file__  # Shows file path

# List files in system directory
import os
os.listdir('/system')
os.listdir('/system/apps')  # MonaOS apps

Interactive Debugging

Quick Variable Inspection

# Run code and inspect
>>> x = [1, 2, 3, 4, 5]
>>> len(x)
5
>>> type(x)
<class 'list'>
>>> sum(x)
15

# Object inspection
>>> import badgeware
>>> type(badgeware.screen)
<class 'Screen'>
>>> dir(badgeware.screen)  # See all methods
>>> dir(badgeware.brushes)  # See brush functions
>>> dir(badgeware.shapes)  # See shape functions

Print Debugging

# Test function with prints
def process_data(data):
    print(f"Input: {data}")
    result = data * 2
    print(f"Result: {result}")
    return result

>>> process_data(5)
Input: 5
Result: 10
10

Exception Handling

# Test error handling
>>> try:
...     1 / 0
... except ZeroDivisionError as e:
...     print(f"Error: {e}")
Error: division by zero

# Get full traceback
import sys
try:
    buggy_function()
except Exception as e:
    sys.print_exception(e)

Memory Debugging

# Check memory usage
import gc
gc.collect()  # Run garbage collection
gc.mem_free()  # Free memory in bytes
gc.mem_alloc()  # Allocated memory

# Monitor memory during operation
before = gc.mem_free()
# ... do something
after = gc.mem_free()
print(f"Memory used: {before - after} bytes")

Useful REPL Helpers

Create a helpers.py file

# helpers.py - Load in REPL for common tasks
import gc
import sys
import os
from machine import Pin, freq

def info():
    """Display system information"""
    print(f"Platform: {sys.platform}")
    print(f"Version: {sys.version}")
    print(f"CPU Frequency: {freq()} Hz")
    print(f"Free Memory: {gc.mem_free()} bytes")

def ls(path='/'):
    """List files in directory"""
    try:
        files = os.listdir(path)
        for f in files:
            print(f)
    except:
        print(f"Error listing {path}")

def cat(filename):
    """Display file contents"""
    try:
        with open(filename, 'r') as f:
            print(f.read())
    except Exception as e:
        print(f"Error: {e}")

def rm(filename):
    """Remove file"""
    try:
        os.remove(filename)
        print(f"Removed {filename}")
    except Exception as e:
        print(f"Error: {e}")

def blink(pin=25, times=3):
    """Blink LED for testing"""
    import time
    led = Pin(pin, Pin.OUT)
    for i in range(times):
        led.toggle()
        time.sleep(0.5)
    led.value(0)

# Load in REPL with:
# >>> from helpers import *
# >>> info()

Auto-run at REPL start

Create boot.py to run code on startup:

# boot.py - Runs on every boot
import gc
gc.collect()

# Optional: Auto-import common modules
# from badgeware import screen, display, brushes, shapes
# import time

print("Universe 2025 Badge Ready!")
print(f"Free memory: {gc.mem_free()} bytes")

Quick Testing Workflows

Test Hardware Function

# Test I2C scan
from machine import I2C, Pin
i2c = I2C(0, scl=Pin(5), sda=Pin(4), freq=400000)
devices = i2c.scan()
print(f"Found devices: {[hex(d) for d in devices]}")

# Test display
from badgeware import screen, display, brushes
screen.brush = brushes.color(0, 0, 0)
screen.clear()
screen.brush = brushes.color(255, 255, 255)
screen.text("REPL Test", 10, 10, 2)
display.update()

Test Network Connection

import network
import time

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
print("Connecting to WiFi...")
wlan.connect('YOUR_SSID', 'YOUR_PASSWORD')

timeout = 10
while not wlan.isconnected() and timeout > 0:
    print(".", end="")
    time.sleep(1)
    timeout -= 1

if wlan.isconnected():
    print("\nConnected!")
    print(f"IP: {wlan.ifconfig()[0]}")
else:
    print("\nConnection failed")

Test API Call

import urequests
import json

response = urequests.get('https://api.github.com/zen')
print(response.text)
response.close()

# JSON API
response = urequests.get('https://api.example.com/data')
data = response.json()
print(data)
response.close()

File System Operations

List and Navigate Files

import os

# Current directory
os.getcwd()

# List files
os.listdir()
os.listdir('/lib')

# File info
os.stat('main.py')  # Returns (mode, ino, dev, nlink, uid, gid, size, atime, mtime, ctime)

# Check if file exists
try:
    os.stat('main.py')
    print("File exists")
except:
    print("File not found")

Read/Write Files

# Write file
with open('test.txt', 'w') as f:
    f.write('Hello from REPL!\n')

# Read file
with open('test.txt', 'r') as f:
    content = f.read()
    print(content)

# Append to file
with open('log.txt', 'a') as f:
    f.write(f'Log entry: {time.time()}\n')

Remove Files

import os

# Remove file
os.remove('test.txt')

# Remove directory (must be empty)
os.rmdir('mydir')

Checking Installed Packages

Verify Package Installation

# Method 1: Try to import
try:
    import urequests
    print("urequests is installed")
    print(f"Location: {urequests.__file__}")
except ImportError:
    print("urequests not installed")

# Method 2: Check file system
import os
lib_files = os.listdir('/lib')
print("Installed in /lib:")
for f in lib_files:
    print(f"  {f}")

# Method 3: Check sys.path
import sys
print("Module search paths:")
for path in sys.path:
    print(f"  {path}")

Package Version Info

# Some packages have __version__
import urequests
if hasattr(urequests, '__version__'):
    print(f"urequests version: {urequests.__version__}")

# Check MicroPython version
import sys
print(sys.version)
print(sys.implementation)

REPL Tips and Tricks

History Navigation

• Up/Down arrows: Navigate command history
• Tab: Auto-completion (limited support)

Copy Output from REPL

# Run command and capture output
>>> result = []
>>> for i in range(10):
...     result.append(i * 2)
>>> print(result)
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]

# Copy from terminal window

Run Script from REPL

# Import and run
import myapp
myapp.main()

# Or reload after changes
import sys
if 'myapp' in sys.modules:
    del sys.modules['myapp']
import myapp

Timing Code

import time

start = time.ticks_ms()
# ... your code here
for i in range(1000):
    x = i * 2
end = time.ticks_ms()

print(f"Execution time: {time.ticks_diff(end, start)}ms")

Common REPL Issues

REPL not responding: Press Ctrl+C to interrupt, or Ctrl+D to soft reset

Can't import module: Check sys.path, verify file is in /lib or root directory

Out of memory: Run gc.collect(), reduce variable usage, delete large objects

Module changes not reflected: Delete from sys.modules and re-import

Connection lost: Reconnect with screen or mpremote, check USB cable

Using mpremote for Quick Operations

# Execute Python code remotely
mpremote exec "import machine; print(machine.freq())"

# Run local script on device
mpremote run test.py

# Copy file to device
mpremote cp test.py :main.py

# Copy file from device
mpremote cp :main.py local.py

# Mount local directory on device
mpremote mount .

# Filesystem operations
mpremote ls
mpremote mkdir /data
mpremote rm test.txt

# Chain commands
mpremote connect /dev/tty.usbmodem* cp main.py :main.py exec "import main"

REPL Best Practices

1. Save work frequently - REPL state is lost on reboot
2. Use paste mode for multi-line code
3. Run gc.collect() before memory-intensive operations
4. Test incrementally - Build up complex code piece by piece
5. Create helper functions in a dedicated module
6. Use print() liberally for debugging
7. Soft reset (Ctrl+D) to clear state between tests
8. Keep REPL sessions short - Move working code to files

Integration with Development Workflow

1. Prototype in REPL - Test ideas interactively
2. Save to file - Once code works, save to .py file
3. Test from file - Import and run from REPL
4. Iterate - Make changes, reload, test
5. Deploy - Upload final version to badge

The REPL is your best friend for rapid experimentation and debugging on the Badger 2350!