Servo Component

The servo component supports “RC” or “hobby” servo motors. These are small motors with built-in potentiometer position sensors, enabling you to control the angular position of the servo precisely.

As servos can use a lot of power, drawing voltage away from a board, you should power your servo with its own power supply in most cases. The following shows an example wiring diagram for a hobby servo wired to a pi board:

A diagram showing the signal wire of a servo connected to pin 16 on a Raspberry Pi. The servo’s power wires are connected to a 4.8V power supply.

The colors of the servo wires in this diagram may not match your servo. Refer to your servo’s data sheet for wiring specifications.

Most machines with a servo need at least the following hardware:

  • A board component that can run viam-server
  • A servo
  • A power supply for the board
  • A power supply for the servo

Supported models

To use your servo with Viam, check whether one of the following built-in models supports your servo.

Built-in models

For configuration information, click on the model name:

ModelDescription
fakeA model used for testing, with no physical hardware.
gpioA hobby servo wired to any model of board besides pi.
piA hobby servo wired to a Raspberry Pi board.

Control your servo with Viam’s client SDK libraries

To get started using Viam’s SDKs to connect to and control 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 generated.

When executed, this sample code will create a connection to your machine as a client. Then control your machine programmatically by adding API method calls as shown in the following examples.

These examples assume you have a servo called "my_servo" configured as a component of your machine. If your servo has a different name, change the name in the code.

Be sure to import the servo package for the SDK you are using:

from viam.components.servo import Servo
import (
  "go.viam.com/rdk/components/servo"
)

API

The servo component supports the following methods:

Method NameDescription
MoveMove the servo to the desired angle.
GetPositionGet the current angle of the servo.
StopStop the servo.
GetGeometriesGet all the geometries associated with the servo in its current configuration, in the frame of the servo.
DoCommandSend or receive model-specific commands.
CloseSafely shut down the resource and prevent further use.

Move

Move the servo to the desired angle in degrees.

Parameters:

  • angle (int): The desired angle of the servo in degrees.
  • extra (Optional[Mapping[str, Any]]): Extra options to pass to the underlying RPC call.
  • timeout (Optional[float]): An option to set how long to wait (in seconds) before calling a time-out and closing the underlying RPC call.

Returns:

  • None

For more information, see the Python SDK Docs.

my_servo = Servo.from_robot(robot=robot, name="my_servo")

# Move the servo from its origin to the desired angle of 30 degrees.
await my_servo.move(30)

Parameters:

  • ctx (Context): A Context carries a deadline, a cancellation signal, and other values across API boundaries.
  • angleDeg (uint32): The desired angle of the servo in degrees.
  • extra (map[string]interface{}): Extra options to pass to the underlying RPC call.

Returns:

  • (error): An error, if one occurred.

For more information, see the Go SDK Docs.

// Move the servo from its origin to the desired angle of 30 degrees.
myServoComponent.Move(context.Background(), 30, nil)

GetPosition

Get the current set angle of the servo in degrees.

Parameters:

Returns:

  • (int): The current set angle of the servo in degrees.

For more information, see the Python SDK Docs.

my_servo = Servo.from_robot(robot=robot, name="my_servo")

# Get the current set angle of the servo.
pos1 = await my_servo.get_position()

# Move the servo from its origin to the desired angle of 20 degrees.
await my_servo.move(20)

# Get the current set angle of the servo.
pos2 = await my_servo.get_position()

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:

  • (uint32): The current set angle of the servo in degrees.
  • (error): An error, if one occurred.

For more information, see the Go SDK Docs.

// Get the current set angle of the servo.
pos1, err := myServoComponent.Position(context.Background(), nil)

// Move the servo from its origin to the desired angle of 20 degrees.
myServoComponent.Move(context.Background(), 20, nil)

// Get the current set angle of the servo.
pos2, err := myServoComponent.Position(context.Background(), nil)

logger.Info("Position 1: ", pos1)
logger.Info("Position 2: ", pos2)

Stop

Stop the servo from moving.

Parameters:

Returns:

  • None.

For more information, see the Python SDK Docs.

my_servo = Servo.from_robot(robot=robot, name="my_servo")

# Move the servo from its origin to the desired angle of 10 degrees.
await my_servo.move(10)

# Stop the servo. It is assumed that the servo stops moving immediately.
await my_servo.stop()

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.

For more information, see the Go SDK Docs.

// Move the servo from its origin to the desired angle of 10 degrees.
myServoComponent.Move(context.Background(), 10, nil)

// Stop the servo. It is assumed that the servo stops moving immediately.
myServoComponent.Stop(context.Background(), nil)

GetGeometries

Get all the geometries associated with the servo in its current configuration, in the frame of the servo. 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.

Parameters:

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

Returns:

For more information, see the Python SDK Docs.

my_servo = Servo.from_robot(robot=robot, name="my_servo")

geometries = await my_servo.get_geometries()

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

DoCommand

Execute model-specific commands that are not otherwise defined by the component API. For built-in models, model-specific commands are covered with each model’s documentation. If you are implementing your own servo and add features that have no built-in API method, you can access them with DoCommand.

Parameters:

Returns:

my_servo = Servo.from_robot(robot, "my_servo")

command = {"cmd": "test", "data1": 500}
result = my_servo.do(command)

For more information, see the Python SDK Docs.

Parameters:

Returns:

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

For more information, see the Go SDK Code.

Close

Safely shut down the resource and prevent further use.

Parameters:

  • None

Returns:

  • None
my_servo = Servo.from_robot(robot, "my_servo")

await my_servo.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.
err := myServoComponent.Close(ctx)

For more information, see the Go SDK Docs.

Troubleshooting

You can find additional assistance in the Troubleshooting section.

You can also ask questions in the Community Discord and we will be happy to help.

Next steps