dora-teleop

A dora-rs node that hands a robot arm to a human. Pick up a gamepad and move the arm, or open a browser and move it from there — one of the two at a time, decided here.

It drives dora-ulite6 through that node's ordinary jog and request ports, and talks to the browser through dora-websocket-transceiver. It contains no web server and no robot driver: it is the piece in the middle that decides what the arm should be doing, and that decision is the only thing it owns.

The gamepad

Analog and blended — several axes at once, and how fast depends on how far you push. That is the whole reason a pad beats the web console's four-sector dial pad, which can only ask for one axis at a time at one fixed speed.

Control	Does	Units
Left stick	Move along X (up/down) and Y (left/right)	mm/s
Triggers	Lift on the right, lower on the left	mm/s
Right stick	Roll (left/right) and pitch (up/down)	deg/s
Bumpers	Yaw, left and right	deg/s
A	Close the tool	—
B	Open the tool	—
X	Clear a controller error	—
Y	Toggle freedrive	—
Back	E-STOP	—

Up on the stick sends the arm away from you, along +X in the robot's base frame — the same convention the web console's dial uses, so the two agree.

Indices are SDL's, which is what most Xbox- and PlayStation-style pads report. A pad that disagrees is a change to Layout in dora_teleop/mapping.py rather than a new environment variable: an index nobody can verify from outside is worse than a line of code somebody can read.

home is deliberately not on the pad. It is a large unattended motion and belongs behind a deliberate click, not a thumb resting on a face button.

The lease

Two sources, one arm. Whoever holds the lease drives; the other is ignored.

• The gamepad takes it implicitly, the first time a stick moves, if nobody holds it. Nobody should have to reach for a browser to use the thing in their hands.
• It gives it back after GAMEPAD_IDLE_RELEASE_S untouched, so a pad left on the bench does not lock the browser out forever.
• The browser takes it explicitly, with the console's TAKE CONTROL button, and gives it back with RELEASE. It can preempt a held arm, because an operator who can see the arm is better placed than this code to decide they should have it.
• E-STOP is never gated. From either source, held lease or not. Somebody reaching for the stop is the one moment when asking who owns the arm is the wrong question.

The lease binds only what goes through this node. dora-ulite6 has no idea it exists. Another node publishing request will preempt an operator mid-motion and nothing here can stop it — if that matters for your dataflow, do not wire one.

The deadman

An arm under a velocity command keeps moving until told otherwise, so the question is never whether to start but whether anything has happened that means it must stop. Three layers, outermost last:

1. Re-send every tick (50 ms) while a source is driving.
2. This node's watchdog (JOG_TTL_S, 0.4 s) stops the arm when the owner goes quiet — and stops it immediately, without waiting out the timer, when the gamepad is unplugged or the last browser disconnects. An unplugged pad is not a centred pad.
3. The arm's own expiry (VELOCITY_COMMAND_TTL_S in dora-ulite6, 0.5 s), enforced by the controller whether or not this process is alive.

Keep them in that order. If this node's timer is longer than the controller's, the backstop fires before the thing it is backing up.

On shutdown the node sends one all-zero velocity before exiting. A motion lives in the controller, not in this process.

The stop is sent once, not every tick. A stream of zeroes would keep dora-ulite6 believing a jog is live and hold robot_state at moving forever.

Ports

Direction	Name	Description
in	tick	50 ms — re-send, deadman, telemetry
in	ui_command	One console message, from the bridge's data_out
in	clients	Connect/disconnect from the bridge — the web deadman
in	response	An answer from the arm
in	motion_state	How a motion ended
in	robot_state	The arm's own state
in	tcp_pose	Tool-tip pose, six float32, mm and degrees
in	joint_pose	Joint angles, six float32, degrees
out	jog	{velocity: [vx, vy, vz, wx, wy, wz]}, mm/s + deg/s
out	request	A service call, request_id in the metadata
out	ui_state	The console's telemetry snapshot, as JSON

Environment Variables

Variable	Default	Description
SPEED_MM_S	60.0	Translation speed at full deflection
SPEED_DEG_S	30.0	Rotation speed at full deflection
DEADZONE	0.12	Stick travel near centre to ignore
EXPO	0.4	How much of the curve is cubic; 0 is linear
JOYSTICK_INDEX	0	Which pad to open
JOG_TTL_S	0.4	Owner silence before the arm is stopped
GAMEPAD_IDLE_RELEASE_S	2.0	Untouched pad before it hands the arm back
STATE_POLL_S	0.5	How often to ask the arm what telemetry does not carry

A value that cannot be read, a DEADZONE outside the stick or an EXPO off the curve stops the node at startup rather than the first time somebody picks up the pad.

Usage

See dataflow.yml for the whole stack wired together. The short version:

  - id: teleop
    git: ssh://git@gitea.liria.cl:5001/liria/dora-teleop.git
    tag: v0.1.0
    build: pip install .
    path: dora-teleop
    inputs:
      tick: dora/timer/millis/50
      ui_command: ws-transceiver/data_out
      clients: ws-transceiver/clients
      response: ulite6/response
      motion_state: ulite6/motion_state
      robot_state: ulite6/robot_state
      tcp_pose: ulite6/tcp_pose
      joint_pose: ulite6/joint_pose
    outputs: [jog, request, ui_state]

dora run dataflow.yml --uv

Requirements: dora 1.0+ (verified with dora-cli 1.0.1), Python 3.11+, uv, and a gamepad if you want one — the node starts without and says so.

Development

uv sync --group dev
uv run pytest      # 66 tests, no gamepad, arm, browser or daemon needed
uv run ruff check .
uv run ruff format --check .

dora_teleop/gamepad.py is the only file that touches pygame, and the only one that cannot be tested without hardware. Everything else sees a plain Sample.