pxt-ev3/docs/tutorials/city-shaper/robot-2.md

# Robot 2 Lesson

## Step 1 - Build Your Driving Base Robot @unplugged

Build the robot driving base:

[![EV3 Driving Base](/static/lessons/common/ev3-driving-base.jpg)](https://le-www-live-s.legocdn.com/sc/media/lessons/mindstorms-ev3/building-instructions/ev3-rem-driving-base-79bebfc16bd491186ea9c9069842155e.pdf)

If clicking on the image above doesn't open the instructions, right-click on the image and choose "Save link as..." to download the PDF.

## Step 2 - Show an image and move @fullscreen

Add blocks to the ``||loops:on start||`` block to show an image and move the motors **B+C** for ``1`` rotation.

```blocks
brick.showMood(moods.neutral)
motors.largeBC.steer(0, 50, 1, MoveUnit.Rotations)
```

## Step 3 - Brick button @fullscreen

Let's change the code so that your robot moves when the **UP** button is pressed.
Add an ``||brick:on button up||`` block and move ``||motors:steer motors||`` inside of it.
After downloading your code, press **UP** to move the robot.

```blocks
brick.buttonUp.onEvent(ButtonEvent.Pressed, function () {
    brick.showMood(moods.awake)
    motors.largeBC.steer(0, 50, 1, MoveUnit.Rotations)
})
brick.showMood(moods.neutral)
```

## Step 4 - Braking @fullscreen

When the motors are done turning, the robot keeps on moving for a short distance. 
Turn on the **brakes** so that your robot stops immediately.
Drag a ``||motors:set brake||`` block into the ``||loops:on start||`` and set it to **ON** for the the **BC** motors.

```blocks
brick.buttonUp.onEvent(ButtonEvent.Pressed, function () {
    brick.showMood(moods.awake)
    motors.largeBC.steer(0, 50, 1, MoveUnit.Rotations)
})
brick.showMood(moods.neutral)
motors.largeBC.setBrake(true)
```

## Step 5 - Left and Right turn @fullscreen

Let's make the robot turn to the left when the **LEFT** button is pressed on the brick.
Find an ``||brick:on button||`` block and put a ``||motors:steer motors||`` in it. Make the turn ratio drive the motor to left.
Get another ``||brick:on button||`` and set it to run when the **RIGHT** is pressed.
Put a ``||motors:steer motors||`` in for that button and set the turn ratio to drive to the right.

```blocks
brick.buttonLeft.onEvent(ButtonEvent.Pressed, function () {
    brick.showMood(moods.middleLeft)
    motors.largeBC.steer(-50, 50, 1, MoveUnit.Rotations)
})
brick.buttonRight.onEvent(ButtonEvent.Pressed, function () {
    brick.showMood(moods.middleRight)
    motors.largeBC.steer(50, 50, 1, MoveUnit.Rotations)
})
```

## Step 6 - Backwards @fullscreen

Let's make the robot go backwards when the **DOWN** button is pressed on the brick.
Add a ``||motors:steer motors||`` to an ``||brick:on button||`` block and change the speed to be negative. This will make the motor go backwards.

```blocks
brick.buttonDown.onEvent(ButtonEvent.Pressed, function () {
    brick.showMood(moods.knockedOut)
    motors.largeBC.steer(0, -50, 1, MoveUnit.Rotations)
})
```

## Step 7 - Add an Ultrasonic sensor @fullscreen

Add an Ultrasonic sensor to your driving base.

[![EV3 Driving Base with Ultrasonic Sensor](/static/lessons/common/ev3-ultrasonic-sensor-driving-base.jpg)](https://le-www-live-s.legocdn.com/sc/media/lessons/mindstorms-ev3/building-instructions/ev3-ultrasonic-sensor-driving-base-61ffdfa461aee2470b8ddbeab16e2070.pdf)

If clicking on the image above doesn't open the instructions, right-click on the image and choose "Save link as..." to download the PDF.

## Step 8 - Stopping distance @fullscreen

Create a program that moves the Driving Base and makes it stop 6 cm from the Cuboid.

```blocks
brick.buttonEnter.onEvent(ButtonEvent.Pressed, function () {
    brick.showMood(moods.dizzy)
    motors.largeBC.steer(0, 50)
    pauseUntil(() => sensors.ultrasonic4.distance() < 6)
    motors.largeBC.stop()
})
```

Try sending your robot towards a wall!