LEGO has helpfully given us an app that can operate every aspect of your EV3 robots. It can control motors, both large and medium. It can give you a joystick or slider bars to control motors singly or in combination. It can also report the status of your sensors. This is exceptionally useful for testing a new design without writing any software.
Downloading and Running the Robot Commander App
Figure B-1 shows a screenshot from the LEGO Robot Commander app download page. As shown at the bottom, you can download the Android version from Google Play, or the iPhone version from the App Store. These downloads are free.
Figure B-1. A screenshot from the LEGO Robot Commander download page. Two configuration screens are seen in this view.
The app comes with pre-configured controls for the five Kit Robots shown on the box with the EV3 Retail Kit. However, for our purposes, we want to be able to create custom command screens for the robots in this book, or others you may build.
Figure B-1 shows two possible user-configured control screens. The center smartphone screenshot demonstrates how you can position the control elements anywhere on the smartphone screen. In this case, a dual motor control is at the upper left, and a slide bar is below that. The dual-motor control would typically operate both large motors, possibly as regular wheels, a tracked vehicle, etc. The slide bar would then operate the medium motor, say as a gripper jaw as seen with the PushBot.
The Perfect Hardware-Testing App
The Robot Commander app played an important role in the design of the PushBot. In Figure B-2, we see the PushBot from the Grabber Jaw end. This design “looks good”—that is, it should be able to close the jaw on a Mayan Figurine (or a bottle of water). And the bottle should be able to fit nicely in the jaws. And the bot should be able to push the bottle on to a pressure plate.
Figure B-2. The PushBot after being tested and hardware-validated with the Robot Commander app
But will it? When you do this kind of testing, the Robot Commander app is (you guessed it) your friend. As you design a bot, you can test it as soon as your motors are fastened and wired up. You configure the app with controls and try it! First, create a joystick for the drive motors and a slide bar for the Grabber Jaw. Then turn Bluetooth on for your bot. Synch them up and the app is in control.
I tried a few different hardware design tweaks for the PushBot. I tested each one (drive, grab, push, release, back up) and made hardware improvements each time. And the design you see in Figure B-2 works great. At that point, I sat down and began working on the actual downloadable software as described in Chapter 20. I knew the hardware would work if the software were designed correctly.
Engineering: Isolating Design Issues in Testing
And now for our final Engineering sidebar. The Robot Commander offers us a valuable service in design and testing. If we simply built the PushBot and downloaded software to run it, we’d probably find something not working. And we might have to puzzle out whether the problem was hardware or software. But the Robot Commander has isolated the hardware from the software. So we can build a bot that should work and verify the hardware before writing any software.
So if something doesn’t work in software testing, we can dig into the software problem with confidence the hardware is okay. After all, remember all those times we said “The hardware should work?” Well, we saw it work! And the Robot Commander app was the key to that testing.