Using android mobile to control arduino

Here is my android controlled arduino project. A simple app sends data through SPP over bluetooth and switches an LED on and off.

The circuit is just a bluetooth module, arduino UNO, LED, resistor and some wires.

The LED can be switched on using buttons as well as voice activation (anything that contains the word ‘on’,‘off’ or ‘blink’ - so saying ‘turn the LED on’ works as well as just uttering ‘on’).
I created the app using MIT app inventor and this project was created pretty much only to show how easy it is to write custom apps using the tool and interface with microcotrollers in this manner. One could use MIT app inventor to add more more features, such as using accelerometer or GPS data to control the LED, switching the state using text messages, web communication, not only send but also receive data, etc.
…well the point is - MIT app inventor is pretty cool and you should check it out

VIDEO OF IT → http://youtu.be/41MRGjdVIMQ




Here is the app for download → Loading...

and here is the source, you can upload it to MIT’s app inventor and modify as much as you want to → Loading...

Here is the arduino code

const int ledPin = 7;      // the pin that the LED is attached to
  byte serialA;
void setup()
{
  // initialize the serial communication:
  Serial.begin(19200);
  // initialize the ledPin as an output:
  pinMode(ledPin, OUTPUT);
}

void loop() {


  
      
      switch (serialA) {
    case 1:
      digitalWrite(ledPin, HIGH);
      break;
    case 2:
      digitalWrite(ledPin, LOW);
      break;
    case 3:digitalWrite(ledPin, HIGH);
      delay(100);
      digitalWrite(ledPin, LOW);
      delay(100);
     
      
  }
}
void serialEvent(){
serialA = Serial.read();
}

Could you share the AppInventor project?

Here is the source file -> http://speedy.sh/mDyAk/bluetoothforarduino-app-1.zip

As I mentioned on hackaday it won't be the exact copy as I improved it to react not only to 'BLINK' command but also 'FLASH' and 'CYCLE'... done that just because google voice search usually returns 'pink' or even 'd#ck' instead of BLINK :-D but apart from that it's the same

If you have any problems with downloading the files just let me know

This might be a noob question but what bluetooth module did you use?

I just gave this a try myself and it worked great. Now I am trying to receive data (an integer value) from the arduino instead of sending to it, but cant seem to figure out how…

Well it is a bit trickier.

Use a call bluetoothclient.receivetext and set th number of bytes to -1, which reads until delimiter byte is received.
Mmake sure you set the delimiter byte - I used ‘13’ which is carriage return… ohh you might find this useful → http://www.asciitable.com/index/asciifull.gif

What’s more, it’s seems there is no serial timout implemented yet and the app freezes if it doesn’t receive anything. To solve that I set up the app to first send a 1 byte number to the arduino, when arduino receives that it sends its data.

Here is an app I created to receive data from a 1 wire temperature sensor (ds18b20). I think if you upload it into the MIT app inventor you should be able to work this out and modify it.
http://speedy.sh/qscGe/bluetoothforarduino-app-temperaturereadings-1.zip

and arduino code (temperature sensor is connected to digital pin 2)

#include <OneWire.h>
int DS18S20_Pin = 2; //DS18S20 Signal pin on digital 2

//Temperature chip i/o
OneWire ds(DS18S20_Pin); // on digital pin 2


  byte serialA;
void setup()
{
  // initialize the serial communication:
  Serial.begin(19200);
  // initialize the ledPin as an output:
  pinMode(ledPin, OUTPUT);
}

void loop() {

  
 




  
 
     
    if (serialA == 49){float temperature = getTemp();
Serial.println(temperature); serialA = 0;

} 


}
  
  
float getTemp(){
//returns the temperature from one DS18S20 in DEG Celsius

byte data[12];
byte addr[8];

if ( !ds.search(addr)) {
//no more sensors on chain, reset search
ds.reset_search();
return -100;
}

if ( OneWire::crc8( addr, 7) != addr[7]) {
Serial.println("CRC is not valid!");
return -1000;
}

if ( addr[0] != 0x10 && addr[0] != 0x28) {
Serial.print("Device is not recognized");
return -1000;
}

ds.reset();
ds.select(addr);
ds.write(0x44,1); // start conversion, with parasite power on at the end

byte present = ds.reset();
ds.select(addr);
ds.write(0xBE); // Read Scratchpad


for (int i = 0; i < 9; i++) { 
data[i] = ds.read();
}

ds.reset_search();

byte MSB = data[1];
byte LSB = data[0];

float tempRead = ((MSB << 8) | LSB); 
float TemperatureSum = tempRead / 16;

return TemperatureSum;}


void serialEvent(){
serialA = Serial.read();
}

The code is a bit messy I admit but it does work

@kerimil

Thanks for sharing your code and work! I have now started trying to learn app inventor because of your post! I too wish to send and receive bluetooth data so, I am very interested in that!

kerimil: What's more, it's seems there is no serial timout implemented yet and the app freezes if it doesn't receive anything. To solve that I set up the app to first send a 1 byte number to the arduino, when arduino receives that it sends its data.

I wonder if you have to test for bytes available? In the Arduino it would be a test like if(Serial.available()){ Serial.read } .

In the code blocks you have a something that says BluetoothClient1BytesAvailableToReceive.............I think it should be combined with a if > 0 { read the byte }....or something like that.

P.S. I am tring to adapt your code to my purpose and I am learning while making the attempt. :)

cyclegadget: I wonder if you have to test for bytes available? In the Arduino it would be a test like if(Serial.available()){ Serial.read } .

In the code blocks you have a something that says BluetoothClient1BytesAvailableToReceive.............I think it should be combined with a if > 0 { read the byte }....or something like that.

Well yeah, but you can't have (Serial.available()){ Serial.read } all by itself - meaning the control structure block has to be attached to something else - ideally it should happen with no user input. The only thing I can think of is to have it inside Clock.timer block and set it to fire every 10 ms or so. That's not ideal but it might work.

I had had some problems when I tried to implement it. Though the idea might be ok. I might have messed up something else - it is possible I sent data more often than the app received them and that freezed the app because of the buffer. Well at least that's my understanding of it

Where did you get the bluetooth module?

it's a BTM222 module on a custom breakout board - kind of cool because it is a class 1 device - so the max range is not 10m but 100m :D I bought it from a local tinkerer who makes them - so I don't think you'd be able to get it

Though there are lots of such boards all over ebay - though most of them are class 2 (range ~10meter)

kerimil: I had had some problems when I tried to implement it. Though the idea might be ok. I might have messed up something else - it is possible I sent data more often than the app received them and that freezed the app because of the buffer. Well at least that's my understanding of it

I kept getting the same thing, its quite frustrating as my phone takes forever to recover! In my arduino code I just had Serial.println(...) in the loop and had my app to receive text every 1 second (with delimiter byte set to 13). I either get some odd values or it just crashes.

it works but only if serial data is received as often as it's sent... so your arduino code should send the data every 1 second

First of all THANKS, this was the project that I was waiting for. I do not understand very much the wiring connection, especially the bt connection, my lack. green wire: pin0 (arduino) - ? (bt) yellow wire: pin 7 (arduino) - led black wire: ? (arduino) - resistor - ? (bt) red wire: ? (arduino) - ? (bt)

and like in a loop I finish with End of all THANKS

Oh sorry I forgot to post wiring diagrams here. Now it should be a lot easier to understand.

If you can't see the pics just go here -> http://www.instructables.com/id/How-control-arduino-board-using-an-android-phone-a/

I found out how to send data from the app to cosm website

here is a video showing an example app as well as a brief explanation of how to use app inventor

You can download the app here >>
Download at SpeedyShare

Here you can download the source >>
http://speedy.sh/Vwwww/bluetoothAppCosmExampleTemperature.zip

Here is arduino code I used (note that you need OneWire library for it to work)

#include <OneWire.h>
int DS18S20_Pin = 2; //DS18S20 Signal pin on digital 2

//Temperature chip i/o
OneWire ds(DS18S20_Pin); // on digital pin 2



void setup()
{
  // initialize the serial communication:
  Serial.begin(19200);
  // initialize the ledPin as an output:

}

void loop() {


   float temperature = getTemp();
Serial.println(temperature); delay (250);

} 


float getTemp(){
//returns the temperature from one DS18S20 in DEG Celsius

byte data[12];
byte addr[8];

if ( !ds.search(addr)) {
//no more sensors on chain, reset search
ds.reset_search();
return -100;
}

if ( OneWire::crc8( addr, 7) != addr[7]) {
Serial.println("CRC is not valid!");
return -1000;
}

if ( addr[0] != 0x10 && addr[0] != 0x28) {
Serial.print("Device is not recognized");
return -1000;
}

ds.reset();
ds.select(addr);
ds.write(0x44,1); // start conversion, with parasite power on at the end

byte present = ds.reset();
ds.select(addr);
ds.write(0xBE); // Read Scratchpad


for (int i = 0; i < 9; i++) { 
data[i] = ds.read();
}

ds.reset_search();

byte MSB = data[1];
byte LSB = data[0];

float tempRead = ((MSB << 8) | LSB); 
float TemperatureSum = tempRead / 16;

return TemperatureSum;}

And here is the feed I created for the app → The feed is available here - https://cosm.com/feeds/118188

In order to send data from or to your own COSM feed you have to modify the URL as follows (parts that you have to fill in are in capital letters):

http://api.cosm.com/v2/feeds/YOUR FEED ID/datastreams/YOUR DATASTREAM ID.csv?key=YOUR API KEY&_method=put

Then copy and paste the URL into a QR code generator, generate a QR code and scan it using the app. You might as well use the feed I created for the app - it’s the default URL set in the app so you don’t have to enter it - it’s already there

If you have any questions feel free to ask them

When is necessary to use a level-shifter? some people use the 74HC4050N level shifter in conjunction with the btm222 module!

The module I got has a proper level shifter on it, but AFAIK one could improvise with zener diodes to achieve the same effect (not that level shifters are very expensive)

Tanks a lot Kerimil for your project vert helpfull. I tried to do the same without Voice recognising. The connection From my phone and Bluetooth device is ok, the wiring sure ok ( rx to dx and dx to rx). But nô serial data is send. On your sketch, you initialise serial communication with 19200 bauds. I think the Bluetooth deviçe should send is data at same speed. Where did you initialise serial data speed on Bluetooth device? Perhaps the problème comes From there. Tanks for your answer

Where did you initialise serial data speed on Bluetooth device?

Between the Bluetooth device and the phone, the serial data speed is solved during “pairing” of the device to the phone. At least this is my belief.