The control user interface can be created with the Blynk app builder using four button controllers to move the robot forward, backward, left, and right:

1. Open the Blynk app builder and tap New Project:

2. In the Create New Project page, type in the project name, Robot Car. Under CHOOSE DEVICE, select the correct Raspberry Pi model. Then, under CONNECTION TYPE, select WiFi. If you're using a Raspberry Pi model 1 or 2, you should connect an external Wi-Fi dongle to the Raspberry Pi's USB port. The Raspberry Pi model 3 has a built-in Wi-Fi module, so you don't need to connect a Wi-Fi dongle to it. Finally, tap Create to build the project workspace:

3. Tap the OK button:

4. In the project workspace, tap the plus icon to open the Widget Box and add four buttons:

5. Then, arrange the buttons as shown in the following screenshot:

• • Configure the buttons as follows:
    • FORWARD: Virtual pin V0
    • BACKWARD: Virtual pin V3
    • LEFT: Virtual pin V1
    • RIGHT: Virtual pin V2

6. Once configured, the buttons should look like this:

7. Now, you have successfully built the controller interface. The left and right buttons can be used to turn the robot forward left and forward right. You will use the swing turn mechanism to turn the robot to either direction:

• • Forward left swing turn: Turn off the left motor, drive the right motor forward:

• • Forward right swing turn: Turn off the right motor, drive the left motor forward: