•

Cesar

Published July 30, 2025 © MIT

Analog Arm 2D

This project uses an joystick connected to a Dual MCU to control a 2D arm in Processing.

IntermediateProtip4 hours45

Things used in this project

Hardware components

Dual MCU

Analog joystick (Generic)

Software apps and online services

MicroPython

The Processing Foundation Processing

Story

What is this project about?

Analog Arm 2D is an interactive installation that lets you drive a two-segment robotic arm in Processing using a simple analog joystick. As you tilt the joystick, the arm’s joints rotate in real time and the window’s background color shifts smoothly based on the joystick’s X and Y positions.

Analog Arm 2D

Web Serial

https://analogarm2d.netlify.app/

What is this project about?

Why did we build it?

Visual feedbackIntegrating Processing to display live sensor data was both a creative challenge and an excellent way to gain hands-on experience with real-time graphics and color mapping.

Educational robotics demoWe want to inspire students and makers to see how a few lines of code and an inexpensive joystick can produce compelling, interactive graphics.

How does it work?

On the hardware side, the joystick’s X axis is wired to GPIO29 (ADC channel 3) and the Y axis to GPIO27 (ADC channel 1) on the Dual MCU (RP2040).
In main.py, we calibrate the joystick’s center point, scale raw ADC readings to the –50…+50 range, then stream comma-separated vx, vy pairs over USB serial at 115200 baud every 50 ms.

In the Processing sketch (arm.pde), we continuously read vx and vy, compute simple inverse-kinematics to calculate each joint angle, and redraw the arm. The background color is updated with:

background(
  map(vx, -50, 50, 0, 255),  // Red channel
  0,
  map(vy, -50, 50, 0, 255)   // Blue channel
);

Here’s a step-by-step guide to help you get started with the AnalogArm2D joystick-controlled web visualization using the Dual MCU board:

✅ Step 1: Wire Up Your Hardware

Connect X-axis of the joystick to GPIO29
Connect Y-axis to GPIO27
Power the DualMCU via USB

✅ Step 2: Upload main.py to the Dual MCU

Open Thonny IDE (or your preferred MicroPython editor).
Select Interpreter → MicroPython (Raspberry Pi Pico)
Create a new file and paste the provided MicroPython code (assumed you already have it).

Save it to the board:

File → Save As… → Raspberry Pi Pico → main.py

⏳ The board will automatically reboot and start sending scaled vx, vy values over the USB Serial port.

✅ Step 3: Launch the Web Interface

Open your browser and go to:
🔗 https://analogarm2d.netlify.app/

Click the “Connect Serial” button.
If prompted, select the COM port for the Dual MCU.

Once connected:

A 2-segment robotic arm will appear.
Move the joystick to control the arm and change the background color in real time.

If you’d like, I can also provide or review the MicroPython code that handles joystick input and serial output. Just let me know!

main.py

from machine import ADC
import time

# ADC pins: VX on GPIO29 (ADC3), VY on GPIO27 (ADC1)
adc_vx = ADC(3)  # GPIO29
adc_vy = ADC(1)  # GPIO27

def calibrar_joystick():
    suma_vx = 0
    suma_vy = 0
    muestras = 100
    for _ in range(muestras):
        suma_vx += adc_vx.read_u16()
        suma_vy += adc_vy.read_u16()
        time.sleep_ms(10)
    offset_vx = suma_vx // muestras
    offset_vy = suma_vy // muestras
    return offset_vx, offset_vy

def leer_joystick(offset_vx, offset_vy):
    vx = adc_vx.read_u16() - offset_vx
    vy = adc_vy.read_u16() - offset_vy
    return vx, vy

def escalar(valor, max_valor=30000, rango=50):
    valor = max(min(valor, max_valor), -max_valor)
    return round((valor / max_valor) * rango)

offset_vx, offset_vy = calibrar_joystick()
time.sleep(1)

while True:
    vx, vy = leer_joystick(offset_vx, offset_vy)
    vx_esc = escalar(vx)
    vy_esc = escalar(vy)
    print(f"{vx_esc},{vy_esc}")
    time.sleep(0.05)  # 50 ms → ~20 FPS

Credits

Fernando Flores

3 projects • 4 followers

Passionate about electronic engineering and microcontrollers, I love developing prototypes that complement my studies

Cesar

8 projects • 7 followers

💀 I am passionate about the technological world, specializing in the development of new technologies

Thanks to Alberto Villanueva and Adrián Rabadan.

Analog Arm 2D

Things used in this project

Hardware components

Software apps and online services

Story

What is this project about?

Web Serial

✅ Step 1: Wire Up Your Hardware

✅ Step 2: Upload main.py to the Dual MCU

✅ Step 3: Launch the Web Interface

Code

main.py

Credits

Fernando Flores

Cesar

Comments

Embed the widget on your own site

Analog Arm 2D

Analog Arm 2D

Things used in this project

Hardware components

Software apps and online services

Story

What is this project about?

Web Serial

✅ Step 1: Wire Up Your Hardware

✅ Step 2: Upload main.py to the Dual MCU

✅ Step 3: Launch the Web Interface

Code

main.py

Credits

Fernando Flores

Cesar

Comments

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