Control a motor in 2 minutes

package main

import (
  "context"
  "time"

  "go.viam.com/rdk/logging"
  "go.viam.com/utils/rpc"
  "go.viam.com/rdk/robot/client"
  "go.viam.com/rdk/components/motor")

func main() {
  logger := logging.NewDebugLogger("client")
  machine, err := client.New(
    context.Background(),
    // Replace "<YOUR MACHINE ADDRESS>" (including brackets) with your machine's address
    "<YOUR MACHINE ADDRESS>",
    logger,
    client.WithDialOptions(utils.WithEntityCredentials(
      // Replace "<API-KEY-ID>" (including brackets) with your machine's API key ID
      "<API-KEY-ID>",
      utils.Credentials{
        Type:    utils.CredentialsTypeAPIKey,
        // Replace "<API-KEY>" (including brackets) with your machine's API key
        Payload: "<API-KEY>",
      })),
  )
  if err != nil {
    logger.Fatal(err)
  }

  defer machine.Close(context.Background())
  logger.Info("Resources:")
  logger.Info(machine.ResourceNames())


  // Instantiate the motor client
  motor1Component, err:= motor.FromRobot(machine, "motor-1")
  if err != nil {
    logger.Error(err)
    return
  }
  // Turn the motor at 35% power forwards
  err = motor1Component.SetPower(context.Background(), 0.35, nil)
  if err != nil {
    logger.Error(err)
    return
  }
  // Let the motor spin for 3 seconds
  time.Sleep(3 * time.Second)
  // Stop the motor
  err = motor1Component.Stop(context.Background(), nil)
  if err != nil {
    logger.Error(err)
    return
  }
}

Flutter code must be launched from inside a running Flutter application. To get started programming your machine with Flutter, follow the instructions to Build a Flutter App that Integrates with Viam. Then return to this page to add motor control to your app.

Add a new file to your application in /lib called motor_screen.dart. Paste this code into your file:

/// This is the MotorScreen, which allows us to control a [Motor].
/// This particular example uses both the Viam-provided [ViamMotorWidget],
/// while also providing an example of how you could create your own
/// widgets to control a resource.
library;

import 'package:flutter/material.dart';
import 'package:viam_sdk/viam_sdk.dart';
import 'package:viam_sdk/widgets.dart';

class MotorScreen extends StatelessWidget {
  final Motor motor;

  const MotorScreen(this.motor, {super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(motor.name)),
      body: Column(children: [
        // The first widget in our column will be the one provided
        // by the Viam SDK.
        ViamMotorWidget(motor: motor),
        const SizedBox(height: 10), // Padding between widgets

        // Here we have a button that controls the [Motor]:
        // Spin the motor at 35% power forwards for three seconds.
        // The [Motor] resource provides many control functions, but here
        // we are using the [Motor.setPower] method.
        //
        // You can extrapolate this to other Viam resources.
        // For example, you could make the onPressed function call
        // [Gripper.open] on a gripper, or [Sensor.readings] on a Sensor.
        Row(mainAxisAlignment: MainAxisAlignment.center, children: [
          ElevatedButton(
            onPressed: () async {
              motor.setPower(0.35); // Set motor power to 35%
              await Future.delayed(Duration(seconds: 3)); // Let the motor spin for 3 seconds
              await motor.stop(); // Stop the motor
            },
            style: ElevatedButton.styleFrom(
            minimumSize: Size(80, 20), // Adjusts width and height of the button
            padding: EdgeInsets.symmetric(horizontal: 4, vertical: 6), // Adjusts padding inside the button
          ),
            child: const Text('Set motor power', textAlign: TextAlign.center),
          ),
        ]),
      ]),
    );
  }
}

This code creates a screen with a power widget to adjust the power and a button that, when pressed, calls on the setPower() method to spin the motor forwards at 35% power, waits three seconds to let it spin, and then stops the motor.

Then, replace the contents of robot_screen.dart with the following file, or add the highlighted lines of code to your program in the locations indicated:

/// This is the screen that shows the resources available on a robot (or smart machine).
/// It takes in a Viam app client instance, as well as a robot client.
/// It then uses the Viam client instance to create a connection to that robot client.
/// Once the connection is established, you can view the resources available
/// and send commands to them.
library;

import 'package:flutter/material.dart';
import 'motor_screen.dart';
import 'package:viam_sdk/protos/app/app.dart';
import 'package:viam_sdk/viam_sdk.dart';

class RobotScreen extends StatefulWidget {
  final Viam _viam;
  final Robot robot;

  const RobotScreen(this._viam, this.robot, {super.key});

  @override
  State<RobotScreen> createState() => _RobotScreenState();
}

class _RobotScreenState extends State<RobotScreen> {
  /// Similar to previous screens, start with [_isLoading] to true.
  bool _isLoading = true;

  /// This is the [RobotClient], which allows you to access
  /// all the resources of a Viam Smart Machine.
  /// This differs from the [Robot] provided to us in the widget constructor
  /// in that the [RobotClient] contains a direct connection to the Smart Machine
  /// and its resources. The [Robot] object simply contains information about
  /// the Smart Machine, but is not actually connected to the machine itself.
  ///
  /// This is initialized late because it requires an asynchronous
  /// network call to establish the connection.
  late RobotClient client;

  @override
  void initState() {
    super.initState();
    // Call our own _initState method to initialize our state.
    _initState();
  }

  @override
  void dispose() {
    // You should always close the [RobotClient] to free up resources.
    // Calling [RobotClient.close] will clean up any tasks and
    // resources created by Viam.
    client.close();
    super.dispose();
  }

  /// This method will get called when the widget initializes its state.
  /// It exists outside the overridden [initState] function since it's async.
  Future<void> _initState() async {
    // Using the authenticated [Viam] the received as a parameter,
    // the app can obtain a connection to the Robot.
    // There is a helpful convenience method on the [Viam] instance for this.
    final robotClient = await widget._viam.getRobotClient(widget.robot);
    setState(() {
      client = robotClient;
      _isLoading = false;
    });
  }

  /// A computed variable that returns the available [ResourceName]s of
  /// this robot in an alphabetically sorted list.
  List<ResourceName> get _sortedResourceNames {
    return client.resourceNames..sort((a, b) => a.name.compareTo(b.name));
  }

  bool _isNavigable(ResourceName rn) {
    if (rn.subtype == Motor.subtype.resourceSubtype) {
      return true;
    }
    return false;
  }

  void _navigate(ResourceName rn) {
    if (rn.subtype == Motor.subtype.resourceSubtype) {
      final motor = Motor.fromRobot(client, rn.name);
      Navigator.of(context).push(MaterialPageRoute(builder: (_) => MotorScreen(motor)));
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(widget.robot.name)),
        body: _isLoading
            ? const Center(child: CircularProgressIndicator.adaptive())
            : ListView.builder(
                itemCount: client.resourceNames.length,
                itemBuilder: (_, index) {
                  final resourceName = _sortedResourceNames[index];
                  return ListTile(
                    title: Text(resourceName.name),
                    subtitle: Text(
                        '${resourceName.namespace}:${resourceName.type}:${resourceName.subtype}'),
                    onTap: () => _navigate(resourceName),
                    trailing: _isNavigable(resourceName) ? Icon(Icons.chevron_right) : SizedBox.shrink(),
                  );
                }));
  }
}

This imports the motor_screen.dart file into the program and adds logic to check if a resource is “navigable”, or, has a screen made for it. Since you added a screen for motor, motor is a navigable resource.

To navigate to the motor screen, save your code and launch your simulator. Navigate to the robot screen of your (live) machine with a motor resource configured, and see the resource control interface displayed:

You can adjust the toggle to change the power of your motor or press the buttons to make it revolve forwards and backwards.

package.json:

{
  "name": "test-rover",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "esbuild ./main.ts --bundle --outfile=static/main.js --servedir=static",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Viam Docs Team",
  "license": "ISC",
  "devDependencies": {
    "esbuild": "*"
  },
  "dependencies": {
    "@viamrobotics/sdk": "*"
  }
}

static/index.html:

<!doctype html>
<html>
  <head>
    <title>Drive a Rover</title>
    <link rel="icon" href="favicon.ico" />
  </head>
  <body>
    <div id="main">
      <button id="main-button" disabled="true">Click me</button>
    </div>
    <script type="module" src="main.js"></script>
  </body>
</html>

main.ts:

// This code must be run in a browser environment.

import * as VIAM from "@viamrobotics/sdk";

// This function gets the button element
function button() {
  return <HTMLButtonElement>document.getElementById("main-button");
}

const main = async () => {
  const host = "ADDRESS_FROM_VIAM_APP";

  const machine = await VIAM.createRobotClient({
    host,
    credential: {
      type: "api-key",
      // Replace "<API-KEY>" (including brackets) with your machine's API key
      payload: "<API-KEY>",
    },
    // Replace "<API-KEY-ID>" (including brackets) with your machine's API key ID
    authEntity: "<API-KEY-ID>",
    signalingAddress: "https://app.viam.com:443",
  });

  button().onclick = async () => {
    // Instantiate the motor client
    // Replace with the name of a motor on your machine.
    const name = "motor-1";
    const motorClient = new VIAM.MotorClient(machine, name);

    // Turn the motor at 35% power forwards
    await motorClient.setPower(0.35);
    // Let the motor spin for 3 seconds, then stop the motor
    const sleep = (ms: number) =>
      new Promise((resolve) => setTimeout(resolve, ms));
    await sleep(3000);
    await motorClient.stop();
  };
  button().disabled = false;
};

main().catch((error) => {
  console.error("encountered an error:", error);
});

#include <boost/optional.hpp>
#include <string>
#include <vector>
#include <unistd.h>
#include <viam/sdk/robot/client.hpp>
#include <viam/sdk/components/motor.hpp>

using namespace viam::sdk;

int main() {
    std::string host("muddy-snow-main.7kp7y4p393.viam.cloud");
    DialOptions dial_opts;
    dial_opts.set_entity(std::string("<API-KEY-ID>"));
    /* Replace "<API-KEY-ID>" (including brackets) with your machine's api key id */
    Credentials credentials("api-key", "<API-KEY>");
    /* Replace "<API-KEY>" (including brackets) with your machine's api key */
    dial_opts.set_credentials(credentials);
    boost::optional<DialOptions> opts(dial_opts);
    Options options(0, opts);

    auto machine = RobotClient::at_address(host, options);

    std::cout << "Resources:\n";
    for (const Name& resource : machine->resource_names()) {
        std::cout << "\t" << resource << "\n";
    }

    std::string motor_name("motor-1");

    std::cout << "Getting motor: " << motor_name << std::endl;
    std::shared_ptr<Motor> motor;
    try {
        // Get the motor client
        motor = machine->resource_by_name<Motor>(motor_name);
        // Turn the motor at 35% power forwards
        motor->set_power(0.35);
        // Let the motor spin for 3 seconds
        sleep(3);
        // Stop the motor
        motor->stop();
    } catch (const std::exception& e) {
        std::cerr << "Failed to find " << motor_name << ". Exiting." << std::endl;
        throw;
    }
    return EXIT_SUCCESS;
}