Edit

Encoder API

The encoder API allows you to give commands to your encoder components for getting the position of a motor or a joint in ticks or degrees.

The encoder component supports the following methods:

Method Name	Description	`viam-micro-server` Support
`GetPosition`	Get the current position of the encoder in ticks or degrees.
`ResetPosition`	Set the current position of the encoder to be the new zero position.
`GetProperties`	Get a list of all the position types that are supported by a given encoder.
`GetGeometries`	Get all the geometries associated with the encoder in its current configuration, in the frame of the encoder.
`Reconfigure`	Reconfigure this resource.
`DoCommand`	Execute model-specific commands that are not otherwise defined by the component API.
`GetResourceName`	Get the `ResourceName` for this encoder with the given name.
`Close`	Safely shut down the resource and prevent further use.

Establish a connection

To get started using Viam’s SDKs to connect to and control your encoder and the rest of your machine, go to your machine’s page on the Viam app, Navigate to the CONNECT tab’s Code sample page, select your preferred programming language, and copy the sample code.

To show your machine’s API key in the sample code, toggle Include API key.

Caution: Keep your API key and machine address safe

We strongly recommend that you add your API key and machine address as an environment variable. Anyone with these secrets can access your machine, and the computer running your machine.

When executed, this sample code creates a connection to your machine as a client.

The following examples assume you have an encoder called "my_encoder" configured as a component of your machine. If your encoder has a different name, change the name in the code.

Import the encoder package for the SDK you are using:

Python
Go

from viam.components.encoder import Encoder

import (
  "go.viam.com/rdk/components/encoder"
)

API

GetPosition

Get the current position of the encoder in ticks or degrees. Relative encoders return ticks since last zeroing. Absolute encoders return degrees. Supported by viam-micro-server.

Python
Go

Parameters:

position_type (viam.proto.component.encoder.PositionType.ValueType) (optional): The desired output type of the position.
extra (Mapping[str, Any]) (optional): Extra options to pass to the underlying RPC call.
timeout (float) (optional): An option to set how long to wait (in seconds) before calling a time-out and closing the underlying RPC call.

Returns:

(Tuple[float, PositionType.ValueType]): A tuple containing two values; the first [0] the position of the encoder which can either be ticks since last zeroing for a relative encoder or degrees for an absolute encoder, and the second [1] the type of position the encoder returns (ticks or degrees).

Example:

my_encoder = Encoder.from_robot(robot=machine, name='my_encoder')

# Get the position of the encoder in ticks
position = await my_encoder.get_position(PositionType.POSITION_TYPE_TICKS_COUNT)
print("The encoder position is currently ", position[0], position[1])

For more information, see the Python SDK Docs.

Parameters:

ctx (Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.
positionType (PositionType): Specify whether to get the current position in ticks (encoder.PositionTypeTicks) or in degrees (encoder.PositionTypeDegrees). If you are not sure which position type your encoder supports but it is a built-in Viam-supported model, you can leave this parameter unspecified (encoder.PositionTypeUnspecified) and it will default to the correct position type.
extra (map[string]interface{}): Extra options to pass to the underlying RPC call.

Returns:

(float64): The current position (measured in ticks or degrees).
(PositionType): The type of position the encoder returns (ticks or degrees).
(error): An error, if one occurred.

Example:

myEncoder, err := encoder.FromRobot(machine, "my_encoder")
if err != nil {
  logger.Fatalf("cannot get encoder: %v", err)
}

// Get the position of the encoder in ticks
position, posType, err := myEncoder.Position(context.Background(), encoder.PositionTypeTicks, nil)

For more information, see the Go SDK Docs.

ResetPosition

Set the current position of the encoder to be the new zero position. Supported by viam-micro-server.

Python
Go

Parameters:

extra (Mapping[str, Any]) (optional): Extra options to pass to the underlying RPC call.
timeout (float) (optional): An option to set how long to wait (in seconds) before calling a time-out and closing the underlying RPC call.

Returns:

None.

Example:

my_encoder = Encoder.from_robot(robot=machine, name='my_encoder')

# Reset the zero position of the encoder.
await my_encoder.reset_position()

For more information, see the Python SDK Docs.

Parameters:

ctx (Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.
extra (map[string]interface{}): Extra options to pass to the underlying RPC call.

Returns:

(error): An error, if one occurred.

Example:

myEncoder, err := encoder.FromRobot(machine, "my_encoder")
if err != nil {
  logger.Fatalf("cannot get encoder: %v", err)
}

err = myEncoder.ResetPosition(context.Background(), nil)

For more information, see the Go SDK Docs.

GetProperties

Get a list of all the position types that are supported by a given encoder. Supported by viam-micro-server.

Python
Go

Parameters:

extra (Mapping[str, Any]) (optional): Extra options to pass to the underlying RPC call.
timeout (float) (optional): An option to set how long to wait (in seconds) before calling a time-out and closing the underlying RPC call.

Returns:

(viam.components.encoder.encoder.Encoder.Properties): Map of position types to supported status.

Example:

my_encoder = Encoder.from_robot(robot=machine, name='my_encoder')

# Get whether the encoder returns position in ticks or degrees.
properties = await my_encoder.get_properties()

For more information, see the Python SDK Docs.

Parameters:

ctx (Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.
extra (map[string]interface{}): Extra options to pass to the underlying RPC call.

Returns:

(Properties): The position types supported by the encoder model.
(error): An error, if one occurred.

Example:

myEncoder, err := encoder.FromRobot(machine, "my_encoder")

// Get whether the encoder returns position in ticks or degrees.
properties, err := myEncoder.Properties(context.Background(), nil)

For more information, see the Go SDK Docs.

GetGeometries

Get all the geometries associated with the encoder in its current configuration, in the frame of the encoder. The motion and navigation services use the relative position of inherent geometries to configured geometries representing obstacles for collision detection and obstacle avoidance while motion planning.

Python

Parameters:

extra (Mapping[str, Any]) (optional): Extra options to pass to the underlying RPC call.
timeout (float) (optional): An option to set how long to wait (in seconds) before calling a time-out and closing the underlying RPC call.

Returns:

(List[viam.proto.common.Geometry]): The geometries associated with the Component.

Example:

my_encoder = Encoder.from_robot(robot=machine, name="my_encoder")
geometries = await my_encoder.get_geometries()

if geometries:
    # Get the center of the first geometry
    print(f"Pose of the first geometry's centerpoint: {geometries[0].center}")

For more information, see the Python SDK Docs.

Reconfigure

Reconfigure this resource. Reconfigure must reconfigure the resource atomically and in place.

Parameters:

ctx (Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.
deps (Dependencies): The resource dependencies.
conf (Config): The resource configuration.

Returns:

(error): An error, if one occurred.

For more information, see the Go SDK Docs.

DoCommand

Execute model-specific commands that are not otherwise defined by the component API. If you are implementing your own encoder as a modular resource and are adding features that have no built-in API method, you can access them with DoCommand. Supported by viam-micro-server.

Python
Go

Parameters:

command (Mapping[str, ValueTypes]) (required): The command to execute.
timeout (float) (optional): An option to set how long to wait (in seconds) before calling a time-out and closing the underlying RPC call.

Returns:

(Mapping[str, viam.utils.ValueTypes]): Result of the executed command.

Raises:

(NotImplementedError): Raised if the Resource does not support arbitrary commands.

Example:

my_encoder = Encoder.from_robot(robot=machine, name="my_encoder")
command = {"cmd": "test", "data1": 500}
result = await my_encoder.do_command(command)

For more information, see the Python SDK Docs.

Parameters:

ctx (Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.
cmd (map[string]interface{}): The command to execute.

Returns:

(map[string]interface{}): The command response.
(error): An error, if one occurred.

Example:

myEncoder, err := encoder.FromRobot(machine, "my_encoder")

command := map[string]interface{}{"cmd": "test", "data1": 500}
result, err := myEncoder.DoCommand(context.Background(), command)

For more information, see the Go SDK Docs.

GetResourceName

Get the ResourceName for this encoder with the given name.

Python

Parameters:

name (str) (required): The name of the Resource.

Returns:

(viam.proto.common.ResourceName): The ResourceName of this Resource.

Example:

my_encoder_name = Encoder.get_resource_name("my_encoder")

For more information, see the Python SDK Docs.

Close

Safely shut down the resource and prevent further use.

Python
Go

Parameters:

None.

Returns:

None.

Example:

my_encoder = Encoder.from_robot(robot=machine, name="my_encoder")
await my_encoder.close()

For more information, see the Python SDK Docs.

Parameters:

ctx (Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.

Returns:

(error): An error, if one occurred.

Example:

myEncoder, err := encoder.FromRobot(machine, "my_encoder")

err = myEncoder.Close(context.Background())

For more information, see the Go SDK Docs.

Was this page helpful?

Glad to hear it! If you have any other feedback please let us know:

We're sorry about that. To help us improve, please tell us what we can do better:

Thank you!