Introduction

The Waveshare RoArm family consists of two product lines — the M2 (4-DOF) and the M3 (5+1-DOF) — designed for flexible mounting on mobile platforms. Both combine lightweight carbon-fiber construction with enough torque for real workloads, and share the same ESP32 control board, JSON command protocol, and WiFi/serial/ESP-NOW interfaces.

RoArm-M2-S — Image: Waveshare

RoArm-M3 — Image: Waveshare

Model Comparison

M2 vs M3

The M2 is a 4-DOF arm with a single-axis end-effector. The M3 extends this with a 2-DOF articulated wrist (pitch + rotation), bringing the total to 5+1 DOF and 7 servos. The extra wrist dexterity comes at the cost of payload — 0.2 kg vs 0.5 kg at 0.5m reach — because the additional servos add mass to the end of the kinematic chain. The M3 also adds LeRobot support for ML-based teleoperation and an upgraded sensor suite (INA219 voltage monitor, AK09918C compass, QMI8658 6-axis IMU, TF card slot).

	M2-S	M2-Pro	M3-S	M3-Pro
DOF	4	4	5+1	5+1
Servos	5× ST3215 (plastic)	5× ST3235 (all-metal)	7× ST3215/HS (plastic)	7× ST3235 (all-metal)
Wrist	Single axis	Single axis	2-DOF (pitch + rotation)	2-DOF (pitch + rotation)
Torque	30 kg.cm @ 12V	30 kg.cm @ 12V	30 kg.cm @ 12V	30 kg.cm @ 12V
Weight	826g ± 15g	873g ± 15g	973.5g ± 15g	1020.8g ± 15g
Payload	0.5kg @ 0.5m	0.5kg @ 0.5m	0.2kg @ 0.5m	0.2kg @ 0.5m
Workspace	1090mm × 798mm	1090mm × 798mm	1120mm × 798mm	1120mm × 798mm
Precision	≈ ±4mm	≈ ±4mm	≈ ±5mm	≈ ±5mm
LeRobot	—	—	Yes	Yes
Backlash	May increase with wear	Stable over time	May increase with wear	Stable over time
Firmware	Identical	Identical	Identical	Identical
Price	~$224	~$332	~$190–331	~$300–456

Standard vs Pro

Within each product line, the difference between “-S” and “-Pro” is purely mechanical — the Pro models use all-metal ST3235 servo housings for greater durability and tighter long-term backlash. The control board, firmware, and JSON command set are identical.

Tip

Choosing a model: The M2-S is the best starting point for prototyping, education, and light-duty tasks. Choose the M2-Pro for heavy continuous use where long-term positional consistency matters. Step up to the M3 when you need wrist dexterity — orientation control, tool rotation, or ML-based manipulation via LeRobot. The M3-Pro adds all-metal durability to the M3’s expanded kinematic chain.

Everything in this documentation applies to all models unless noted otherwise. M3-specific features (wrist joints, LeRobot, additional sensors) are called out where relevant.

Joint Architecture

M2 (4-DOF)

The M2 has four actuated joints, each driven by serial bus servos with 12-bit magnetic encoders:

Joint	Range	Direction Convention	Notes
Base	360° continuous	+ = left	Omnidirectional rotation
Shoulder	~180°	+ = down	Dual-drive (two servos) for double torque
Elbow	~180°	+ = down	Single servo
End-Effector	~180°	+ = grab/down	Configurable as gripper or wrist

M3 (5+1-DOF)

The M3 extends the M2 kinematic chain with a 2-DOF articulated wrist, adding pitch and rotation control before the gripper:

Joint	Range	Direction Convention	Notes
Base	360° continuous	+ = left	Omnidirectional rotation
Shoulder	~180°	+ = down	Dual-drive (two servos) for double torque
Elbow	~225°	+ = down	Extended range vs M2
Wrist Pitch	~180°	+ = down	M3 only — vertical wrist articulation
Wrist Rotation	~360°	+ = CW	M3 only — axial tool rotation
Gripper	~180°	+ = grab	End-effector

The dual-drive shoulder design is shared across both lines — two servos mechanically coupled to the same joint output shaft, effectively doubling the available torque without adding a gearbox.

RoArm-M2 joints — Image: Waveshare

RoArm-M3 joints — the 2-DOF wrist adds pitch (servo 15) and rotation (servo 16) between the elbow and gripper. Image: Waveshare

Workspace

The 360° base rotation combined with the shoulder and elbow joints creates a roughly spherical workspace with a diameter of about 1 meter. The exact reachable envelope depends on the EoAT (End of Arm Tooling) configuration.

RoArm-M2 workspace — Image: Waveshare

RoArm-M3 workspace — the additional wrist link extends the reach envelope slightly. Image: Waveshare

Materials and Construction

• Arm links: Carbon fiber tubes with 5052 aluminum alloy brackets
• Base plate: Machined aluminum with mounting holes
• Servo housings: Aluminum heat-sink brackets (“-S” models: plastic shell; “-Pro” models: all-metal)
• Total weight: 826g (M2-S) / 873g (M2-Pro) / 973.5g (M3-S) / 1020.8g (M3-Pro), arm body only

Safety

Moving Parts Hazard

The arm can move unexpectedly if it receives commands while powered. Always ensure the workspace is clear before sending motion commands.

1. Emergency stop: Send {"T":0} to immediately halt all motion
2. Reset: Send {"T":999} to clear the emergency flag after resolving the issue
3. Torque lock: Use {"T":210,"cmd":0} to release all servo torque (arm will go limp)

Caution

The servos draw significant current during fast movements. Use a 12V / 5A power supply. 3S lithium batteries (11.1V nominal) also work. USB power alone cannot drive the motors.

What’s in the Box

Both models include:

• RoArm-M2 arm assembly (pre-built)
• General Driver for Robots board (ESP32-based, with 9-DOF IMU and 0.91” OLED)
• 12V / 5A power adapter
• USB-C cable (for programming/serial)
• Table-edge fixing clamp (supports edges up to 72mm)
• Camera mount
• Expansion plate and mounting hardware
• Gripper end-effector (pre-installed)

Servo IDs

M2 (5 servos)

Servo ID	Joint
11	Base
12	Shoulder (driving)
13	Shoulder (driven)
14	Elbow
15	Gripper / End-effector

M3 (7 servos)

Servo ID	Joint
11	Base
12	Shoulder (driving)
13	Shoulder (driven)
14	Elbow
15	Wrist pitch
16	Wrist rotation
17	Gripper

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Hardware details from the Waveshare Wiki and RoArm-M3 Wiki. Images: Waveshare.