4-axis robot controller

KB2040 4-Axis Robot Arm Controller

USB controller for a 4-axis robot arm using an Adafruit KB2040 (RP2040). Four potentiometers for axis control plus a button for gripper/trigger — all read over a simple serial protocol.

BOM

PartQtyAdafruit KB2040110kΩ linear potentiometer4WWZMDiBTactile push button (momentary)1US-SKU E4293D-printed enclosure1USB-C cable1

Wiring

KB2040Connected toA0 (GP26)Pot 1 wiperA1 (GP27)Pot 2 wiperA2 (GP28)Pot 3 wiperA3 (GP29)Pot 4 wiperPin 9 (GP9)Button (other leg → 3.3V)3.3VPot 1–4 left legGNDPot 1–4 right leg, button pull-down

Potentiometer legs: left → 3.3V, right → GND, wiper (center) → analog pin.

Button is active-high (press sends 3.3V to GP9). The firmware uses the RP2040's internal pulldown so no external resistor is needed.

Firmware

Uses the Earle Philhower RP2040 core. Target board: Adafruit KB2040.

arduino-cli compile --fqbn rp2040:rp2040:adafruit_kb2040 controller/arduino-cli upload --fqbn rp2040:rp2040:adafruit_kb2040 controller/

Analog resolution: 12-bit (0–4095).

Serial protocol (115200 baud)

Send a single character, get CSV back:

CmdResponseExampleach1,ch2,ch3,ch42048,1023,3072,0bbutton (0/1)0ppress edges (0/1)1rrelease edges (0/1)0sbutton;ch1,ch2,ch3,ch40;2048,1023,3072,0

Display (optional)

Python tkinter GUI (display.py) shows live pot bars and button state. Requires pyserial.

pip install pyserialpython display.py

STLs

FileDescriptionCONTROLLER-BASE.stlEnclosure base — holds KB2040, pots, and buttonCONTROLLER-ARM1.stlPotentiometer knob — axis 1CONTROLLER-ARM2.stlPotentiometer knob — axis 2CONTROLLER-ARM3.stlPotentiometer knob — axis 3CONTROLLER-ARM4.stlPotentiometer knob — axis 4CONTROLLER-CLUTCH.stlClutch/gripper button cap

Designed in Blender — source file: CONTROLLER.blend

Notes

• Designed for the Earle Philhower RP2040 Arduino core
• Button uses INPUT_PULLDOWN — no external resistor required
• All four pots are read continuously; data is returned on request to avoid flooding the serial buffer