Matrix led display controlled by Arduino and Android - the coding part

HI guys,

  hope you have enjoyed reading our last post about matrix led display. As we mentioned earlier, this post is going to be about coding Arduino and Android so we could use it to control our system...

 We can start with Arduino code. So, what is actually needed? Of course, because we use MAX7219 martix led drivers you guess we will use some code and libraries that are (closely) connected with this drivers. Very usefull page about that and our initial guide to get more information about Arduino coding was http://www.pjrc.com/teensy/td_libs_Matrix.html, so thanks to people who made this page. First, readers can get some basic info about hw parts and more important and more usefull they can find some basic about used libraries. Those are Matrix.h and Sprite.h.  About them, you can find more at http://wiring.org.co/reference/libraries/Matrix/index.html  and 

http://wiring.org.co/reference/libraries/Sprite/index.html . So, if you write any code based on those two libraries, it is good to start with this because some elementary code about almost every command is present on those links. So, let's see onde again picture of our system.

Now we will try to explaine most important parts of our Arduino code, and if anyone needs more explination, try to contact us via mail or better, write comment, and we will send our code. Get in mind that for  first couple lines of code - it is connected with bluetooth configuration and more about that you can find in our post about Bluetooth - http://arduinoandroid.blogspot.com/2011/11/post-number-2-work-version.html

ArduinoSolution

#include <NewSoftSerial.h> // Bluetooth library #include <Sprite.h>  // Sprite before Matrix #include <Matrix.h> // instance of Matrix class with Arduino digital pins we use for DIN, CLOCK and //LOAD, respectively //                     DIN, CLK, LOAD, #chips Matrix myLeds = Matrix(12, 11, 10, 3); byte byteNiz[200]; //  Array for readed characters int pokByte =0; // pointer for the currently read character int i=23; // column value from where characters are started moving on display byte proc;  //  character currently being worked with int maks=0; // total length of text that will rotate on display int razlika = 0; // this is actually maks - length of display(23, because 3 matrix //8x8) int citao = 0; // for 0, character is being read, for 1 just shown rotating on display int krajnjaPozicija = 23; // max column value of display (depends of number of led matrices) int bluetoothTx = 2;  // TX-O pin for bluetooth mate, Arduino D2 int bluetoothRx = 3;  // RX-I pin for bluetooth mate, Arduino D3 NewSoftSerial bluetooth(bluetoothTx, bluetoothRx); // instances of bluetooth, //will be used for receiving characters from android app ...                          ... // for every letter (or better), for every sing you want to see on display, define //instances of Sprite, set height and witdh...with red colour, we wanted to show //you what sign is specified...define this for every letter you need Sprite letter_A = Sprite(5, 7,   B01110,   B10001,   B10001,   B11111,   B10001,   B10001,   B10001 ); Sprite letter_B = Sprite(5, 7,   B11110,   B10001,   B10001,   B11110,   B10001,   B10001,   B11110 ); ... // // Setup function - being executed only once, when program is being //started void setup() {   Serial.begin(9600);  // Serial communication at 9600bps   bluetooth.begin(115200);  // BaudRate for Bluetooth module is 115200bps  bluetooth.print("$$$");  // Get into Bluetooth mode command mode   delay(100);  // Short delay, so Bluetooth can answer with CMD  bluetooth.println("U,9600,N");  // get back to 9600, because 115200 can be to fast for NewSoftSerial     bluetooth.begin(9600);  // baudrate for bluetooth modul now is 9600     bluetooth.print("$$$");   delay(100);   bluetooth.println("w");   delay(1000);   bluetooth.println("---");/ exit from command mode   // Finished configuration od BT mate     myLeds.clear();// clear led display    myLeds.setBrightness(15); // set value for Led brightness        Serial.begin(9600);   // niz u koji se smestaju karakteri se popuni nulama   for( int brojac=0; brojac<200; brojac++ )     byteNiz[brojac] = 0;     pokByte = 0;  } // loop function, repeats all the time while the program is running void loop() {   myLeds.clear();// to refresh the display        readLetter();//  function used for character reading    if( citao == 1 )        drawLetter(); // function for showing text on led display } // FUNCTION FOR READING CHARACTERS void readLetter() {  if ( bluetooth.available() > 0 )  { // set values on initial state    i=23;    maks = i; // current length of text, it will grow   citao = 0; // for 0 is reading , for 1 is drawLetter in loop()   pokByte = 0;          // while BT recieves characters, they are recieved and ready for work      while ( bluetooth.available() > 0 )      {        proc = bluetooth.read(); // recieved character is now in proc        byteNiz[ pokByte ] = proc; // put proc in recieved characters array        pokByte = pokByte+1; // set pointer for the new character          // for every recieved character increase length of the text          switch (proc)          {             case 'a' :             case 'A' :              maks = maks+6;             break;                         case 'b' :             case 'B' :              maks = maks+6;             break; ... // treba proveriti za svaki karakter od mogucih za ispis ...      razlika = maks - 23; // difference between text length and display length      citao = (citao+1)%2 ; // reading is finished and now text can be shown on display     }   else       citao = 1; // continue with showing old text if there is no new text   } //FUNCTION FOR SHOWING TEXT ON DISPLAY void drawLetter() {       if( i < 0-razlika+1 )  // if all text has passed on display     i = krajnjaPozicija; //  start again with showing text        int poz = i;   // temporary variable for showing text   // ispis procitanih slova   for( int brojac = 0; brojac <pokByte; brojac++ )   { // conditions that serve us for showing just letters that are on visiable //part of display    boolean uslov1 = poz >= -5 && poz < 24 ;    boolean uslov2 = (poz >=- 4) && (poz < 24 ) ;    boolean uslov3 = (poz >=- 2) && (poz < 24 ) ;    boolean uslov4 = (poz >=- 3) && (poz < 24 ) ;         // you get character, and depending on its value, you show adecvate //character on led display      switch( byteNiz[brojac] )    { // examples for letters (A,a) and (B,b)      case 'a' :      case 'A' :      if( uslov1 )          myLeds.write( poz , 0 , letter_A ); // show on display     poz = poz+6; // places needed for character + one blanco       break;       case 'b' : // examples for (B,b)       case 'B' :         if( uslov1 )         myLeds.write( poz , 0 , letter_B );     poz = poz+6; // places needed for character + one blanco ... ... ... i = i-1; move left for one position citao = 1;  // text continues to show on display     delay(225); // short delay that gives effect that text is moveing }

So, after Arduino code we need to say something about Android code. Once again, we needed to create Android application in which user brings in text, and via bluetooth sends it to led display. Also, we created virtual display on our Android device, that shows virtualy how text is going on the display (we will show that in pictures just a little later). So, because of Bluetooth usage, we needed to use, i think API 2.2 or above (but i'm preety sure that it is 2.2), because form this vrsion, Bluetooth is enabled. Here is the class diagram for the Arduino code, and we will try to explain most important parts of most important classes.

Class PocetnaStrana.java is responsable for the look of application when it starts.

PocetnaStrana.java

public class PocetnaStrana extends Activity implements OnCheckedChangeListener  // implements View.OnClickListener {       EditText tvTextZaReklamu ; // text field where text is being input       Button sendButton, prelaz;        RadioGroup rg; // choose text color for virtual display on ANdroid       String boja="red"  ; // default color is red          Context c;        String txt; ... ... ... // icinijalizacija promenljivih u metodi OnCreate() protected void onCreate(Bundle savedInstanceState)       {             // TODO Auto-generated method stub       super.onCreate(savedInstanceState);       setContentView(R.layout.prvapage);       c=this.getApplicationContext();       tvTextZaReklamu = (EditText) findViewById( R.id.editTextPolje );       sendButton = (Button) findViewById( R.id.buttonSendMessage );       rg = (RadioGroup) findViewById(R.id.radioGroup1);       prelaz = (Button)this.findViewById(R.id.bBTConn);       rg.setOnCheckedChangeListener(this);       // part of method to choose color public void onCheckedChanged(RadioGroup group, int checkedId)       {             switch( checkedId )             {               case R.id.radioRedBoja :                     this.boja="red";                     break;                           case R.id.radioGreenBoja :                     this.boja="green";                     break;    ... ... //  sendButton.setOnClickListener(new View.OnClickListener() {       @Override       public void onClick(View v)       {         txt = tvTextZaReklamu.getText().toString();       Bundle basket = new Bundle(); //pas the data to new activity       basket.putString("txt", txt); // put the data                     basket.putString("boja", boja); // pass the color of the text                               hand.post(tmp); //pass the data to threed which controls the Bluetooth                                               Intent a = new Intent(PocetnaStrana.this,LedDispleyCommercialActivity.class);       a.putExtras(basket); // put all data in basket       startActivity(a); // go to new activity ... ... ... // code for goint to activity connected with Vluetooth part of the code prelaz.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) {    Intent i = new Intent();    i.setClass(c, Settings.class);     startActivity(i);    } ... ... ... // Handler which controls sending to BT mate device public Handler hand = new Handler();     Runnable tmp = new Runnable()      {        public void run()        {try         {           outputStream=Singleton.remote_soket.getOutputStream();                        String send=txt;           byte[] bytesend = new byte[1024];           bytesend=send.getBytes();                             outputStream.write(bytesend);

   Here is the look of application when it starts

 If you click on button Bluetooth connection, it goes to :

When Bluetooth connection achieved, you click save and back to main menu and return to start page, so enter text and click send, and text is now sent to Arduino and starts rotating on Led display. The procudere and code for that is already described earlier in this post when we talked about Arduino code. Also, application has presentation of virtual led display where text is also rotated from left to right.

Now we will describe most important parts of code for that virtual text rotation.

LedDisplayCommercial.java

public class LedDispleyCommercialActivity extends Activity {   // atributi klase     private MotionRunner mRunner; // instance class MotionRunner     private int delay = 100; // delay speed     public void onCreate(Bundle savedInstanceState)     {         super.onCreate(savedInstanceState);         Bundle getBasket = getIntent().getExtras();                 // get the text and color from the start activity         String s = getBasket.getString("txt"); // get text         String boja = getBasket.getString("boja"); // get color         // inicijalizacija instance klase MotionRunner         mRunner = new MotionRunner(this  , s , boja );         setContentView(mRunner);         mRunner.startIt(delay); // start thread for drawing virtual display } // method for resuming activity  protected void onResume() {    super.onResume();    mRunner.startLooper(delay); } // method for stopping protected void onStop() {   super.onStop();   finish(); }

 Those are most important classes of Android application, so if anyone needs more information, write a comment and we will try to answer and help/solve the problem. In next posts we hope to set some videos ones who are interested may see how system actually works, and potential idea is to try to gather some other guys (and girls) from university who also worked with Arduino and try to make some video podcast about our projects.

See you soon,

  M&M team