Real-Time Data Exchange (RTDE) Guide

Introduction

The Real-Time Data Exchange (RTDE) interface provides a way to synchronize external applications with the UR controller over a standard TCP/IP connection, without breaking any real-time properties of the UR controller. This functionality is useful for interacting with fieldbus drivers (e.g., Ethernet/IP), manipulating robot I/O, and plotting robot status (e.g., robot trajectories). The RTDE interface is by default available when the UR controller is running.

The synchronization is configurable and can involve the following data:

  • Output: robot-, joint-, tool- and safety status, analog and digital I/O’s, and general-purpose output registers.

  • Input: digital and analog outputs and general-purpose input registers.

The RTDE functionality is split into two stages: a setup procedure and a synchronization loop. On connection to the RTDE interface, the client sets up the variables to be synchronized. The client sends a setup list of named input and output fields to be included in the data synchronization packages. This list is known as a recipe. Each successfully configured input recipe receives a unique recipe ID. Supported field names and their associated data types are listed below.

When the synchronization loop starts, the RTDE interface sends the requested data to the client in the specified order. The client sends updated inputs to the RTDE interface when values change. Data synchronization uses serialized binary data. Packages share a general structure with a header and a payload, if applicable.

Key Features

  • Real-time synchronization: The RTDE typically generates output messages at 125 Hz. However, if the controller lacks computational resources, it will skip some output packages and only send the most recent data.

  • Input messages: Variables in the controller can be updated via multiple messages. Inputs retain their last received value, and only one RTDE client can control a specific variable at any time.

  • Runtime environment: An RTDE client can run on the UR Control Box PC or any external PC. Running the RTDE client on the Control Box avoids network latency but may compete with the UR controller for resources.

  • Protocol changes: The RTDE protocol may be updated by UR. RTDE clients can request specific protocol versions to ensure compatibility.

Additional Resources

Reference implementation for RTDE protocol is available in GitHub repository. API documentation of the Python library is available on RTDE Client Python Module page

Field Names and Associated Types

Robot Controller Inputs

Name

Type

Comment

Introduced in Version

speed_slider_mask

UINT32

0 = don’t change speed slider, 1 = use speed_slider_fraction to set speed slider value

speed_slider_fraction

DOUBLE

New speed slider value

standard_digital_output_mask

UINT8

Standard digital output bit mask

configurable_digital_output_mask

UINT8

Configurable digital output bit mask

standard_digital_output

UINT8

Standard digital outputs

configurable_digital_output

UINT8

Configurable digital outputs

standard_analog_output_mask

UINT8

Standard analog output mask (Bits 0-1: standard_analog_output_0 | standard_analog_output_1)

standard_analog_output_type

UINT8

Output domain {0=current[mA], 1=voltage[V]} (Bits 0-1: standard_analog_output_0 | standard_analog_output_1)

standard_analog_output_0

DOUBLE

Standard analog output 0 (ratio) [0..1]

standard_analog_output_1

DOUBLE

Standard analog output 1 (ratio) [0..1]

input_bit_registers0_to_31

UINT32

General purpose bits reserved for FieldBus/PLC interface usage

input_bit_registers32_to_63

UINT32

General purpose bits reserved for FieldBus/PLC interface usage

input_bit_register_X

BOOL

64 general purpose bits (X: [64..127]) reserved for external RTDE clients

5.3.0

input_int_register_X

INT32

48 general purpose integer registers (X: [0..23] reserved for FieldBus/PLC, [24..47] for external RTDE clients)

[24..47] 5.3.0

input_double_register_X

DOUBLE

48 general purpose double registers (X: [0..23] reserved for FieldBus/PLC, [24..47] for external RTDE clients)

[24..47] 5.3.0

external_force_torque

VECTOR6D

Input external wrench when using ft_rtde_input_enable builtin

Robot Controller Outputs

NOTE: Robot controller requires that client subscribes to at least one output. Client should read data periodically from the socket. Connection is closed by robot controller when receive buffer overflows.

Name

Type

Comment

Introduced in Version

timestamp

DOUBLE

Time elapsed since the controller was started [s]

target_q

VECTOR6D

Target joint positions

target_qd

VECTOR6D

Target joint velocities

target_qdd

VECTOR6D

Target joint accelerations

target_current

VECTOR6D

Target joint currents

target_moment

VECTOR6D

Target joint moments (torques)

actual_q

VECTOR6D

Actual joint positions

actual_qd

VECTOR6D

Actual joint velocities

actual_current

VECTOR6D

Actual joint currents

actual_current_window

VECTOR6D

Allowed deviations from target currents

actual_current_as_torque

VECTOR6D

Actual joint currents converted to torques

5.23.0 / 10.11.0

joint_control_output

VECTOR6D

Joint control currents

actual_TCP_pose

VECTOR6D

Actual Cartesian coordinates of the tool: (x,y,z,rx,ry,rz) where rx, ry and rz is a rotation vector representation of the tool orientation

actual_TCP_speed

VECTOR6D

Actual speed of the tool in Cartesian coordinates. The speed is given in [m/s] and the rotational part of the TCP speed (rx, ry, rz) is the angular velocity given in [rad/s]

actual_TCP_force

VECTOR6D

Generalized forces in the. It compensates the measurement for forces and torques generated by the payload

target_TCP_pose

VECTOR6D

Target Cartesian coordinates of the tool: (x,y,z,rx,ry,rz), where rx, ry and rz is a rotation vector representation of the tool orientation

target_TCP_speed

VECTOR6D

Target speed of the tool in Cartesian coordinates. The speed is given in [m/s] and the rotational part of the TCP speed (rx, ry, rz) is the angular velocity given in [rad/s]

actual_digital_input_bits

UINT64

Current state of the digital inputs (0-7: Standard, 8-15: Configurable, 16-17: Tool)

joint_temperatures

VECTOR6D

Temperature of each joint in degrees Celsius

actual_execution_time

DOUBLE

Controller real-time thread execution time [ms]

robot_mode

INT32

Robot mode

joint_mode

VECTOR6INT32

Joints control mode

safety_mode

INT32

Safety mode

safety_status

INT32

Safety status

5.4.0

actual_tool_accelerometer

VECTOR3D

Tool x, y, and z accelerometer values

speed_scaling

DOUBLE

Speed scaling of the trajectory limiter

target_speed_fraction

DOUBLE

Target speed fraction

actual_momentum

DOUBLE

Norm of cartesian linear momentum

actual_main_voltage

DOUBLE

Safety Control Board: Main voltage

actual_robot_voltage

DOUBLE

Safety Control Board: Robot voltage (48V)

actual_robot_current

DOUBLE

Safety Control Board: Robot current

actual_joint_voltage

VECTOR6D

Actual joint voltages [V]

actual_digital_output_bits

UINT64

Current state of the digital outputs (0-7: Standard, 8-15: Configurable, 16-17: Tool)

runtime_state

UINT32

Program state

elbow_position

VECTOR3D

Position of robot elbow in Cartesian Base Coordinates

elbow_velocity

VECTOR3D

Velocity of robot elbow in Cartesian Base Coordinates

robot_status_bits

UINT32

Bits 0-3: Is power on, Is program running, Is teach button pressed, Is power button

safety_status_bits

UINT32

Bits 0-10: Is normal mode, Is reduced mode, Is protective stopped, Is recovery mode,
Is safeguard stopped, Is system emergency stopped, Is robot emergency stopped, Is emergency stopped,
Is violation, Is fault, Is stopped due to safety

analog_io_types

UINT32

Bits 0-3: analog input 0, analog input 1, analog output 0, analog output 1 (0=current[mA], 1=volt[V])

standard_analog_input_0

DOUBLE

Standard analog input 0 [mA or V]

standard_analog_input_1

DOUBLE

Standard analog input 1 [mA or V]

standard_analog_output_0

DOUBLE

Standard analog output 0 [mA or V]

standard_analog_output_1

DOUBLE

Standard analog output 1 [mA or V]

io_current

DOUBLE

I/O current [mA]

input_bit_registers0_to_31

UINT32

General purpose bits reserved for FieldBus/PLC interface

input_bit_registers32_to_63

UINT32

General purpose bits reserved for FieldBus/PLC interface

input_bit_register_X

BOOL

64 general purpose bits (X: [64..127]) reserved for external RTDE clients

5.3.0

input_int_register_X

INT32

48 general purpose integer registers (X: [0..23] reserved for FieldBus/PLC, [24..47] for external RTDE clients)

[24..47] 5.3.0

input_double_register_X

DOUBLE

48 general purpose double registers (X: [0..23] reserved for FieldBus/PLC, [24..47] for external RTDE clients)

[24..47] 5.3.0

output_bit_registers0_to_31

UINT32

General purpose bits reserved for FieldBus/PLC interface

output_bit_registers32_to_63

UINT32

General purpose bits reserved for FieldBus/PLC interface

output_bit_register_X

BOOL

64 general purpose bits (X: [64..127]) reserved for external RTDE clients

5.3.0

output_int_register_X

INT32

48 general purpose integer registers (X: [0..23] reserved for FieldBus/PLC, [24..47] for external RTDE clients)

[24..47] 5.3.0

output_double_register_X

DOUBLE

48 general purpose double registers (X: [0..23] reserved for FieldBus/PLC, [24..47] for external RTDE clients)

[24..47] 5.3.0

output_bit_registers

UINT32

32 general purpose bits (0-31) reserved for FieldBus/PLC interface usage

output_int_register_X

INT32

48 general purpose integer registers (X: [0..23] reserved for FieldBus/PLC, [24..47] for external RTDE clients)

[24..47] 5.3.0

output_double_register_X

DOUBLE

48 general purpose double registers (X: [0..23] reserved for FieldBus/PLC, [24..47] for external RTDE clients)

[24..47] 5.3.0

actual_robot_energy_consumed

DOUBLE

Robot Arm energy consumption since controller startup [Wh].

5.23.0 / 10.11.0

actual_robot_braking_energy_dissipated

DOUBLE

Robot Arm braking energy dissipated since controller startup [Wh]. This energy is flowing back into the Control Box and gets dissipated as heat.

5.23.0 / 10.11.0

encoder0_raw

INT32

Raw encoder0 counter with range of [-2³¹, 2³¹]

encoder1_raw

INT32

Raw encoder1 counter with range of [-2³¹, 2³¹]

euromap67_input_bits

UINT32

Euromap67 input bits

euromap67_output_bits

UINT32

Euromap67 output bits

euromap67_24V_voltage

DOUBLE

Euromap 24V voltage [V]

euromap67_24V_current

DOUBLE

Euromap 24V current [mA]

tool_mode

UINT32

One of tool mode constants

tool_analog_input_types

UINT32

Output domain (0=current[mA], 1=voltage[V]) Bits 0-1: Analog inputs

tool_analog_input0

DOUBLE

Tool analog input 0 [mA or V]

tool_analog_input1

DOUBLE

Tool analog input 1 [mA or V]

tool_output_voltage

INT32

Tool output voltage [V]

tool_output_current

DOUBLE

Tool current [mA]

tool_temperature

DOUBLE

Tool temperature in degrees Celsius

tool_output_mode

UINT8

The current output mode for tool digital outputs (0=Output, 1=Power)

tool_digital_output0_mode

UINT8

The current mode of digital output 0 (0=Disabled, 1=Sinking current, 2=Sourcing current, 3=Push/Pull)

tool_digital_output1_mode

UINT8

The current mode of digital output 1 (0=Disabled, 1=Sinking current, 2=Sourcing current, 3=Push/Pull)

tcp_force_scalar

DOUBLE

TCP force scalar [N]

joint_position_deviation_ratio

DOUBLE

A C153 or C159 protective stop is triggered if the value is ever equal to or exceeds 1.0

collision_detection_ratio

DOUBLE

A C157 or C158 protective stop is triggered if the value is ever equal to or exceeds 1.0

5.15.0

ft_raw_wrench

VECTOR6D

Raw force and torque measurement given in the Tool Flange frame.
Not compensated for forces and torques caused by the payload. Not zeroed by zero_ftsensor().

5.9.0

wrench_calc_from_currents

VECTOR6D

The forces and torques derived from the joint currents

payload

DOUBLE

Payload mass [Kg]

payload_cog

VECTOR3D

Payload Center of Gravity (CoGx, CoGy, CoGz) [m]

5.5.0

payload_inertia

VECTOR6D

Payload inertia matrix elements (Ixx,Iyy,Izz,Ixy,Ixz,Iyz) [kg*m²]

5.11.0

script_control_line

UINT32

Script line number that is actually in control of the robot given the robot is locked by one of the threads in the script.
If no thread is locking the robot this field is set to ‘0’. Script line number should not be confused with program tree line number displayed on polyscope.

5.9.0

time_scale_source

INT32

One of the constants from Time Scale Source

5.17.0

Time Scale Source

List of possible causes for time scaling.

Value

Description

-1

Other

0

Program is not running

1

Speed is not scaled

2

Joint torque limit reached

3

Joint acceleration limit reached

4

Power supply limit reached

5

Momentum safety limit reached

6

Stopping time safety limit reached

7

Stopping distance safety limit reached

8

Tool speed safety limit reached

9

Elbow speed safety limit reached

10

Joint speed safety limit reached

11

Smooth transition after safety state change

12

Stopping distance defined through safety API reached

13

User defined tool wrench limit reached

14

Scaling due to external axis speed limit

15

Saling due to external axis stopping

Data types

Name

Type

Size in bits

BOOL

0 = False, everything else = True

8

UINT8

unsigned integer

8

UINT32

unsigned integer

32

UINT64

unsigned integer

64

INT32

signed integer, two’s complement

32

DOUBLE

IEEE 754 floating point

64

VECTOR3D

3xDOUBLE

3x64

VECTOR6D

6xDOUBLE

6x64

VECTOR6INT32

6xINT32

6x32

VECTOR6UINT32

6xUINT32

6x32

STRING

ASCII char array

lengthx8

Network byte order

Protocol

EE = External Executable

CON = Robot Controller

Output: CON -> EE

Input: CON <- EE

RTDE_REQUEST_PROTOCOL_VERSION

Field name

Data Type

package size

uint16_t

package type

uint8_t

protocol version

uint16_t

Request the controller to work with “protocol version”

Direction: EE -> CON

Return

Field name

Data Type

package size

uint16_t

package type

uint8_t

accepted

uint8_t

The controller accepts or not, i.e. either 1 (success) or 0 (failed). On success, the EE should speak the specified protocol version and the CON will answer in that version.

RTDE_GET_URCONTROL_VERSION

Field name

Data Type

package size

uint16_t

package type

uint8_t

Retrieves the CON major, minor, bugfix and build number.

Direction: EE -> CON

Return

Field name

Data Type

package size

uint16_t

package type

uint8_t

major

uint32_t

minor

uint32_t

bugfix

uint32_t

build

uint32_t

The major, minor, bugfix and build number.

RTDE_TEXT_MESSAGE (protocol v. 1)

Direction: CON -> EE

Field name

Data Type

package size

uint16_t

package type

uint8_t

message type

uint8_t

message

string

Direction: EE -> CON

Field name

Data Type

package size

uint16_t

package type

uint8_t

message length

uint8_t

message

string

source length

uint8_t

source

string

warning level

uint8_t

Send an exception, error, warning or info message.

Warning level: EXCEPTION_MESSAGE, ERROR_MESSAGE, WARNING_MESSAGE, INFO_MESSAGE

EE->CON: Exceptions indicate EE program failure without recovery possibilities. Error, warning and info will end up in the PolyScope log.

CON -> EE: Indicates mainly different kinds of protocol failures.

Direction: See above

Return: Not available.

RTDE_TEXT_MESSAGE (protocol v. 2)

Field name

Data Type

package size

uint16_t

package type

uint8_t

message length

uint8_t

message

string

source length

uint8_t

source

string

warning level

uint8_t

Send an exception, error, warning or info message.

Warning level: EXCEPTION_MESSAGE, ERROR_MESSAGE, WARNING_MESSAGE, INFO_MESSAGE

EE->CON: Exceptions indicate EE program failure without recovery possibilities. Error, warning and info will end up in the PolyScope log.

CON -> EE: Indicates mainly different kinds of protocol failures.

Direction: Bilateral

Return: Not available.

RTDE_DATA_PACKAGE

Field name

Data Type

package size

uint16_t

package type

uint8_t

recipe id

uint8_t

<variable>

<data type>

An update to the CON/EE inputs respectively.

The <variable>s are packaged/serialized binary and match the type specified by the SETUP_OUTPUTS or SETUP_INPUTS requests return.

Direction: Bilateral

Return: Not available

RTDE_CONTROL_PACKAGE_SETUP_OUTPUTS (protocol v. 1)

Field name

Data Type

package size

uint16_t

package type

uint8_t

variable names

string

Setup the outputs recipe. At the moment the CON only supports one output recipe. The package should contain all desired output variables. The variables names is a list of comma separated variable name strings.

Direction: EE -> CON

Return

Field name

Data Type

package size

uint16_t

package type

uint8_t

variable types

string

Returns the variable types in the same order as they were supplied in the request.

Variable types: VECTOR6D, VECTOR3D, VECTOR6INT32, VECTOR6UINT32, DOUBLE, UINT64, UINT32, INT32, BOOL, UINT8

If a variable is not available, then the variable type will be “NOT_FOUND”.

In case of one or more “NOT_FOUND” return values, the recipe is considered invalid and the RTDE will not output this data.

RTDE_CONTROL_PACKAGE_SETUP_OUTPUTS (protocol v. 2)

Field name

Data Type

package size

uint16_t

package type

uint8_t

output frequency

double

variable names

string

Setup the outputs recipe. At the moment the CON only supports one output recipe and the output frequency is configurable. The frequency must be between 1 and 500 Hz and the output rate will be according to floor(500 / frequency).

The package should contain all desired output variables.

The variable names is a list of comma separated variable name strings.

Direction: EE -> CON

Return

Field name

Data Type

package size

uint16_t

package type

uint8_t

output recipe id

uint8_t

variable types

string

Returns the variable types in the same order as they were supplied in the request.

Variable types: VECTOR6D, VECTOR3D, VECTOR6INT32, VECTOR6UINT32, DOUBLE, UINT64, UINT32, INT32, BOOL, UINT8

If a variable is not available, then the variable type will be “NOT_FOUND”.

In case of one or more “NOT_FOUND” return values, the recipe is considered invalid and the RTDE will not output this data (output recipe id = 0).

RTDE_CONTROL_PACKAGE_SETUP_INPUTS

Field name

Data Type

package size

uint16_t

package type

uint8_t

variable names

string

Setup a CON input recipe.The CON supports 255 different input recipes (0 is reserved). The variables names is a list of comma separated variable name strings.

Direction: EE -> CON

Return

Field name

Data Type

package size

uint16_t

package type

uint8_t

input recipe id

uint8_t

variable types

string

Returns the variable types in the same order as they were supplied in the request.

Variable types: VECTOR6D, VECTOR3D, VECTOR6INT32, VECTOR6UINT32, DOUBLE, UINT64, UINT32, INT32, BOOL, UINT8

If a variable has been claimed by another EE, then the variable type will be “IN_USE”.

If a variable is not available, then the variable type will be “NOT_FOUND”.

In case of one or more “IN_USE” or “NOT_FOUND” return values, the recipe is considered invalid (input recipe id = 0).

RTDE_CONTROL_PACKAGE_START

Field name

Data Type

package size

uint16_t

package type

uint8_t

Request the controller to start sending output updates. This will fail if e.g. an output package has not been configured yet.

Direction: EE -> CON

Return

Field name

Data Type

package size

uint16_t

package type

uint8_t

accepted

uint8_t

The CON accepts or not. Either 1 (success) or 0 (failed).

RTDE_CONTROL_PACKAGE_PAUSE

Field name

Data Type

package size

uint16_t

package type

uint8_t

Request the CON to pause sending output updates.

Direction: EE -> CON

Return

Field name

Data Type

package size

uint16_t

package type

uint8_t

accepted

uint8_t

The CON will always accept a pause command and return a 1 (success).