fzj_msg_sender_arduino

gistfile1.txt

/*
  fzj_msg_sender
  converts bytes into binary digits and sends them out
  
  by Fernando Zamora
 */

const int MAX_MESSAGE_BIT_SIZE = 128;  //nice even sixteen bytes of data
const int MAX_MESSAGE_CHAR_SIZE = 16;  //nice even sixteen bytes of data
const int DELAY = 1;
// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin 13 as an output.
  pinMode(13, OUTPUT);
  Serial.begin(9600);
  
}

// the loop function runs over and over again forever
void loop() {
   transmitMessage();
}

void transmitMessage(){
 
   char message[] = "hello world\0";
   int encodedMessage[MAX_MESSAGE_BIT_SIZE]={0};
   encodeMessage(message, encodedMessage);
   transmitMessage(encodedMessage);   
}

void runTests(){  
  testEncoding();
  testTransmission();
  testDecodeByte();
  testDecodeMessage();
}


/***********************************************

    TESTS FOR TRANSMISSION
    
***********************************************/
void testTransmission(){
   Serial.println("");
   Serial.println("**** TESTING TRANSMIT ****");
   Serial.println("  transmitting \"hello\" ");
   Serial.println("");
   char message[] = "hello\0";
   int encodedMessage[MAX_MESSAGE_BIT_SIZE]={0};
   encodeMessage(message, encodedMessage);
   transmitMessage(encodedMessage);
}

/************************************************

    TESTS FOR ENCODING

*************************************************/
void testEncoding(){

   Serial.println("");
   Serial.println("**** TESTING ENCODING ****");
   Serial.println("  encoding \"hello\" ");
   Serial.println("");
   char message[] = "hello\0fool";
   int encodedMessage[MAX_MESSAGE_BIT_SIZE]={0};
   encodeMessage(message, encodedMessage);
   displayFullEncodedMessage(encodedMessage); 
   Serial.println("");
   Serial.println("*** TEST ENCODING IS COMPLETE *****");
   Serial.println("");
   delay(4000);  
}

void displayFullEncodedMessage(int* encodedMessage){

   for(int i = 0; i < MAX_MESSAGE_BIT_SIZE; i++){
      if(i%8==0){
        Serial.println(""); 
      }
      Serial.print(encodedMessage[i]);
   }  
}

void displayBitArray(byte val, int* bitArray){
  
  Serial.println("");
  Serial.println(val);
  Serial.println((char)val);
  for(int i = 0; i < 8; i++){
    Serial.print(bitArray[i]);
  } 
  Serial.println("");
}

void testDecodeByte(){
  
     Serial.println("**************TESTING DECODING BYTE**********");
     Serial.println("");
     
     for(int i = 0; i <24;i++){
       int bitArray[8] = {0};
       
       encodeByte(i, bitArray);
      
       int result = decodeByte(bitArray);
       
       Serial.println("");
       Serial.print("DECODED: ");       
       Serial.print(result);
       Serial.println("");
     }
     
     Serial.print("");
     Serial.println("*******************DECODING********************");  
}


void testDecodeMessage(){
  
   Serial.println("");
   Serial.println("**** TESTING DECODING ****");
   Serial.println("  encoding and then decoding \"hello\" ");
   Serial.println("");
   
   char message[] = "decoded hello\0";
   int encodedMessage[MAX_MESSAGE_BIT_SIZE]={0};
   char decodedMessage[MAX_MESSAGE_CHAR_SIZE]={0};
   
   encodeMessage(message, encodedMessage);
   decodeMessage(encodedMessage, decodedMessage);
   
   Serial.println("DECODED MESSAGE: ");
   Serial.println(decodedMessage); 
   Serial.println("");
   Serial.println("*** TEST DECODING IS COMPLETE *****");
   Serial.println("");
   delay(4000);  
}

/**********************************************************

   ENCODE API SECTION

***********************************************************/

//converts bytes to bit array
//so it would take the value 5 for example 
//and convert it to the array with values 0000 0101
//it uses bitShifting so that only the last byte has to be tested
void encodeByte(byte byteValue, int* values){
  int tempValue = byteValue;
  
  for(int i = 7; i > -1; i--){
        values[i] = tempValue & 1;
        tempValue = tempValue >> 1; 
  } 
}


/*

   decodeByte converts the 8 element array of 1's and0's 
   and turns it into a single numeric value
*/
int decodeByte(int* bitArray){
 
  int tempValue = 0;
  int result = 0;
  
  for(int i = 7; i > -1; i--){
        tempValue = bitArray[i];     
     
        //shift the bit to give it the appropriate positional value   
        tempValue = tempValue << (7-i);        
        
        //add that value to the running total
        result = result + tempValue; 
  }
  
  return result;  
}

/*
   Encodes the string in message into the encodedMessage
   the message is in ascii characters
   the encoded message is an array of 0's and 1's

*/
void encodeMessage(char* message, int* encodedMessage){
   
   //loop through all the characters in the message array
   //e.g. h e l l o in the message "hello"
   for(int i = 0; i < MAX_MESSAGE_CHAR_SIZE; i++){
     
      if((byte)message[i] == 0){
        break;  
      }
      
      int bitArray[8];  //holder for the individual bits
      encodeByte((byte)message[i], bitArray);
      append(encodedMessage, i*8, bitArray);
   }
}


/*
   decodeMessage takes the array of 1's and 0's in encodedMessage
   and converts to a string into the decodedMessage

*/
void decodeMessage(int* encodedMessage, char* decodedMessage){
   
  for(int i = 0; i < MAX_MESSAGE_CHAR_SIZE; i++){
     
       int bitArray[8] = {0};
       
       //every 8 elements creates a single byte to decode
       int startingIndex = i*8;
       
       for(int j=0; j<8; j++){
          bitArray[j] = encodedMessage[startingIndex+j]; 
       }
       
       //decode the byte and append it to the decoded message
       decodedMessage[i] = (char)decodeByte(bitArray);        
  }
 
  //the last element of the message is reserved for the terminating character
  decodedMessage[MAX_MESSAGE_CHAR_SIZE-1] = '\0';
}

//since characters are encoded one byte at a time
//this append function takes care of appending each 8 bit array
//to a full message bit array
void append(int* encodedMessage, int startingIndex, int* bitArray){
 
  for(int i=0; i < 8; i++){
     encodedMessage[startingIndex+i] = bitArray[i]; 
  }  
}

/**********************************************************

   TRANSMIT/RECEIVE API SECTION

***********************************************************/

void transmitMessage(int* encodedMessage){

     int onOrOff[2] = {LOW,HIGH};
     
     //transmit start packet
     //three bytes of alternating 0's and 1's
     for(int i = 0; i < 3; i++){
        for(int j=0; j < 4; j++){
           digitalWrite(13, LOW);
           delay(DELAY);
           digitalWrite(13, HIGH);
           delay(DELAY);  
        }       
     }
     
     //end of packet off for 1 byte
     for(int i = 0; i < 8; i++){
        digitalWrite(13, LOW);
        delay(DELAY); 
     }     
     
     //send message
     for(int i = 0; i < MAX_MESSAGE_BIT_SIZE; i++){
         digitalWrite(13, onOrOff[encodedMessage[i]]);
         delay( DELAY );
     } 
 
     delay(DELAY*24);    
}

updated sketch that also decodes the messages now