Mit App Inventor And Arduino | Projects With Mit App Inventor

Step 1: The Bluetooth Module

The most common bluetooth module today is the HC-06 or HC-05. It costs about 7-10 dollars online. Look at the image below to see how to hook it to the Arduino.

That is pretty easy right? Just four jumper wires and you now have wireless serial connectivity to your arduino. Now, if you have a program where you have been sending commands to the arduino with the Serial Monitor you can now do that wirelessly with a bluetooth device. (Note: You can upload programs to the arduino via bluetooth, but that is significantly more complicated than what we want to achieve here.)

Experiments

4.Experimental Setup

We crawled 524 high-quality Scratch projects on the Scratch website. More specifically, we crawled (1) 24 “starter projects” as shown on the Ideas menu, which consists of tutorial projects categorized as animations, games, interactive art, music and dance, stories and video sensing; and (2) 500 “popular” and “trending” projects on the Explore menu, which consist of the animations, art, games, music and story projects.

We also crawled 379 mature projects on the App Inventor website, consisting of (1) official tutorials, (2) all of the popular projects “liked” by greater than or equal to ten users, and (3) all of the App of the Month (AOM) projects from January of 2015 to August of 2019. Note that only 209 projects received greater than or equal to ten “likes,” and that 67 AOM projects are developed by adults while the other 89 AOM projects are invented by primary or secondary school students. We excluded projects that could only be downloaded from the Google Play Store because we cannot access to their source codes. We also excluded projects with broken hyperlinks.

4.Experimental Results on Computational Thinking Concepts: ScratchApp Inventor

App Inventor projects scored higher in the areas of User Interactivity and Data Representation. The high User Interactivity score may stem from the fact that we often need to use the event blocks of a component when we need to exploit the functionalities of the component. Additionally, the high score for Data Representation may be due to the fact that there are many command blocks that require a list as input.

In summary, the effectiveness scores for Scratch and App Inventor projects showed significant differences. More specifically, Scratch projects outperformed App Inventor projects in the areas of Parallelism, Synchronization and Flow Control. On the other hand, App Inventor projects outperformed Scratch in the areas of User Interactivity and Data Representation.

4.Detailed Analysis of the Results

It is interesting to note that projects with high overall scores show significant score improvements in the “weak areas” of each programming language. For example, while the Data Representation score for the Scratch starter projects is 1.08, that for the popular game projects is 2.34. Similarly, while the Parallelism score of the App Inventor tutorials is 0.50, that for the App of the Month (adult) projects is 1.67. These results indicate that even if we learn only one programming language, we can develop comprehensive computational thinking skills if we can make good use of that language.

In summary, even if students learn only one programming language, they can develop comprehensive computational thinking skills by making good use of that language. However, each programming language is superior to the other in certain computational thinking areas. Thus, it could be more helpful for students to learn both Scratch and App Inventor to gain a broader sense of computational thinking concepts.

4.Threats of Validity

Although we believe that our findings can be helpful for many computer science educators and K-12 teachers, this paper has the following limitations.

Related Work

Step 3: App Inventor

The basics of app inventor are easy. If you know how to code you can struggle through the basic set-up and operation. So just fiddle around until you have a button or slider bar that you want to use then you can add in this bluetooth code. In the context of the tutorial the app is that of the LittleArm Arduino Robot Arm, which has multiple sliders. But we will focus on just one.

Overview

For this tutorial we have two examples. The first example is controlling a simple LED and the second one is controlling a Stepper Motor using smartphone. In my previous tutorial we already learned how to make the Bluetooth communication between the Arduino Board and the Smartphone using the HC-05 Bluetooth module and explained the Arduino code needed for the first example.

Introduction: Using MIT App Inventor to Control Arduino – the Basics

We all have a smartphone. Now, with that statement of the obvious, let me ask you this. Why is your Arduino hardly ever connected to your smartphone. Bluetooth costs about $8 to implement on an arduino. The main issue is that some people get hung-up on the issue of programming bluetooth, so they just keep the usb cord. So here is the absolutely most basic things you need to use bluetooth with android and arduino.

This tutorial will go through the bare minimum you need to create an connection between a custom android app you make with MIT App Inventor and the Arduino.

All code and references provided are based on the code from the LittleArm Arduino robot arm.

Step 5: App Inventor: Create a ListPicker

Create a listpicker so that you can use to find and select the bluetooth devices that are paired with the smartphone.

When the listpicker is open, then a selection should trigger some event. In this case, a Bluetooth connection to the device listed. (Ignore the last three green blocks those are specific “trees” in the forest that you don’t have to have.)

Step 8: Enjoy Your App

And that is all there is to it. You now have an app, that will connect with a bluetooth device and then send some kind of data to the Arduino and receive some kind of data via serial communications. Now you can control almost any arduino project with your android smartphone. Enjoy.

You can see a demo of the app that all of this code was taken from in this video.

Hello friends,

In this topic I am going to show some examples of Arduino UNO with the Bluetooth HC-06 module.

I will start with simple examples and later I will put some more complicated codes.

Hello friends,

In this topic I am going to show some examples of Arduino UNO with the Bluetooth HC-06 module.

I will start with simple examples and later I will put some more complicated codes.

1.- App sends simple char. Arduino on-off LED12 and LED13.

p9A0i_bluetooth_caracter.aia (2.4 KB)


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm #define Pin12 12 #define Pin13 13 char caracter; void setup() { Serial.begin(9600); pinMode(Pin12, OUTPUT); pinMode(Pin13, OUTPUT); } void loop() { if(Serial.available()) { caracter = Serial.read(); if(caracter == 'a'){ digitalWrite(Pin12, HIGH);} if(caracter == 'b'){ digitalWrite(Pin12, LOW);} if(caracter == 'c'){ digitalWrite(Pin13, HIGH);} if(caracter == 'd'){ digitalWrite(Pin13, LOW);} } }


Instead of using LEDs you can put Relays.

2A.- App sends text. Arduino on-off LED12 and LED13. Serial Monitor. With asterisk.

p9A0i_bluetooth_texto.aia (2.6 KB)


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm #define Pin12 12 #define Pin13 13 char caracter; String palabra; void setup() { Serial.begin(9600); pinMode(Pin12, OUTPUT); pinMode(Pin13, OUTPUT); } void loop() { if(Serial.available()) { caracter = Serial.read(); palabra = palabra + caracter; if(caracter == '*') { palabra = palabra.substring(0, palabra.length() - 1); // Delete last char * Serial.println(palabra); if (palabra == "on12"){digitalWrite(Pin12, HIGH);} if (palabra == "off12"){digitalWrite(Pin12, LOW);} if (palabra == "on13"){digitalWrite(Pin13, HIGH);} if (palabra == "off13"){digitalWrite(Pin13, LOW);} palabra = ""; delay(100); } } }


oooooooooooooooo0000000000000000ooooooooooooooooooo

2B.- App sends text. Arduino on-off LED12 and LED13. Serial Monitor. Without asterisk.

p9A0i_bluetooth_texto_2.aia (2.6 KB)


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm #define Pin12 12 #define Pin13 13 char caracter; String palabra; void setup() { Serial.begin(9600); pinMode(Pin12, OUTPUT); pinMode(Pin13, OUTPUT); } void loop() { if(Serial.available()) { caracter = Serial.read(); palabra = palabra + caracter; Serial.println(palabra); if (palabra.indexOf("on12")>= 0){digitalWrite(Pin12, HIGH); palabra = "";} if (palabra.indexOf("off12")>= 0){digitalWrite(Pin12, LOW); palabra = "";} if (palabra.indexOf("on13")>= 0){digitalWrite(Pin13, HIGH); palabra = "";} if (palabra.indexOf("off13")>= 0){digitalWrite(Pin13, LOW); palabra = "";} delay(100); } }


3.- App sends several information at the same time.

In this example we will use the same App as in the previous example.

Suppose we want to send two information at the same time, for example we want to turn on LED12 and turn off LED13.

We write in the TextBox: on12, off13 [the asterisk will be added automatically at the end of this text]

The Arduino code will check if the text sent contains the string: on12, off12, on13, off13

To check if a substring is in a text we use indexOf: if(palabra.indexOf(“on12”)>= 0)

We can also put the text in another order: off13, on12


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm #define Pin12 12 #define Pin13 13 char caracter; String palabra; void setup() { Serial.begin(9600); pinMode(Pin12, OUTPUT); pinMode(Pin13, OUTPUT); } void loop() { if(Serial.available()) { caracter = Serial.read(); palabra = palabra + caracter; if(caracter == '*') { palabra = palabra.substring(0, palabra.length() - 1); // Delete last char * Serial.println(palabra); if(palabra.indexOf("on12")>= 0){digitalWrite(Pin12, HIGH);} if(palabra.indexOf("off12")>= 0){digitalWrite(Pin12, LOW);} if(palabra.indexOf("on13")>= 0){digitalWrite(Pin13, HIGH);} if(palabra.indexOf("off13")>= 0){digitalWrite(Pin13, LOW);} palabra = ""; delay(100); } } }


4.- App sends three values separated by comma. Arduino receives them and separates them.

In this example we will use the same App as in the previous example.

We assume that the App wants to send these numbers separated by commas to the Arduino: 126,3,58

An asterisk will be added indicating end of message. [126,3,58*]

In this case it is necessary to indicate the end of the message (example with asterisk) since we can send any number.

Arduino will receive that text and separate it by the comma.

Check Serial Monitor.


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm char caracter; String palabra; String red; String green; String blue; int ind1; int ind2; int ind3; void setup() { Serial.begin(9600); } void loop() { if(Serial.available()) { caracter = Serial.read(); palabra = palabra + caracter; if(caracter == '*') { palabra = palabra.substring(0, palabra.length() - 1); // Delete last char * Serial.println(palabra); ind1 = palabra.indexOf(','); red = palabra.substring(0, ind1); ind2 = palabra.indexOf(',', ind1+1 ); green = palabra.substring(ind1+1, ind2); ind3 = palabra.indexOf(',', ind2+1 ); blue = palabra.substring(ind2+1); Serial.print("red = "); Serial.println(red); Serial.print("green = "); Serial.println(green); Serial.print("blue = "); Serial.println(blue); Serial.println(); palabra = ""; delay(10); } } }


ooooooooooooooo000000o000000oooooooooooooooAnother way to split the data in with this getValue function:


Serial.println(palabra); red = getValue(palabra,',',0); green = getValue(palabra,',',1); blue = getValue(palabra,',',2); (...) ///////////////// Function Split by char //////////////// String getValue(String data, char separator, int index) { int found = 0; int strIndex[] = {0, -1}; int maxIndex = data.length()-1; for(int i=0; i<=maxIndex && found<=index; i++){ if(data.charAt(i)==separator || i==maxIndex){ found++; strIndex[0] = strIndex[1]+1; strIndex[1] = (i == maxIndex) ? i+1 : i; } } return found>index ? data.substring(strIndex[0], strIndex[1]) : ""; }


5.- App requests temperature and humidity to the Arduino. The Arduino sends values.

p9A0i_bluetooth_temperatura.aia (3.3 KB)

When Click in tempe_humidity Button, App sends the character “D”.Arduino concatenates the temperature and humidity Strings separated by a comma:37,80

App ReceiveText 37,80 converts it to a list and separates the values.

Note: the DelimiterByte must have the value 10. [10 is ASCII New Line, LF. Arduino \n]

In this Arduino code I do not use the sensor or the I2C LCD to simplify its content.Here you can see the code with the sensor and the I2C LCD


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm char caracter; int temperature = 0; int humidity = 0; String tempera_humidity; void setup() { Serial.begin(9600); } void loop() { temperature = random(20,40); humidity = random(50,95); delay(500); if(Serial.available()) { caracter = Serial.read(); if(caracter == 'T'){Serial.println(temperature);} if(caracter == 'H'){Serial.println(humidity);} if(caracter == 'D'){ tempera_humidity = (String) temperature + "," + (String) humidity; Serial.println(tempera_humidity); } } }


6.- App checks status 2 PushButtons.

p9A0i_bluetooth_pulsadores.aia (3.4 KB)


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm char caracter; #define push7 7 // PushButton 7. #define push8 8 // PushButton 8. String status_push7; String status_push8; String status; void setup() { Serial.begin(9600); pinMode(push7, INPUT); pinMode(push8, INPUT); } void loop() { delay(50); if(Serial.available()) { caracter = Serial.read(); if (digitalRead(push7) == HIGH) {status_push7 = "Push7 ON";} else {status_push7 = "Push7 OFF";} if (digitalRead(push8) == HIGH) {status_push8 = "Push8 ON";} else {status_push8 = "Push8 OFF";} status = status_push7 + "," + status_push8; if(caracter == '7'){Serial.println(status_push7);} if(caracter == '8'){Serial.println(status_push8);} if(caracter == 'D'){Serial.println(status);} } }


7.- App gets the value of two potentiometers.

p9A0i_bluetooth_potenciometro.aia (3.3 KB)


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm int value_pot0; int value_pot1; String value; void setup() { Serial.begin(9600); } void loop() { value_pot0 = analogRead(A0); value_pot1 = analogRead(A1); value = (String) value_pot0 + "," + (String) value_pot1; Serial.println(value); delay(200); // It should be slower than the Clock Interval. }


8.- App receives data from Arduino. Clock.Interval. Arduino delay. Buffer.

p9A0i_bluetooth_aleatorio.aia (2.9 KB)

a)Clock.Interval = 300Arduino delay = 200

App cannot process the information because the Clock “is slower” than the Arduino.The buffer is being filled, values that arrive and have not yet been processed.

When the Buffer reaches a certain value, for example 120, you remove power to the Arduino. What happens with buffer?

b) Change Clock.IntervalClock.Interval = 100Arduino delay = 200

Therefore, Clock.Interval < delay Arduino


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm int aleatorio; void setup() { Serial.begin(9600); } void loop() { aleatorio = random(0,100); Serial.println(aleatorio); delay(200); // Clock.Interval < delay Arduino }


9.- A potentiometer in Arduino sends values to the App. Dynamic graph. Shift left.

p9A0i_bluetooth_dinamico.aia (8.1 KB)


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm int value_pot0; void setup() { Serial.begin(9600); } void loop() { value_pot0 = analogRead(A0); Serial.println(value_pot0); delay(100); // It should be slower than the Clock Interval. }


10.- Three LEDS on-off according to a sequence saved in a file.

p9A0i_bluetooth_secuencia3LED.aia (5.0 KB)

In file rutina2.csv this content:

Levels of: LED11 – LED12 – LED13 – Time in seconds of this combination.

App sends 1-1-0-2*

Arduino set LEDs on, on, off

and wait 2 seconds.

then Arduino sends to App “send_me_next”

When App receives “send_me_next”

App “send_next” combination: 1-0-0-2*


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm char caracter; String palabra; int LED11 = 11; int LED12 = 12; int LED13 = 13; int valor11; int valor12; int valor13; int Tiempo = 1000000; unsigned long currentMillis; unsigned long previousMillis = currentMillis; int k1; int k2; int k3; int k4; void setup() { Serial.begin(9600); pinMode(LED11, OUTPUT); pinMode(LED12, OUTPUT); pinMode(LED13, OUTPUT); } void loop() { if(Serial.available()) { caracter = Serial.read(); palabra = palabra + caracter; Serial.println(palabra); if(caracter == '*') { palabra = palabra.substring(0, palabra.length() - 1); // Delete last char * k1 = palabra.indexOf('-'); valor11 = palabra.substring(0, k1).toInt(); k2 = palabra.indexOf('-', k1+1); valor12 = palabra.substring(k1+1, k2).toInt(); k3 = palabra.indexOf('-', k2+1); valor13 = palabra.substring(k2+1, k3).toInt(); k4 = palabra.indexOf('-', k3+1); Tiempo = 1000 * palabra.substring(k3+1, k4).toInt(); palabra = ""; digitalWrite(LED11, valor11); digitalWrite(LED12, valor12); digitalWrite(LED13, valor13); } previousMillis = currentMillis; } // =>Fin del available tiempo(); } // =>Fin del loop void tiempo() { currentMillis = millis(); if (currentMillis >= (previousMillis + Tiempo)) { previousMillis = currentMillis; Serial.println("send_me_next"); // Envíame el siguiente. } }


11.- Virtual Screen with two VerticalArrangement.

p9A0i_bluetooth_virtual.aia (4.1 KB)


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm #define LED13 13 byte StatusLED13; void setup() { Serial.begin(9600); pinMode(LED13, OUTPUT); } void loop() { if(Serial.available()) { int dato = Serial.read(); if(dato == 153){digitalWrite(LED13, HIGH);} if(dato == 168){digitalWrite(LED13, LOW);} if(dato == 221){ StatusLED13 = digitalRead(LED13); Serial.print(StatusLED13); // Sends 48 or 49 } } }


12.- App moves two Servos by Sliders.

p9A0i_bluetooth_servos.aia (3.2 KB)


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm #include

Servo servo3; Servo servo5; const int pwmPin3 = 3; // Servo3 pin3 PWM const int pwmPin5 = 5; // Servo5 pin5 PWM char caracter; String palabra; String angulo_1; String angulo_2; int k1; void setup() { Serial.begin(9600); pinMode (pwmPin3, OUTPUT); pinMode (pwmPin5, OUTPUT); servo3.attach(pwmPin3); servo5.attach(pwmPin5); } void loop() { if(Serial.available()) { caracter = Serial.read(); palabra = palabra + caracter; if (caracter == '*') { Serial.println(palabra); palabra = palabra.substring(0, palabra.length() - 1); // Delete last char * k1 = palabra.indexOf(','); angulo_1 = palabra.substring(0, k1); angulo_2 = palabra.substring(k1+1, -1); servo3.write(angulo_1.toInt()); servo5.write(angulo_2.toInt()); palabra = ""; } } } // => Fin Loop



Note: if you use more than 2 servos you will need to power them with an external power source. Video: Each servo needs about 400 mA.

13.- App moves a Stepper motor.

p9A0i_bluetooth_pasopaso.aia (3.1 KB)

In a servo you order:set 34ºset 12ºset 96º, it is not necessary to know the previous position.

In a stepper motor, you order:set 20 step clockwiseset 80 step anticlockwise, it is necessary to know the previous position to place it in a new position.

I will use: Stepper motor 28BYJ-48 ULN2003

It is convenient to power this motor through an external source, in this experimental example I will feed it with the 5 V of Arduino.


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm #include

#define STEPS 64 // Secuencia 1-3-2-4 Stepper motor(STEPS, 8, 10, 9, 11); char caracter; void setup() { Serial.begin(9600); motor.setSpeed(200); } void loop() { if( Serial.available() ) { caracter = Serial.read(); Serial.print(caracter); if(caracter == '1'){motor.step(60);} if(caracter == '2'){motor.step(-60);} if(caracter == '3'){motor.step(510);} if(caracter == '4'){motor.step(-510);} if(caracter == '5'){motor.step(1020);} if(caracter == '6'){motor.step(-1020);} if(caracter == '7'){motor.step(2040);} if(caracter == '8'){motor.step(-2040);} if(caracter == 'A'){motor.step(100);} if(caracter == 'B'){motor.step(-100);} } }



14. Where do we connect the Bluetooth module in Arduino UNO?

p9A0i_bluetooth_Serial.aia (2.9 KB)

Terminals 0 (RX) and 1 (TX) are used by Arduino as the default Serial RX/TX. Use it to upload sketch, Serial Monitor, Bluetooth. So when we are going to upload a sketch for Bluetooth we must disconnect the RX cable from the Arduino.

We can use other terminals to connect the Bluetooth module, for example 10 and 11, in this case we need the “SoftwareSerial” library. Now when we upload a sketch it is not necessary to remove the RX cable.

– CODE FOR MODULE IN default RX/TX pin 0 and 1 of Arduino.


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm #define Pin13 13 char caracter; void setup() { Serial.begin(9600); pinMode(Pin13, OUTPUT); } void loop() { if(Serial.available()) { caracter = Serial.read(); if(caracter == 'a'){ digitalWrite(Pin13, HIGH);} if(caracter == 'b'){ digitalWrite(Pin13, LOW);} Serial.println(caracter); } }


– CODE FOR MODULE IN pin10 and pin11 with SoftwareSerial library.


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm #include

SoftwareSerial I2CBT(10,11); // El TX del módulo BT va al pin10 del Arduino // El RX del módulo BT va al pin11 del Arduino #define Pin13 13 char caracter; void setup() { I2CBT.begin(9600); // To read and write Bluetooth Serial.begin(9600); // To print in Serial Monitor pinMode(Pin13, OUTPUT); } void loop() { if(I2CBT.available()) { caracter = I2CBT.read(); if(caracter == 'a'){ digitalWrite(Pin13, HIGH);} if(caracter == 'b'){ digitalWrite(Pin13, LOW);} Serial.println(caracter); // Serial Monitor I2CBT.println(caracter); // return Bluetooth // I2CBT.write(caracter); // return Bluetooth } }



15.- Send text file from Server to Client and from Client to Server. Message Mobile to Mobile by Bluetooth.

p9A0i_BT_Server_File.aia (3.3 KB)

p9A0i_BT_Client_File.aia (3.4 KB)

– Blocks Server.

– Blocks Client.

16.- Send Image file from Server to Client and from Client to Server.

This example is only experimental, there are problems with file size, clock interval, conversion … Try.

p9A0i_BT_Server_Image.aia (41.9 KB)

p9A0i_BT_Client_Image.aia (55.6 KB)

– Blocks Server.

– Blocks Client.

17.- Write number with KeyPad in Arduino and sends to App by Bluetooth. LCD I2C.

p9A0i_bluetooth_teclado.aia (1.8 MB)


// Juan A. Villalpando // http://kio4.com/appinventor/9BA_bluetooth_teclado_LCD.htm #include

#include

// Pantalla LCD #include LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); // LiquidCrystal_I2C lcd(0x3F, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); String clave = ""; String clave_old = ""; const byte ROWS = 4; const byte COLS = 4; char keys[ROWS][COLS] = { {'1', '2', '3', 'A'}, {'4', '5', '6', 'B'}, {'7', '8', '9', 'C'}, {'*', '0', '#', 'D'} }; byte rowPins[ROWS] = {0, 1, 2, 3}; byte colPins[COLS] = {4, 5, 6, 7}; int i2caddress = 0x20; // Module I2C Keyboard. Keypad_I2C kpd = Keypad_I2C( makeKeymap(keys), rowPins, colPins, ROWS, COLS, i2caddress); void setup() { Serial.begin(9600); kpd.begin(); lcd.begin(16,2);// Columnas y filas de LCD. } void loop() { char key = kpd.getKey(); clave = clave + (String) key; if (key == '#') { clave = clave.substring(0, clave.length() - 1); // Delete last char # lcd.clear(); lcd.setCursor(0,0); lcd.print(clave); lcd.setCursor(0,1); lcd.print(clave_old); clave_old = clave; Serial.println(clave); clave = ""; } delay(100); }



18.- Poor man’s circuit.


// Juan A. Villalpando // http://kio4.com/appinventor/9BA_bluetooth_teclado_LCD.htm char key = 0; String clave = ""; void setup() { Serial.begin(9600); } void loop() { if (Serial.available() > 0) { key = Serial.read(); clave = clave + key; if (key == '#') { Serial.print(clave); // Example sends: 123# clave = ""; } } }


19.- Arduino Interrupts sends data to App.

p9A01_bluetooth_interrupt.aia (2.3 KB)

Arduino UNO has two pins for interruptions (pin2 and pin3). ESP32 has 32 interrupt pins).

Arduino interrupts: https://www.arduino.cc/reference/en/language/functions/external-interrupts/attachinterrupt/

When pin2 RISING causes an interrupt and calls function on_13

When pin3 RISING causes an interrupt and calls function off_13


// Juan A. Villalpando // http://kio4.com/appinventor/9A0_Resumen_Bluetooth.htm #define LED13 13 void setup() { Serial.begin(9600); attachInterrupt(digitalPinToInterrupt(2), on_13, RISING); attachInterrupt(digitalPinToInterrupt(3), off_13, RISING); pinMode(LED13, OUTPUT); } void loop() { // } // Interruptions ISR. void on_13() // When pin2 RISING... { digitalWrite(LED13, HIGH); Serial.print(1); } void off_13() // When pin3 RISING... { digitalWrite(LED13, LOW); Serial.print(0); }


In this Arduino Tutorial we will learn how to build custom Android applications for controlling Arduino using the MIT App Inventor online application. You can watch the following video or read the written tutorial below.

Step 6: Send Data to Arduino

Assuming that the connection is successful the light on the HC-06 bluetooth module will become solid. That is good, your device can now talk to the arduino. So to send something to the arduino, just select the type of data you want to send. Is it numbers, letters, bits, bytes, etc. Then select the .SendXXXX operation from the bluetooth menu in AppInventor and stick your data in. In this case for the LittleArm we use .SendText because we have text characters, in this case commas, in the data. If it was numerical we would use SendNumbers and so on.

You may notice that the function that the send command is inside of, is linked to one of the slider bars in the app. This means that the the Send is linked to an “event.” i.e. when the slider is moved it automatically calls this function. Not to bad, right?

Arduino Code

Here’s a quick overview of that code. So, via the serial port we receive the incoming data from the smartphone and store it in the ‘state’ variable. If we receive the character ‘0’ which is sent from the smartphone when the ‘LED: OFF’ button is pressed, we will turn the LED off and send back to the smartphone the String “LED: OFF”. On the other hand, if we receive the character ‘1’ we will turn the LED on and send back the String “LED: ON”.


/* Arduino and HC-05 Bluetooth Module Tutorial * * by Dejan Nedelkovski, www.HowToMechatronics.com * */ int state = 0; void setup() { pinMode(ledPin, OUTPUT); digitalWrite(ledPin, LOW); Serial.begin(38400); // Default communication rate of the Bluetooth module } void loop() { if(Serial.available() > 0){ // Checks whether data is comming from the serial port state = Serial.read(); // Reads the data from the serial port } if (state == '0') { digitalWrite(ledPin, LOW); // Turn LED OFF Serial.println("LED: OFF"); // Send back, to the phone, the String "LED: ON" state = 0; } else if (state == '1') { digitalWrite(ledPin, HIGH); Serial.println("LED: ON");; state = 0; } }

Code language: Arduino (arduino)

So now we need to build our custom Android application which will send those characters ‘0’ and ‘1’ when a particular button is pressed, as well as, receive the incoming Strings from the Arduino.

Step 2: Arduino Code

Some people think that that when you replace the cord with bluetooth that you have to change your code. THEY ARE WRONG. Relax, if your code works with the USB cord than you do not have to change a thing. As I said, bluetooth is basically the same thing as USB in code syntax. The Arduino’s Serial.read is just fine with the same code.

Here is the code that is used with the LittleArm Arduino robot Arm.

//////Other Intiations here

void setup(){ Serial.begin(9600); baseServo.attach(5); // attaches the servo on pin 5 to the servo object shoulderServo.attach(4); elbowServo.attach(3); gripperServo.attach(2); Serial.setTimeout(50); //ensures the the arduino does not read serial for too long Serial.println(“started”); baseServo.write(90); //intial positions of servos shoulderServo.write(100); elbowServo.write(110); ready = 0; }//primary arduino loopvoid loop() { if (Serial.available()){ ready = 1; desiredAngle.base = Serial.parseInt(); desiredAngle.shoulder = Serial.parseInt(); desiredAngle.elbow = Serial.parseInt(); desiredGrip = Serial.parseInt(); desiredDelay = Serial.parseInt();

if(Serial.read() == ‘\n’){ // if the last byte is ‘d’ then stop reading and execute command ‘d’ stands for ‘done’ Serial.flush(); //clear all other commands piled in the buffer Serial.print(‘d’); //send completion of the command } }

This snippet of code is the read and return code. Notice that it reads information from the Serial port just as if there were a usb cable connected. There is no need to initiate ports for the Bluetooth, they are naturally activated.

Stepper Motor Control Example

Now let’s take a look at the second example, controlling a stepper motor. At the top of the screen we have the same components for the Bluetooth connection as the previous example. Next we have a Canvas component which is used for drawing and inserting images. I inserted two transparent images which I previously drew. The first one is an image of a gauge which will be fixed in place and the second one is an image of a pointer which will be rotating. Next we have a Check button for switching between Manual and Auto or continuously running mode and a button for changing the rotation direction. At the button we have a slider for changing the rotation speed of the stepper motor.

Here are the blocks and the Arduino code behind this example. So, in the Blocks editor again we have the same blocks for the Bluetooth connection as the previous example.

Now for rotating the pointer image we use the ImageSprite function “.PointInDirection” which rotates the image from 0° position to the X and Y coordinates where the Canvas has been touched. At the same time we set the rotated ImageSprite heading to the text label above. After that we call custom made procedure, or function which is actually a 10m seconds delay.

Lastly we send the heading value as a Text to the Arduino using the “SendText” Bluetooth function. This value will be accepted by the Arduino and it will rotate the stepper motor accordingly.

Next is the the CheckBox block. So if the CheckBox is checked we will send the text “Auto” to the Arduino which will activate stepper motor to rotate continuously. While we are in this mode if we press the “Reverse” button, we will send the text “Reverse” to the Arduino which will change the rotation direction of the motor. Also, while we are in this mode, we can change the speed of rotation. If we change the position of the slider, the current value of the slider position will be send to the Arduino which will change the rotation speed of the stepper. If we uncheck the CheckBox we will get back into the manual mode. Here’s the demonstration of the example.

Here’s a download file of the above MIT App Inventor project, as well as the two images used in the project:

Here’s the Arduino code of the second example:


/* Stepper Motor Control via HC-05 Bluetooth Module * * by Dejan Nedelkovski, www.HowToMechatronics.com * */ // Defining variables const int stepPin = 7; const int dirPin = 6; String state = ""; int currentHeading=0; int currentAngle=0; int lastAngle=0; int angle=0; int rotate=0; int runContinuously=0; String mode = "Manual"; boolean dirRotation = HIGH; int rotSpeed = 1500; void setup() { // Sets the two pins as Outputs pinMode(stepPin,OUTPUT); pinMode(dirPin,OUTPUT); Serial.begin(38400); // Default communication rate of the Bluetooth module } void loop() { delayMicroseconds(1); if(Serial.available() > 0){ // Checks whether data is comming from the serial port state = Serial.readString(); // Reads the data from the serial port } // When Auto Button is pressed if (mode == "Auto") { if (state == "Reverse") { delay(10); if (dirRotation == HIGH) { dirRotation = LOW; } else { dirRotation = HIGH; } digitalWrite(dirPin,dirRotation); delay(10); state = ""; } rotSpeed = state.toInt(); if (rotSpeed >= 300 && rotSpeed <= 3000) { digitalWrite(stepPin,HIGH); delayMicroseconds(rotSpeed); digitalWrite(stepPin,LOW); delayMicroseconds(rotSpeed); } else { digitalWrite(stepPin,HIGH); delayMicroseconds(1500); digitalWrite(stepPin,LOW); delayMicroseconds(1500); } if (state == "Manual"){ mode = state; } } // When Program is in Manual mode else if (mode == "Manual"){ currentHeading = state.toInt(); //Serial.println(angle); //Serial.println(state); if (currentHeading < 0 ){ currentHeading = 360+currentHeading; } currentAngle = map(currentHeading,0,359,0,200); digitalWrite(dirPin,HIGH); // Enables the motor to move in a particular direction // Makes 200 pulses for making one full cycle rotation if (currentAngle != lastAngle){ if(currentAngle > lastAngle){ rotate = currentAngle - lastAngle; for(int x = 0; x < rotate; x++) { digitalWrite(stepPin,HIGH); delayMicroseconds(500); digitalWrite(stepPin,LOW); delayMicroseconds(500); } } if(currentAngle < lastAngle){ rotate = lastAngle - currentAngle; digitalWrite(dirPin,LOW); //Changes the rotations direction for(int x = 0; x < rotate; x++) { digitalWrite(stepPin,HIGH); delayMicroseconds(500); digitalWrite(stepPin,LOW); delayMicroseconds(500); } } } lastAngle = currentAngle; if (state == "Auto"){ mode = state; } } }

Code language: Arduino (arduino)

In this post I’m going to introduce you to the MIT App Inventor 2 software and I’m going to show you what you need to quickly getting started building Android apps that interact and control your Arduino.

Here’s the contents that are going to be covered in this post:

• Introducing MIT App Inventor 2
• Why MIT App Inventor 2 is a good choice?
• Accessing MIT App Inventor 2
• How to control Arduino with MIT App Inventor (Bluetooth)
• MIT App Inventor Overview
• Projects with MIT App Inventor
• Android Apps for Arduino with MIT App Inventor 2

Conclusions

In this paper, we compared the effectiveness of Scratch and App Inventor with regard to the learning of computational thinking concepts. In order to compare these languages, we initially proposed a novel rubric for assessing both Scratch and App Inventor projects in terms of computational thinking concept learning. Based on the rubric, we calculated the effectiveness scores of high-quality Scratch and App Inventor projects. Note while some projects were created by teachers or adults, most were made by young students, by themselves. The experimental results show that the effectiveness scores for Scratch and App Inventor projects are significantly different. More specifically, Scratch projects scored higher on average on Parallelism, Synchronization, and Flow Control, while App Inventor projects scored higher on average on User Interactivity and Data Representation. However, we also found that the overall scores for programs tend to increase as the number of lines of code increases and that the scores are highly dependent on the types (genres) of projects. Based on these results, we can conclude that if students learn both Scratch and App Inventor, they can improve their computational thinking skills in general, and that mastering a single programming language can also improve their overall computational thinking skills if they practice creating various types of large programs.

Our future work will take three directions. First, we would like to survey or interview groups of experts (such as teachers and computer scientists) with regard to the learning of computational thinking concepts through Scratch and App Inventor. It would be very useful to uncover the difference between the results obtained by selected projects (artefacts) and the results obtained through expert groups. Second, we want to prepare educational materials for these languages in order to develop students’ comprehensive computational thinking skills based on the rubric proposed in this study. In particular, we would like to focus on what types of projects could be taught to students in order to foster computational thinking more effectively. Finally, we want to implement a more general rubric that consists not only of block-based programming languages but also of text-based programming languages such as Python and JavaScript, as these text-based programming languages are also widely used for educational purposes.

Building the App – Example 1

Now we are ready to build the first example. We will start with the layout of the program. First we will add some HorizontalArrangements from the layout Palette and set their properties like the height, the width and the alignment to match our program desired look. Then from the UserInterface Palette we will add a ListPicker and attach an image to it. The ListPicker will be used for selecting the Bluetooth device to which our smartphone will connect.

Next we will add another HorizontalArrangements in which we will place a Label. This label will indicate whether the smartphone is connected or not to the Bluetooth module and that’s why we will set the initial text of this label to “Not Connected”. The next label will be used for displaying the status of the LED, whether is turned off or on. The initial state will be “LED: OFF”. Next we will add the two buttons, ‘Turn On’ and ‘Turn Off’ for controlling the LED. At this point it is good to rename the components so that we can easier recognize and use them in the Blocks editor later. What’s left now is to add the BluetoothClient which is a Non-visible component as well as a clock which will be used for the real time indication of the connection status.

MIT App Inventor Overview

Go to http://appinventor.mit.edu/explore/ and press Create Apps button.

Next, click on Start new project as shown in figure below.

You’ll be asked to give your project a name. As we’re just exploring the MIT App Inventor 2 features, you can name it test.

Click OK. Your project is automatically saved.

If you go to Projects > My Projects you can see all your saved projects.

Click on the project name to open the app builder.

Designer

You’ll be presented with the Designer tab as shown in the following figure.

At 1) you select whether you are on the Designer or in the Blocks Editor tab. With MIT App Inventor you have 2 main sections: Designer and Blocks. The designer gives you the ability to add buttons, add text, add screens and edit the overall app look.

The Blocks section allows you to create custom functionality for your app, so when you press the buttons it actually does something with that event.

2) The Palette contains the components to build the app design like buttons, sliders, images, labels, etc…

3) It’s the Viewer. This is where you drag the components to build the app look.

4) Components. You can see all the components added to your app and how they are organized hierarchically.

5) Properties. This is where you select your components’ properties like color, size and orientation.

Blocks Editor

Open the Blocks editor tab.

In the Blocks editor tab, you have several sections:

1) contains the built-in blocks for creating the app’s logic. This is what makes the app define the buttons functionalities, send commands to Arduino, connect to the Bluetooth module, etc. You have several blocks grouped by categories:

• Control: if/else statements, while loops, etc…

• Logic: True, False, equal, not equal, etc…
• Math: math operators.
• Text: blocks that deal with text.
• Lists: blocks for handling lists.
• Colors: blocks to handle colors, like choosing a color, make color and split colors.
• Variables: initialize variables, setting variables values, get variables values, etc…
• Procedures: procedures are like functions. A procedure is a sequence of code blocks with a given name. Later, you can call that sequence of blocks instead of creating the same long sequence.

Inside each group, you have blocks that you can drag to the Viewer 2). In the Viewer, you drag the blocks and join them in a specific way to make something happen.

We recommend that you navigate inside the blocks section and explore what’s inside. The blocks look like puzzle pieces that fit into each other or not. If you can’t do something with certain blocks, they won’t fit.

In the backpack 3) you save code blocks to use later. You move blocks to the dustbin 4) to delete them.

Blocks Editor

Now in the Blocks editor we are ready to give life to our program. From the left side we got all the blocks and function related to the previously added components.

We will start with the BluetoothList ListPicker. From there first we will add the ‘BeforePicking’ block and attach to it the ‘set Bluetooth Elements’ block. Then from the BluetoothClient blocks we will add the ‘BluetoothClient AddressesAndNames’ block. What this set of blocks will do is set a list of Bluetooth devices which are already paired with our phone so when we will click on the ListPicker “Connect Button” the list of all paired devices will show up.

Next we have to set what will happen after we will pick or select our particular Bluetooth module. From the BluetoothClient block we will add the ‘call BluetoothClient .Connect address’ block and add the block ‘BluetoothList Selection’ to it, which means that our phone will connect to the Bluetooth address that we have previously selected.

Next from the Clock blocks we will add the “.Timer” block. Within this block we will make the real time indication whether the phone is connected or not to the Bluetooth module using the “set Text” block of the label named “Connected”.

Next we need to give life to the two buttons. So when the “TurnOn_Button” will be clicked we will use the Bluetooth client function “Send1ByteNumber” to send a number to the Arduino Bluetooth module. In our case that’s the number 49 which corresponds to the character ‘1’ according to the ASCII table and that will turn on the LED. Right after that we will use the “ReceiveText” BluetoothClient function to receive the incoming String which is send back from the Arduino to the phone. This String is set to the “LED_Status” Label.

The same procedure goes for the “TurnOff_Button” where the sending number should be changed to 48 which corresponds to character ‘0’. What’s left now is to download and install the program on our smartphone. We can do that from the “Build” menu by either saving it to our computer and then transfer to our phone or scan a QR code for online download of the program. Here’s the demonstration of the example.

Here’s a download file of the above MIT App Inventor project:

Projects with MIT App Inventor

This was just a quick introduction to the MIT App Inventor. Now, its time to start building apps!

Here’s a list of our popular Arduino and MIT App Inventor projects:

• Android App – RGB LED with Arduino and Bluetooth
• Arduino – Control 2 DC Motors Via Bluetooth
• Control your Arduino with Voice Commands

Introducing MIT App Inventor 2

MIT App Inventor 2 is a simple and intuitive free service for creating Android applications. If you want to start with MIT App Inventor, you don’t need to download or install any program in your computer as the software is cloud-based, so you build the apps directly in your browser (Chrome, Mozilla, Safari, Internet Explorer, etc).

For instance, you only need an internet connection for building the apps.

Accessing MIT App Inventor 2

To access MIT App Inventor 2 go to http://appinventor.mit.edu/explore/ and press the orange Create Apps button.

To access the app builder, you need a Google account. Follow the on-screen steps to login into MIT App Inventor 2. After that, you’ll be presented with the following dashboard (we’ll cover how to use the dashboard in the MIT App Inventor 2 Overview section):

How to Control Arduino with MIT APP Inventor (Bluetooth)

To establish a connection between the Arduino and your Android app, you need a Bluetooth communication protocol. For that, you need a Bluetooth module.

The most common Bluetooth modules used with the Arduino are the HC‑05 bluetooth, HC-04 and HC-06.

For more information about the bluetooth module, you can check this blog post: Reviews – HC-05 Bluetooth Module

The Bluetooth module works with serial data. This means that the Arduino sends information and the Bluetooth module receives it via serial (and vice-versa).

The following figure explains how the information flows from the Android app to the Arduino.

Your smartphone sends information to the Bluetooth module via Bluetooth. Then, the Bluetooth module sends the information via serial communication to the Arduino. This flow also works the other way around: the Arduino sends information to the Bluetooth module that sends it to the smartphone via Bluetooth.

Unified Rubric for Assessing Both Scratch and App Inventor Projects

One of the barriers to making a unified rubric that can be used for assessing both Scratch and App Inventor is that each programming language has its own code blocks. For example, App Inventor has local file access blocks (TinyDB) while Scratch does not have these types of blocks. Moreover, while Scratch can create clones of sprites, App Inventor does not have a cloning block. Therefore, we create a novel unified rubric based on the common features of Scratch and App Inventor. We reused the category names of the computational thinking concepts used in Dr. Scratch and modify the detailed criteria by taking into account the common characteristics of Scratch and App Inventor.

Abstraction and Problem Decomposition. We calculate the Abstraction and Problem Decomposition scores based on the sprites, components, and procedures, because these elements are strongly related to how the program is organized. The “sprite” of Scratch is similar to the “component” of App Inventor. Without a sprite or a component, we do not execute most of the code blocks. Thus, we consider sprites to be the same as the components. We also consider “My Blocks” in Scratch to be identical to “procedures” in App Inventor, as we can define new command blocks with parameters using them. We did not give additional points to procedures that return a value, because unlike procedures, we cannot return values in My Blocks.

We give one point to projects that have more than one script and more than one sprite (component). If My Blocks or procedures are defined in a project, then the project received two points. We give three points to a project in which parameters are defined.

First, if two scripts begin at the time a program starts, we give one point to that program. Because a Clock is activated by default when its program starts, an App Inventor project receives one point if a Clock is used in it. By the same token, we assign one point if a Scratch project has two green flags in one sprite. Then, we assign two points to projects for which there could be multiple scripts that run at the same time in the middle of the program execution step. For example, when we touch an image sprite in an App Inventor project, both the “when ImageSprite touched” and the “when Canvas touched” events are invoked simultaneously. In this case, we assign two points to the project. Finally, we give three points to projects for which it is possible that one script will affect the behavior of another script due to their parallel execution.

Logical Thinking. The term “Logical Thinking” is closely related to conditionals and logic operators. Thus, we assign one point for projects that have “if” statements and two points for those that have “if–else” statements. If any of the logic operations (and/or/not) are used in a project, we assign three points to that project. Note we only consider explicit conditionals. For example, the GetValue command block of the TinyDB component has the “valueIfTagNotThere” parameter. We use this parameter value if the data that we want to find does not exist. Although this block implicitly exploits the concepts of the “if–else” statement, we do not assign two points for these cases because we are not certain as to whether the code writer intended to use the “else” statement.

Flow Control. This type of computational thinking concept is closely related to loops. We assign one point to projects that have a sequence of blocks because loops can be simulated by just repeating the statements. We give two points to projects that have simple loops, such as “Repeat,” “Forever” or “For each number from, to, by.” We ignore certain exceptional cases for the sake of simplicity; for example, some Scratch projects have numerous duplicate codes instead of loops, as a “Repeat” block slows down the execution time if Turbo Mode is not used. As another example, some App Inventor projects implement loops using the Clock component and variables. Finally, we assign three points to projects that have more advanced loop blocks.

User Interactivity. Obviously, User Interactivity is strongly related to events. While Scratch has seven types of event blocks, App Inventor has 204 types of event blocks. Thus, we decided to assign three points to projects that have more than four distinct user events. If there are three or four distinct user events, the project receives two points. A project receives one point if it has only one or two distinct user events.

Data Representation. Data are usually represented in terms of properties, variables or lists. We assign one point to projects that contain at least one block that modifies their properties. If projects define and use variables, then assign them two points. Note some App Inventor programs use the properties of components (mainly Text Labels) to represent variables. We decided to not assign two points to those projects if the variables are not explicitly defined for the sake of simplicity. Finally, if there is a user-defined list in a project, then we assign three points to that project.

Why MIT App Inventor is a good choice?

• MIT App Inventor 2 is intuitive and simple to use.
• You don’t have to be an expert in programming or design to build awesome apps that can do useful stuff.
• Creating the design is as easy as selecting and placing widgets in the smartphone screen.
• The code is done with drag and drop puzzle blocks.

Anyone can learn how to build their own apps with MIT App Inventor 2 with a few hours of practice.

Step 7: Recieve Data From Arduino

Now, you are not always sending data to the Arduino. Sometimes you want to get something back. In fact, if you want to have reliable connections, you should require something back. A parity character, if you will. Something that signals that all of the data was received and the arduino is ready to get more. In this case we use the letter ‘d.’ D is for Done. Now you could change your arduino code to send the value of a sensor or anything else. But it is good practice and much more reliable to send every data set with an signal character to show that all the data was sent and received.

To read this data being sent (‘d’) just again go through the bluetooth options until you find the type of data that you want to wait for. The character ‘d’ in this case is simply text in the form of a single byte, so we allow the scanning of only one Byte. If it is a “d” then we know that the arduino read the signal we sent and that we can send another.

MIT App Inventor

From the MIT App Inventor website we need to log in into the online building application by clicking the “Create apps!” button. In order to log in we need to have a Gmail account. Once we are logged in now we can create our first project. Here’s how the design window looks and now we can start building our application.

But before do that, we can connect our smartphone to this project so that we can see how the app is taking shape directly on our smartphone in real time. In order to do that first we have to download the MIT AI2 Companion app from the Play Store and install it on our smartphone. Then from the Connect menu from the online editor we will select AI Companion and a barcode will appear which we just need to scan it or insert the code into the smartphone app and the connection between the online editor and the smartphone app will be established.

So now for example, if we insert a button in the screen of the online editor, the button will appear in real time on the smartphone as well. Similar to this, if you don’t want to use your smartphone while building the app, you can install the Android Emulator on your computer and use in the same way. You can find more details how to set up the Emulator on their website.

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