Using MicroBlocks with MIT App Inventor
Imagine what you might do with mobile apps that interact with the physical world. You might control a robotic dog or a spooky Halloween light display from your phone. Or an app might tell you when your house plants were getting thirsty and let you water them with the click of a button.
Projects like these are easy to create with MicroBlocks and the new MicroBlocks extension for MIT App Inventor.
MIT App Inventor is a free, blocks programming language that makes it easy to create mobile apps for Android phones and tablets. (The App Inventor team is working to add iOS support as well. However, at the moment, the MicroBlocks extension works only with Android devices.)
The key to making mobile apps that interact with the physical world is the new MicroBlocks MIT App Inventor extension, which uses Bluetooth Low Energy (BLE) to communicate between an Android mobile device and BLE-capable MicroBlocks boards such as the micro:bit V2.
Implementing such apps requires creating both an App Inventor project and a MicroBlocks project. Fortunately, it doesn't take much code to do cool things, and it is easy to get started. If you are already familiar either MIT App Inventor or MicroBlocks, you're already halfway there!
MicroBlocks Hello Purr
MicroBlocks Hello Purr is a simple demo application created by Natalie Lao from the App Inventor Foundation. It allows you to send purr messages between your mobile device and a micro:bit V2. Although this application requires very little code, it demonstrates the three key elements of every MicroBlocks/App Inventor project: making a Bluetooth (BLE) connection, sending messages, and handling incoming messages.
MicroBlocks Scripts
The MicroBlocks side contains three scripts:
The startup script displays an image (a line of LED's) on the LED display to show that it is running.
Pressing the A button sends the message PET to App Inventor. It also scrolls the word Purr as feedback.
The third script runs when MicroBlocks receives the petted message from App Inventor. It displays a cat face and uses the tone block in two for loops to create a purr sound.
You can make MicroBlocks respond to more messages by adding additional when _ received blocks.
App Inventor Scripts
The App Inventor side has four scripts. The first two are used to initiate a BLE connection when the connect button is pressed and to turn the button green to provide feedback that a connection has been made:
The connection is made by name. MicroBlocks boards have names like MicroBlocks XYZ, where the last three letters identify the board. Your micro:bit will flash its three-letter code when it is reset or powered up. When using the app, you'll need to change the last three letters of the board name in the input box to your board's three-letter code using capital letters.
[Note: If your board is based on a Raspberry Pi Pico-W, then it's name will start with the word "Pico" instead of "MicroBlocks". Technical limitations of the BLE support on the Pico-W limits the length of board names to eight characters.]
The other two App Inventor scripts handle sending and receving messages:
Clicking the cat picture sends the message petted to MicroBlocks.
Receiving the message PET from MicroBlocks plays a purr sound on the mobile device.
You can probably see how to extend this App Inventor project by adding buttons to send additional messages. To handle additional incoming messages, you just need to add an if block for each message.
Complete Programs
Download the complete programs to try this yourself.
App Inventor: MicroBlocksHelloPurr.aia
MicroBlocks: MicroblocksHelloPurr.ubp
Resources
App Inventor
MicroBlocks
App Inventor MicroBlocks BLE Extension
MicroBlocks Extension Documentation