GUI Layout

My Golden Rules:

• Design your GUI thoroughly on paper first and keep it as simple as possible (KISS).
• Set Sizing to Responsive (Project Properties Button)
• Set Screen Align Horizontal to Center: 3
• Set Screen Align Vertical to Top: 1
• Always use Arrangements (aka Containers) for the small components (buttons labels etc)
• Define Arrangement and Component widths in %
• Tip - Set Arrangement widths at max 98% because with some phones that is the max the User gets to see
• Set Horizontal Arrangements Alignment to Horz Center, Vert Center
• Set Vertical Arrangements Alignment to Horz Center, Vert Top
• Tip - when inserting components, size their width to 20pix initially so you can fit them all in easily, then modify them to final size
• Tip - Inserting components is also easier to do with Preview set to Tablet
• Tip - Use empty Labels as spacers between components, typically 1%, with no margin and text/back colour set to none.
• When using Horizontal Arrangements, make the components height a little less (1 or 2%) than the Arrangement to separate Components vertically
• Buttons must to be FFF (fat finger friendly) - make them wide and high (12% high Horizontal Arrangement with 10% high buttons works well)
• Tip - Image Buttons can save screen space and, cleverly defined, can be effectively understood by all
• Give every component a meaningful name - but always retain the component type name e.g. Label_PickedValue_Scrn01, Button_CalcTotal_Scrn01
• The Designer View and Emulator are approximations - test your GUI design early with as many devices as possible

• Optimise all images
• Optimise all code (using 'Any Component' events instead of individual event Blocks)
• Test and Test again
• DRY - Don't Repeat Yourself
• Keep it Lean and Mean
• Keep It Simple Stupid

KISS, an acronym for Keep It Simple, Stupid, is a design principle noted by the U.S. Navy in 1960. The KISS principle states that most systems work best if they are kept simple rather than made complicated; therefore, simplicity should be a key goal in design, and unnecessary complexity should be avoided.

  KISS Explained  YouTube Movie: Professorcad is not associated with advertisements that may accompany the movie!

Note that if deploying image buttons, especially for toolbars, they may have to be defined in pixels (height and width) to minimise distortion. In my experience, square buttons 50pix x 50pix (min 44pix x 44pix) can serve a range of different phone sizes. A Horizontal Scroll Arrangement (aka container) can ensure the User has access to all of the buttons on the toolbar. You can use smaller buttons, but space them apart so your Users do not hit the wrong one!

  Simple GUI How To Movie

With the HTML option selected, You can use HTML tags in Label Components

HTML Tags Supported

Images

Defined and or managed incorrectly, images will take up too much memory and could cause a crash:

• Do not link Public Images directly into your app. Wikipedia for example changes frequently and images are changed or lost
• Ensure that you have the Rights necessary to use your chosen images in your app
• Some images may need to be paid for, others require recognition in your app. If in doubt, choose from elsewhere
• Reduce the dimensions (height, width) of each image so that they are at the size they will be in the App GUI, or very slightly larger
• Reduce the colour depth of each image as appropriate:
  Transparent: 32bit; No Transparency: 24bit; Drawings: have less colours and can normally be reduced to 16bit
• Use the WebP format for highest image quality, good scaling and small file sizes (approximately 25% smaller than PNG, JPG)
• Save all images as zero compression. This removes the task of decompression when the app/image is loaded (= faster App)
• Make the image file for the App icon 96pix x 96pix zero compression PNG (WebP not yet supported). NOTE: Do not use other formats like WebP, JPG or BMP
• File Naming: It is a good idea to give all files meaningful names, but not longer than 32 characters (including the extension), less if possible (approximately 20 character names fit in AppInventor Property boxes). Do not use special characters!
• All of this image pre-app enhancement can be done on your computer with almost any image software
  My favourite is IrfanView IrfanView

App Icon Exception: Adaptive icons: Specify an app icon 512 x 512 pixels PNG format and the App Inventor Build Server will generate icons for every available icon size and shape needed for Android

Cannot Build or Install APK, or APP installs but Crashes/Freezes  

Things to look out for:

• The Project has gone beyond the maximum size of 30MB
• The Project has gone beyond the maximum recommended 10 screens
• The Project has a Text Block containing an excessive amount of text
• The Project has an ASCII Null character within a text string
• One or more Screen Names contain an underscore '_' character - use letters and numbers only
• The icon file is not a PNG or is too large (use 96pix x 96pix zero compression PNG)
• App Icon Exception: Adaptive icons: Specify an app icon 512 x 512 pixels zero compression PNG format. The App Inventor Server will generate icons for every valid icon size and shape for Android
• The Project has images that have not been optimised for Android Optimise Images for Android
• Project, Screen, Block, Procedure Component or Asset Name is a Java or Scheme keyword Java and Scheme Key Words
• There are Blocks with missing Pieces (look out for warnings)

• The Project has an excessive amount of Blocks and/or Components
• The Blocks include excessively long logic computations
• The Blocks include excessively long text operations
• Virtually the same Blocks/Components are repeated many times. Examples: Many Screens when just two or three would be perfect with better code; Many Labels or TextBoxes when a single ListView would be better.
• The Project file has some form of corruption
• The Project file name includes an unsupported character
• The Build process is being interrupted by an Anti-Virus application (can cause corrupted files)
• A Procedure has not been given a Unique Name
• The Project is using an incompatible or out of date Extension (Check with the Extension Developer)
• The Project has been saved with a non App Inventor IDE, making it incompatible
• The Browser is not supported -use FireFox, Chrome or Safari (latest versions)
• The Internet Connection is not optimal
• The Network FireWall is blocking App Inventor

• The Target Device (e.g. Smart Phone) does not have the 'Allow Apps from Unknown Sources' Security Permission set - go to Settings/Apps/Unknown Sources
• The APK has been built for a higher Android version than the version on the Target Device
• If the App Installed before, try uninstalling the old version first
• There is not enough memory available to instal the App ('App not Installed' error message): Delete any Apps that are no longer required to free-up space
• The APK was not fully saved on the Target Device when transfered via WiFi. Try saving to your PC instead and move it to the Device via a USB cable ('adb' install)
• The APK name contains a non-printing character: If the name was copied and pasted into App Inventor, something like a carriage return or tab character could be in it
• The APK file is corrupt. This could have happened during it's 'journey' to the device. Since you made the App and know it is not Malicious, try disabling the Security Measure 'Verify Apps'
• The Device is running a Screen Filtering App such as Twilight, f.lux, CF.Lumen - any that offer a blue light filter - disable that App, try again to install yours
• The Device is running an App that has the ability to overlay other Apps (often found on Samsung Devices) - disable that App, try again to install yours
• The Device does not have suffient storage for another App to be added or the App is larger than Android will allow
• The Device does not have suffient memory (RAM) to run the App. This could be caused by too many other Apps running in the background
• The App is an Update of an existing App but does not have the same credentials - key or certificate
• A recent update of Android on the Device has caused an App Installation issue - a Google Search should reveal any issues
• The Device System User Interface cache has grown too large - go to Settings/Apps/All and select 'System UI'. Wipe the cache and restart the Device.
• The Device Downloads Manager cache might be corrupted - go to Settings/Apps/All and select 'Downloads Manager'. Wipe the cache and restart the Device.
• Cannot find the APK on the device! The best place to put an APK is in the Downloads Folder. There should be an icon on your screen for the 'File Manager' - navigate to and install the APK via that icon
• I am installing an APK to test and debug: Enable Developer-Debug mode on the device Set Developer Mode

• The App runs OK for a while, then freezes or crashes: Memory issue: If using multiple Screens, ensure each Screen is closed when switching to another Screen
• The App runs OK for a while, then freezes or crashes: Memory issue: If using images, ensure the dimensions and byte size is as small as possible: Tips Images
• The App runs OK for a while, then freezes or crashes: Memory issue: If using Clock Timers, ensure they are disabled when switching to another Screen

• The App runs OK for a while, then freezes or crashes: Memory issue: If using Clock Timers, ensure they have an adequate time duration to complete the process before being called again
• The App runs OK for a while, then freezes or crashes: Memory issue: If using Clock Timers, ensure they are only enabled when required. It is common practice to disable within the Timer Block itself
• The App runs OK for a while, then freezes or crashes: Memory issue: Check your code for a never-ending loop (For Loop, While Loop)
• The App runs OK for a while, then freezes or crashes: Memory issue: Check that your device actually has enough memory to run your App (Delete Apps you no longer use)
• The App runs OK but there is unexpected behaviour: This could be caused by a myriad of things, most likely a bug in your code Blocks.
  Ensure you are using the correct Block types - for example, only use the Text Compare Block to compare Text!
• The App runs OK for a while but then halts with an Error Message: You can catch such errors with the Screen Error Occured Block. How to use the Block effectively: Free code: Get Error Info

MIME TYPES

Used by the Storage Access Framework (aka SAF), emails, Web Apps/Servers

Iana: Internet Assigned Numbers Authority: Registration of Media MIME Types

MOCK DATA FILES

Download files for App Testing [Public Domain Free To Use]

BLOCK LISTS TEMPLATE

Download an App Inventor File which consists of Block Lists for Text, Numbers, Images, Buttons, Labels and TextBoxes of 10, 20, 30 and 40 rows. Keep it in App Inventor with your Projects and simply copy the List you require to the Backpack. [Public Domain Free To Use]

Project File Care  

"Good Housekeeping" pays dividends!

• Save Backups of your Project to your computer hard drive frequently

• Give Screens, Components and Blocks meaningful names
• Keep Screen1 as the "King" or "Main" Screen
• Retain the Component Type name when naming a component e.g. TextBox_UserInputName_Scrn01
• Take care not to use a Java or Scheme keyword as a Project, Screen, Block, Procedure or Component Name
• Arrange Blocks in one vertical column by right-clicking in the WorkSpace and selecting "Cleanup Blocks"
• Comment your code! Easiest way is to recycle a global variable

• Do not leave empty jigsaw pieces - unexpected results can occure when testing/compiling

• Empty the BackPack as soon as the contents are no longer required
• Let App Inventor be the King of the Browser - do not have umpteen other websites open at the same time
• Do not ignore any error messages or warnings - deal with them immediately

Getting Help on the App Inventor Forum  

An average of 1 million Users per month means that you have a lot of competition for the attention of the Power Users (Technical Support Volunteers). Therefore, it is in your best interests to ensure that your help request is very carefully described and where appropriate supported with images and a small Test Project File (.aia) that demonstrates the problem.

If you are communicating with (IOT) hardware such as Arduino, BBC Microbit, Raspberry Pi, Banana Pi -include your Sketch/Script and connectivity (BlueTooth, BlueTooth LE [BLE], WiFi, Serial/USB Serial). Include your schematic or circuit diagram too.

If you are having trouble with App Inventor (rather than your work on your App) try this first: MIT: Troubleshooting for App Inventor 2

The Basics

• Search the Forum - somebody somewhere has most likely asked the same question already
• Do a Google Search - somebody might have answered your question in a different forum, blog or YouTube video
• Ensure you create a Topic in the correct section of the Forum
• Strictly one Topic per question and one question per Topic
• Note that if new to the Forum, the number of posts you can make in your Topic is limited, so make sure your information is really informative!
• Do not try to "bump" your Topic or title it as "Urgent". Everybody's project is urgent!
• Make your Topic Title descriptive. "Help", "How do I do this?" and similar titles do not draw the Power Users to your problem
• Keep the subject on the forum. It is not acceptable to email to Power Users directly.
  By keeping the discussion on the forum, there are many people from all around the World (different time zones) who can potentially help you, not just the first responder, who may be unavailable. Plus, there is often something that many forum members can learn by reading the posts.

Description: Tell Us:

• What is the purpose of your App?
• What is the purpose of the problem code, what should it do?
• What have you tried?
• How have you tested the code (e.g. App Inventor Emulator on PC, AI Companion on Android Device, Debug APK on Android Device)
• Manufacturer and Model of your Android Device
• What is the exact Android version on your Test Device?
• Does your code use an Extension? If so, include Extension Name and Developer Name

How to insert an image of your Blocks into your Forum Post

Forum Etiquette

• Be polite at all times. Nobody wants to help people who are rude! Note that WRITING IN CAPITALS is interpreted as shouting
• Please do not ever use bad language, many forum members are very young
• External Links: Please do not link to political, religious, pornographic or other potentially controversial websites
• Disparaging remarks or any form of discrimination are not welcome - App Inventor is for everyone
• The Power Users are unpaid volunteers who have considerable programming experience - their time is precious, please do not waste it.
• Please do not send emails directly to the Power Users. By keeping the discussion on the forum, there are many people from all around the World (different time zones) who can potentially help you, not just the first responder, who may be unavailable. Plus, there is often something that many forum members can learn by reading the posts.

MIT: App Inventor Forum Posting Guidelines

Android Versions

Android Permissions

Please note that some of these permissions cannot be used or can no longer be used

General

MIT: Setting Up App Inventor
MIT: Updating App Inventor Setup Software
MIT Library: Documentation & Support
MIT: User Interface Components
MIT Library: Live Development, Testing and Debugging
PDF: Franklyn Turbak: PDF: 🔥 Events-First Programming In App Inventor
PDF: CCSCNE14: PDF: 🔥 Presentation re Events-First Programming In App Inventor
Oracle: Date and Time Patterns [Used with the App Inventor Clock Component]
Power User TimAI2: Metricat AI2: 🔥 Introduction to App Inventor plus excellent Scraps, Guides and Resources
Power User Juan Antonio: 🔥 Introduction to App Inventor, Arduino and other microcontrollers, Guides, Resources, Tutorials
Power User Taifun: 🔥 App Inventor Tutorials, Code Snippets and Extensions.
Power User SunnyTheDeveloper: 🔥 App Inventor Extensions.

Trouble Shooting your App Inventor Setup

MIT: Setting Up App Inventor
MIT: How to Update the App Inventor Setup Software
MIT:App Inventor Online Connection Test
MIT: IT Help for Schools using MIT App Inventor
MIT:Connecting your Phone or Tablet over WiFi

Report Anti Virus Potential False-Positive

Ahn Lab
Avast
AVG
Bit Defender
Malwarebytes (via their forum)
Eset
Kaspersky
McAfee
Sophos
Norton-Symantec
Trend Micro

Test your Android App .apk or Windows Desktop Program .exe with all Anti-Virus software online, with one upload

Virus Total

Alternative Stores you can upload your App to (Google Play is not the only App Store!)

Huawei App Store (huge)
SlideME Marketplace
Amazon
Samsung App Store
mobile9 App Store
Bemobi - associated with Opera
Mobango
Get Jar
CNET
Torrapk
Apk Pure
Market Place Zoom
Aptoide
Softonic
Product Hunt (App hosted on your own website)
Mobile Toones

Publish Your App On Google Play Store  

🔥 Hot Tip: To update your App on the Play Store:

• Use the same Google Account as you did for the original App, to both develop your App Update and upload to Google Play Store
• Using your original Project File as the base for the Update ensures the use of the same Keystore as the original
• Ensure you update the App Version Code and App Version Name in Screen1 properties

Note: App Inventor Apps now require an Android App Bundle for Google Play Store. Other Stores may require either an App Bundle (AAB) or an APK. App Inventor can build both.

MIT: Uploading your Apps to Google Play Store
App Inventor Forum: Tutorials and Guides: Publish App On Google Play Store (27/01/2021)
GoodFirms Blog: Anastasiya Filiuta: How to Publish an Android App on Google Play Store (25/09/2022)
Google: Google Play Launch Check List
Google: Google Play Developer Policy Center
Google: Play Console Help
Google Console for Google Play Store (signup)
Summary of Android Manifest Permissions
Coding Minds: 📽 YouTube: How to Publish Your MIT App Inventor App to Google Play [25/07/2017]
Mariusz Ferdyn: 📽 YouTube: How to publish App Inventor application to Google Play [29/04/2018]

🔥 Hot Tip: How to delete your App from the Play Store:

Google Play Account

• Go to your Google Play account and log in.
• Click on the application you want to delete.
• Click on the Store Presence menu, and click on "Pricing and Distribution".
• Click on Unpublish

Learning App Inventor

📽 MIT Beginner Videos hosted on Vimeo
🔥 MIT Book 2 Free online PDFs or purchase the book and help fund App Inventor
Books about App Inventor that you can buy online or in your local bookstore
Course In A box
MIT Tutorials
Kumaraswamy: 🔥 App Inventor & Javascript: Helpful things you need to know
Sajal Dutta: App Inventor Blocks
Professor Wolber: App Inventor Tutorials
Metricat AI2: Introduction to App Inventor plus excellent Scraps, Guides and Resources

App Inventor & JSON (JavaScript Object Notation) Data

Official JSON Website: Introducing JSON
Official JSON Website: JSON Example
📽 MIT Video: Evan Patton: 🔥 How to work with Lists, Dictionaries and web services using JSON
FoYo: Decoding JSON with Dictionary Blocks
Abraham Getzler: 🔥 How to decode quiz JSON from opentdb.com (includes Example Project)
Free online source of quiz questions
Mozilla: MDN Web Docs: Working with JSON

App Inventor for Teachers

App Inventor for Educators
App Inventor Forum for Teachers: Educational Issues
App Inventor Forum: App Inventor Instructors
Teaching with App Inventor
Teaching App Creation with MIT App Inventor
MIT App Inventor Teaching Modules
App Inventor Starter Curricula
Metricat AI2: 🔥 Introduction to App Inventor plus excellent Scraps, Guides and Resources

External Storage

An easy way to exchange files between your Smartphone and your PC is via eMail!

MIT: 📽 Using Google Sheets in MIT App Inventor
Metricrat: App Inventor: 🔥 Post Data to Google Sheet
MIT:How to work with Fusion tables
MIT:Cloud DB
MIT: Firebase DB
Derek Banas: 🔥 MySQL DB

App Security

comparitech: Flawed credential storage in top Android apps puts users at risk

Activity Starter

MIT: Using the Activity Starter
Activity Starter Examples
Alex Fuentes: 📽 YouTube: MIT App Inventor 2 Activity Starter
Andy Havranek: 📽 YouTube: App Inventor 2 Activity Starter YouTube Link Tutorial
MIT:App Inventor2 Book: Chapter 6: launching other Android Apps from your App

Arduino, other Microcontrollers and Related Subjects including Bluetooth and other Wireless Technologies  

Arduino ESP8266 WiFi Module ESP32 WiFi & Bluetooth Mini Microcontroller LinkIt BBC micro:bit PIC Raspberry Pi 8051 microcontroller (Intel MCS-51) Bluetooth Wireless Technologies Robots Nordic Thingy 52 STM 32 BlueFruit LE

Arduino    Back 

🔥 Hot Tip: Ardunio Sketch (Script): Use Serial.println() (empty!) to separate messages when you transmit.
App Inventor: Set DelimiterByte to 10 in the BlueTooth Block.
Check that: Bytes Available > 0 in BlueTooth Block.
Then request -1 bytes to get the full message data.

🔥 Hot Tip:  Official Arduino Website Forum: Arduino Nano 33 BLE Bootloader corruption fix (may be viable for other boards too)

Specification of an AC To DC Power Adaptor For Arduino UNO: 9v to 12V max DC output, 250mA to 1A max current output, 2.1mm diameter plug which is centre pin positive. If you are connecting kit like lots of LEDs, LCDs, servo motors etc, the Adapter should supply at least 500mA, upto 1A max.

[01] Official Arduino Website: Home
[02] Official Arduino Website: Programing Language Reference
[03] 🔥 Arduino Basics Tutorial Blog (massive site, tons of info)
[04] Open Source Hardware Group Arduino Tutorials: 📽 YouTube: How to Use and Understand the Arduino Reference
[05] Afrotechmods: 📽 YouTube: You can learn Arduino in 15 minutes
[06] Tinker CAD: Circuits: Simulate your Arduino Circuit and Sketch Code online
[07] Programming Electronics Academy: 📽 YouTube: Tinker CAD: Arduino Simulator demonstration
[08] Arduino Tutorial: Learn Electronics using Arduino (not using App Inventor but a useful Arduino tutorial)
[09] MIT: IoT: Introduction:Ardunio 101 (Note: other Ardunio boards are similar)
[10] 🔥 Random Nerd Tutorials: Arduino Trouble-shooting Guide
[11] Instructables: Arduino Home Automation
[12] CODEDUINO: Arduino Projects, Tutorials and News
[13] Instructables: Controlling a Servo With an Arduino 101
[14] Muhamad Andi Prasetyo: 📽 Video Tutorial: App Inventor 2: Android Receive Data from Arduino via Bluetooth
[15] 🔥 Random Nerd Tutorials: Rui Santos: Android Apps for Arduino with MIT App Inventor 2
[16] Random Nerd Tutorials: Rui Santos: Arduino Step-by-step Projects: Build 25 Projects
[17] 🔥 Arduino-er: How to read service UUID and Characteristic of HM-10 BLE Module, using AT command
[18] 🔥 Design Spark: Arduino Stepper Motor Control
[19] Becky's IoT Class: communicate with the ESP8266 and Arduino. Note: does not include App Inventor but if you want to know all about the ESP8266, very informative
[20] Hackster: MisterBotBreak: How to Debute Arduino with LED (Beginner Introduction without using App Inventor)
[21] Everything ESP: ESP32 Arduino Tutorial: Alarm with PIR motion sensor and buzzer
[22] 🔥 Juan Antonio: BLE ESP32 Bluetooth Send Receive Arduino to-from Inventor App
[23] 🔥 Juan Antonio: Bluetooth HC-06 Send and Receive Arduino to-from App Inventor App. Send Text File. Send Image.
[24] 🔥 Martyn Currey: Arduino, HM-10 BLE Module and App Inventor 2
[25] Arduino: Send SMS
[26] MIT: App Inventor: 📽 Video: Send Arduino sensor data to Website
[27] DFROBOT Bluno: An Arduino Uno specification board with built-in BLE
[28] Zaki Zakaria: Controlling a Servo: MIT App Inventor and Arduino via Classic Bluetooth
[29] 🔥 Simon Monk: Learn Arduino: 18 Arduino Lessons. ** Highly recommended - fun and very informative, as are Simon's books. **
[30] Arduino Project Hub: Pulse Width Modulation Tutorial (brightness of LED example)
[31] Arduino Project Hub: Getting Started with HC05 Bluetooth Module (includes wiring diagram)
[32] Electro Peak: Educational and Fun: Arduino Projects
[33] Cool Components: Fixing Common Arduino Issues
[34] Programming Electronics Academy: 📽 YouTube Channel: Learn Programming and Electronics with Arduino
[35] Maker Pro: How to Control Servo Motors from a Mobile Device with an Arduino UNO and an Android App
[36] 🔥 STEM Education: 📽 YouTube: App Inventor 2 to Control an Arduino Robot
[37] 🔥 Circuit Digest: 📽 Servo Motor Control using Arduino (includes Video)
[38] Instructables: Setting Up Bluetooth HC-05 With Arduino
[39] 🔥 Juan Antonio: Arduino and other microcontrollers, Guides, Resources, Tutorials
[40] 🔥 Arduino Docs: Nano 33 BLE Sense Cheat Sheet
[41] 🔥 Predictable Designs: John Teel: 📽 YouTube: Arduino in a commercial product?
[42] 🔥 cactus.io: Arduino UNO R3

Atmel ATtiny85/ATtiny84 (Atmel is part of Microchip Tech)    Back 

Official ATtiny85 Website
Hackster: Robin Thomas: ATtiny85/84 micro controller with Bluetooth

ESP8266 WiFi Module    Back 

🔥 Hot Tip: The ESP8266 ESP-01 WiFi Module can be used with or without a companion microcontroller. It is an SOC - System On a Chip.

[01] ESP8266 Community Forum
[02] Instructables: Getting-Started-With-the-ESP8266-ESP-01
[03] Instructables: How to use the ESP8266-01 Pins and LEDs
[04] Techiesms: 📽 Video: How to Program a ESP8266-01 using the Arduino IDE
[05] EEVblog: 📽 Video: How to connect and use the low cost ESP8266 WiFi module with the Arduino environment
[06] Techiesms: World’s Smallest IoT Project using the ESP8266 01 module
[07] Becky's IoT Class: communicate with the ESP8266 and Arduino. Note: does not include App Inventor but if you want to know all about the ESP8266, very informative
[08] Andreas Spiess: 📽 Video: Power Saving with ESP8266 (Sleep Mode) Tutorial with some Tricks
[09] Geekstips: Internet Of Things Project – Communication Between ESP8266 Modules Arduino Tutorial
[10] Electronics Hub: Control a Relay using ESP8266 and Android MIT App Inventor

ESP32 WiFi & Bluetooth Mini Microcontroller    Back 

🔥 Hot Tip: The ESP32 can be used with or without a companion microcontroller.

[01] Predictable Designs: ESP32 as a microcontroller via Arduino IDE
[02] Random Nerd: TTGO T-Journal ESP32 Camera
[03] 🔥 Random Nerd Tutorials: Arduino Trouble-shooting Guide
[04] Everything ESP: ESP32 Arduino Tutorial: Alarm with PIR motion sensor and buzzer
[05] Juan Antonio: BLE ESP32 Bluetooth Send Receive Arduino to from App Inventor App
[06] EverythingESP: Raspberry Pi 3 Flask Tutorial: Receiving HTTP POST Request from ESP32 (App Inventor not included but very handy info)
[07] Random Nerd: Getting Started with ESP32 Bluetooth Low Energy (BLE) on Arduino IDE (App Inventor not included but very handy info)
[08] Random Nerd: ESP32-CAM Troubleshooting Guide: Most Common Problems Fixed (App Inventor not included but very handy info)
[09] Junxiao Shi (Your Sunny): ESP32-CAM OV2640 camera Library for Arduino IDE: Define Sketch to send/stream images to App Inventor App)
[10] 🔥 Random Nerd: ESP32 with Bluetooth and Bluetooth Low Energy: The Ultimate Guide (App Inventor not included but essential info)
[11] YouTube: Davy Wybiral: ESP32-Cam Quickstart with Arduino Code using YourSunny's camera Library

LinkIt    Back 

[01] MIT: IoT: Introduction: LinkIt
[02] MIT: IoT: LinkIt 7697
[03] MIT: IoT: LinkIt Smart 7688/7688 Duo (Compatible with Arduino)
[04] CAVEDU: 📽 Video: LinkIt 7697 component for App Inventor
[05] Hackster.io: CAVEDU: App Inventor + IoT: Wi-Fi RGB LED control with LinkIt 7697
[06] Hackster.io: CAVEDU: App Inventor: Bluetooth Low Energy LED control with LinkIt 7697
[07] App Inventor TW: Project: App Inventor + IoT: LED Blink with LinkIt 7697
[08] App Inventor TW: Project: App Inventor + IoT: LED Blink with LinkIt 7697 📽 Video

BBC micro:bit    Back 

🔥 Hot Tip: Pairing: This is when you connect your device (smartphone or tablet) to your micro:bit for the first time.

[01] MIT: App Inventor Extension for micro:bit
[02] MIT: IoT: Introduction: BBC micro:bit
[03] MIT: IoT Starter Tutorial
[04] MIT: micro:bit LED
[05] MIT: micro:bit Temperature Sensor
[06] MIT: micro:bit Potentiometer
[07] Microsoft: micro:bit script editor (Read/Write/Create micro:bit hex files)
[08] Barry Byford: 📽 YouTube: MIT App Inventor BLE to micro:bit
[09] CAVEDU: 📽 YouTube: micro:bit pin control with App Inventor and Bluetooth (BLE)
[10] Lancaster University: Bluetooth (BLE) profile for micro:bit
[11] micro:bit support: Pairing and Flashing code via Bluetooth (BLE)
[12] micro:bit support: What are the different Bluetooth Pairing Modes?
[13] UK Baz: Creating an Android App for your micro:bit with App Inventor and Bluetooth (BLE)
[14] MIT: micro:bit Educational Foundation (MIT microbit home website)
[15] sparkfun: Derek Runberg: Building a weather station with micro:bit and App Inventor
[16] micro:bit guide: Mobile Apps for micro:bit
[17] micro:bit tech: micro:bit Power Supply
[18] micro:bit Support: Why doesn't my computer detect my micro:bit?
[19] micro:bit Support: Fault finding with a micro:bit
[20] Bluetooth.com: Developing Applications for the BBC Microbit
[21] MakeCode: Martin Woolley: Bluetooth SIG: About Bluetooth

Nordic Thingy 52    Back 

[01] Nordic Semiconductor: Nordic Thingy 52 home page
[02] Nordic Semiconductor: Nordic Thingy 52 Software development kit to create custom firmware for Thingy
[03] Android Authority: Gary Sims: 📽 Video: Nordic Thingy 52 Explained
[04] Symmetry Electronics: Cobus Heukelman: 📽 Video: Nordic Thingy 52 Demonstration
[05] Nordic Semiconductor: Pär Håkansson: 📽 Video: Nordic Thingy 52 Introduction
[06] Nordic Semiconductor: Getting started with Nordic Thingy 52 Iot Sensor Kit
[07] Espruino (Web IDE): Nordic Thingy 52 Projects (Note: none are specific to App Inventor but could form the basis for App Inventor IoT use)
[08] Embedded Artistry: Philip Johnston: Nordic Thingy 52 Kit Specifications
[09] Nordic Semiconductor: Google Play: Nordic Thingy 52 App

STM32 32bit microcontroller (ARM Cortex)    Back 

[01] Solderer TV: Communication Between The STM32 And Android Via Bluetooth (HC-06)
[02] CircuitDigest: Interfacing Bluetooth HC-05 with STM32-F103C8 Blue Pill: Controlling LED
[03] STMicroelectronics: 📽 Video: Getting started with Bluetooth Low Energy expansion board (STM32 ODE)
[04] ST Life: PDF: BLUEMICROSYSTEM3 expansion software package for STM32-Cube

PIC micrcontrollers    Back 

[01] DesignSpark: Basics of PIC16F877A microcontroller
[02] components101: PIC16F877A microcontroller features, pin config, programming
[03] components101: PIC16F877A microcontroller data sheet (PDF)
[04] Bas van der Sluis: 📽 How to program PIC microcontrollers 📽 YouTube
[05] Professor Douglas Soares, Brazilian Aeronautics Institute of Technology: Racing robots with App Inventor and PIC microcontroller 📽 YouTube
[06] Electrotec: App Inventor, PIC16F877A microcontroller and Bluetooth HC05 📽 YouTube
[07] Microchip: PIC microcontrollers Forum
[08] EPE Magazine: Hobby Electronics

Raspberry Pi    Back 

[01] Adel Kassah: Get Data from Raspberry Pi with App Inventor 📽 YouTube
[02] Digital Polymath: App Inventor 2 to Control our RPi Robot ** Digital Polymath website is down **
[03] EverythingESP: Raspberry Pi 3 Flask Tutorial: Receiving HTTP POST Request from ESP32 (App Inventor not specifically included)
[04] DF ROBOT: 30 Awesome Projects for a Raspberry Pi (App Inventor not included but some projects can be adapted to use an App)
[05] 🔥 Juan Antonio: Raspberry Pi. Bluetooth. Send. Receive. App Inventor

8051 8-bit microcontroller (Intel MCS-51) [Embedded Systems]    Back 

[01] NPTEL: PDF: Specifications: Intel 8051 microcontroller
[02] EL-PRO-CUS: Introduction to 8051 Programming in Assembly Language (The polar opposite to App Inventor coding but super-interesting)
[03] introbotics: 8051 Microcontroller Programming Tutorials, Simulators, Compilers and Programmer. Huge links library.
[04] NBCAFE: Ports in 8051 microcontroller. A nicely presented description of the Ports, with diagrams.
[05] Electronics Hub: Bluetooth Controlled Electronic Home Appliances with 8051 Microcontroller, HC-05 Bluetooth Module, Android App (which could be defined in AI)
[06] Electronics & Communication Engineering: Umesh Dutta: Robot controlled with App Inventor, Bluetooth HC05 and 8051 Microcontroller

Blue Fruit LE    Back 

The Bluefruit Boards are based on Arduino. They have BLE already built-in for ease of set-up and reliabilty.

It should be noted though that only a few App Inventor Users have used BlueFruit and they have mostly struggled with the communications. MIT Power User Gerrikoio has built an excellent sample project to help. Note: Update the BLE extension if you use Gerrikoio's Project File.

Hackster IO: Gerrikoio: Bluefruit LE: BLE LED Controller: Feather 32u4 + MIT App Inventor Project

Bluetooth    Back 

App Inventor BLE requires your device (e.g. SmartPhone) to have Android v5.0 or higher to avoid known issues with Google's Bluetooth LE support prior to Android 5.0.

Some Smartphones will not work with BLE unless Google Location is activated. Android Marsh Mallow (v6) and up. This is a Google Android security measure

Download the latest MIT BLE Extension: Version: 20240822 Released: 22-08-2024 Package Name: edu.mit.appinventor.ble-20240822.aix

Fixes Critical issues: MIT BLE Extension

🔥 Hot Tip for BLE: Some of the BLE modules arrive with very little information (or none at all). To communicate with them, you need their UUIDs. Bluepixel Technology have written a Scanner App to help verify UUIDs. Down load it from the Google Play Store: BLE Scanner

🔥 Hot Tip for BLE: The data size is limited by the maximum transmission unit (MTU) of the Bluetooth device, which is typically 23 bytes, including the payload (your data, 20 bytes). If the MTU is resized, the BLE spec says that the max payload for v4.2 and v5.0 is 244 bytes. Depending on the device, this could be more, 512 bytes (517 bytes on Android).

🔥 Hot Tip for Bluetooth: Define your code appropriately if your App needs to both send and receive. Think of a Bluetooth signal as water running through a pipe - it can't go in both directions at the same time (Increasing BLE MTU turns that pipe into a tunnel!).

Troubleshoot Bluetooth Issues

There are many reasons why there would be an issue (no specific order):

• One of the devices does not have Bluetooth switched on.
• One of the devices is already connected to a different device.
• One of the devices has an incompatible version of Bluetooth.
• Poor wire connection in the hardware project, including tarnished wire filaments, damaged wire filaments/connectors - things you can't actually see when they are the joint between the wire and the connector.
• Damaged Bluetooth Module. Possible damage to the pins or hairline crack in the body (magnifying glass useful to detect this issue).
• Faulty manufacture of Bluetooth Module.
• The Smartphone's Bluetooth - lower Bluetooth version, weak signal. The manufacturers of the bargain smartphones cut corners on lesser-used items.
• Project design - not allowing enough time for the App to find the device - use a Clock Timer.
• Difference in baud rate between hardware and software (Script/Sketch).
• The Bluetooth Connection requires Location to be switched on (BLE requires Fine Location).
• Using the MIT App Inventor Companion instead of a compiled APK.
• Out of range - the App device is too far away from the hardware device.
• Insufficient or intermittent power supply to the microcontroller (e.g. Arduino). This is a factor missed by many people.
• App device low power (low battery).
• Antenna gain. The integrated antenna of the HM-10 module is insufficient, indicating that the module is not genuine but a third-party clone/copy. A genuine HM-10 is manufactured by JNHuaMao Technology. It's possible to add an external antenna.
• Malware corruption of Bluetooth system files.
• Anti-Virus/Anti-Malware corruption of Bluetooth system files.
• The Maximum Bluetooth Packet Payload Size has been exceeded (20 bytes, or BLE MTU resize 244 bytes)

Enter your Text to Calculate the UTF-8 String Byte Size (size + 1 for end-of-data-mark)
String Byte Size Clear

Sources of Signal Interference:

• Solid obstacles between sender and receiver - walls, doors, furniture, people etc.
• Large mass of metal absorbing the Bluetooth Signal - wall heater/radiator etc.
• Mains (AC) electricity cabling too close.
• Smart home devices such as hubs, plugs, light bulbs, smart speakers/pods (e.g. Echo, Nest, Alexa) use different radio systems such as Zigbee which can interfere with Bluetooth signals (same Ghz spectrum).
• Domestic devices/machines such as microwave ovens or anything with a 'smart' feature/internet connection.
• The DC cables of the microcontroller (e.g. Arduino) too close to the circuit cables and/or BT module.
• PC being used as a Serial Monitor.
• The cable between the PC and the microcontroller (e.g. Arduino).
• PC's UPS module/device.
• PC's Bluetooth broadcast.
• PC's and/or router's WiFi signal.
• USB Bluetooth dongle for a wireless mouse, keyboard, or other accessory.
• Domestic cooling fans generate an electromagnetic field that can interfere with signals.
• Fluorescent strip lights have an electromagnetic field.
• The housing for the microcontroller is made of/contains elements of metal (screws, hinges etc).

Bluetooth Range (maximum distance between Sender and Receiver) is an ever-present challenge, especially indoors. Ensure there are as few physical barriers as possible (walls, doors, furniture, people).

The Bluetooth Range Estimator

Your Own BLE UUIDs

BLE uses UUIDs (universally unique identifiers for Services and Characteristics). You can define your own UUIDs right here!

Note: Do not use many Characteristic UUIDs when it is not necessary. For example, if sending three integer values to your App, they can share the same UUID.

Make UUIDs Clear Validate UUID (from any source)

Note: If your Browser denies Copy to Clipboard, use Ctrl+A select, Ctrl+C copy, Ctrl+V paste

Note: The Clear buttons also clear the Clipboard (Compatible Browsers: FireFox, Chrome, Brave, Avast Secure, AVG Secure, Edge)

Service UUID:
To Clipboard

Characteristic UUID 1:
To Clipboard

Characteristic UUID 2:
To Clipboard

Characteristic UUID 3:
To Clipboard

Characteristic UUID 4:
To Clipboard

Characteristic UUID 5:
To Clipboard

Characteristic UUID 6:
To Clipboard

Validate UUID: Custom (36 character) UUIDs only
Validate Clear

Links

[01] Jon Gunnar Sponås: Effective Range of Bluetooth Communications
[02] MIT: BluetoothLE (BLE) App Inventor Blocks
[03] MIT:Bluetooth Client, Bluetooth Server
[04] xkcd: Bluetooth Blues :)
[05] Bluetooth.com: BLE Assigned Numbers e.g. GATT Characteristics
[06] Instructables: Arduino Bluetooth HC06 (any microcontroller)
[07] Instructables: Arduino Bluetooth HC05
[08] Robo India: Sending-Receiving with HC05 and App Inventor (any microcontroller)
[09] Martyn Currey: Arduino, HM-10 BLE Module and App Inventor 2
[10] Martyn Currey: HM-10 Bluetooth 4 BLE Modules
[11] PDF: Basic Two Way Bluetooth Communication via HC-05 Or HC-06 Between Arduino and Android (Not specific to App Inventor. Very informative nonetheless)
[12] Juan Antonio: 🔥 BLE ESP32 Bluetooth Send Receive Arduino App Inventor App
[13] Mohammad Afaneh: NovelBits: How to achieve maximum throughput for your BLE application
[14] Mohammad Afaneh: NovelBits: eBook: Intro to Bluetooth Low Energy
[15] Juan Antonio: 🔥 Bluetooth HC-06 Send and Receive Arduino to-from App Inventor App. Send Text File. Send Image.
[16] Random Nerd: Getting Started with ESP32 Bluetooth Low Energy (BLE) on Arduino IDE (App Inventor not included but very handy info)
[17] Random Nerd: Rui Santos: 📽 Getting Started with ESP32 Bluetooth Low Energy (BLE) on Arduino IDE (Video)
[18] PunchThrough: Chee Yi Ong: 🔥 Ultimate Guide: Android Bluetooth Low Energy (BLE)

BR:	Basic Data Rate max 1Mbps
EDR:	Enhanced Data Rate max 3MBps
HS:	High Speed Data Rate max 24Mbps
SAM:	Slot Availability Masking - detect and prevent interference on neighbouring radio bands
A2DP:	Advanced Audio Distribution Profile - Optional Bluetooth Stereo profile which defines how high quality stereo audio can be streamed from one device to another
AptX:	Compression Enhancement of A2DP - requires supporting codec in both devices
AptX HD:	Compression Enhancement of A2DP - requires supporting codec in both devices
Classic:	Higher power consumption, less advanced comms. *version 3.x consumes more power than v2.x
BLE:	Bluetooth Low Energy (for battery powered devices), advanced comms with GATT Generic Attributes hierarchical data structure

Wireless Technologies    Back 

Including Bluetooth, there are many other wireless technologies to choose from!

John Teel: Comparison of Wireless Technologies Bluetooth Classic, WiFi, BLE, Zigbee, Z-Wave, 6LoWPAN, NFC, WiFi Direct, GSM, LTE, LoRa, NB-IoT, and LTE-M

Robots

LEGO MINDSTORMS    Back 

MIT: IoT: Introduction: LEGO® MINDSTORMS® EV3 robot platform
MIT: LEGO® MINDSTORMS® NXT robots using Bluetooth

MIT App Inventor Codi Bot    Back 

MIT: IoT: Introduction: Codi Bot
Maker Fair Hong Kong: 📽 Video: App Inventor Bee Bot

Video Formats

MIT: App Inventor: Android Video Player Formats Supported

App Inventor Extensions

• Before you start looking for an extension, ask yourself if you really need one - can you achieve your aim with the native App Inventor Blocks?
• To enable an extension after loading it into App Inventor, drag and drop it on to the Designer Work Space (device image)
• Note: when installing an Extension, the Companion App must not be connected to App Inventor!
• The Emulator is intended for quick, small code tests. It won't be able to cope with most extensions - best to use the Companion on your device

Extensions Library maintained by App Inventor Expert Taifun Baer, including his own excellent Products:

Pura Vida: App Extensions

Extensions Library maintained by App Inventor Power Users (including Taifun) and MIT:

MIT App Inventor Forum: App Extensions