src/main.cpp

 #include <Arduino.h>
-//ver se os 15 fazem interferencia 
-
 
 #define MASTER_ADDR 15
 #define SLAVE1_ADDR 13
@@ -15,8 +13,6 @@ int lastButtonState2 = 0;
 uint8_t getData = 0;
 uint8_t *data =0;
 
-
-
 #define LED_PIN   13
 #define ADDR3_PIN 11
 #define ADDR2_PIN 10
@@ -27,22 +23,23 @@ uint8_t *data =0;
 #define WREN_PIN  2
 #define FOSC 16000000
 
-
 void asynch9_init(long BAUD) {
   // put your code here, to setup asynchronous serial communication using 9 bits:
   
   unsigned int ubrr = (FOSC/(16*BAUD))-1;
   /*Set baud rate */
-  UBRR0H = (unsigned char)(ubrr>>8); //shift para por os bits mais signicativos 
-  UBRR0L = (unsigned char)ubrr; // 8 bits menos significativos
+  UBRR0H = (unsigned char)(ubrr>>8);  
+  UBRR0L = (unsigned char)ubrr; // 8 LSB
   
   /*Set transmitter*/
   if(ADDR == MASTER_ADDR){
     UCSR0B |= (1<<TXEN0);
+    digitalWrite(WREN_PIN,HIGH); // to allow master transciever to send
   }
   else /*Set Receiver*/{
     UCSR0B |= (1<<RXEN0);
-    UCSR0A |= (1<<MPCM0); // multi processor communication mode- permite receber só os addr
+    UCSR0A |= (1<<MPCM0); // multi processor communication mode- allows recieving addr
+    digitalWrite(WREN_PIN,LOW);  //so that slaves transciever can recieve
   }
   /*frame format 9 bits of data*/  
   UCSR0C |= (3<<UCSZ01);
@@ -76,6 +73,7 @@ void send_data(uint8_t data) {
 
 uint8_t get_data(uint8_t *data) {
   // put your code here, to receive a data byte using multi processor communication mode:
+  
   unsigned char resh;
   /* Wait for data to be received */
   while (!(UCSR0A & (1<<RXC0)));
@@ -87,6 +85,12 @@ uint8_t get_data(uint8_t *data) {
 
   /* Filter the 9th bit, then return */
   resh = (resh >> 1) & 0x01;
+
+  if(resh == 1 && ADDR == *data){ // if it is the respective address
+      UCSR0A &= ~(1<<MPCM0); //to start "listening" data frames
+  }else if(resh == 1 && ADDR != *data){
+      UCSR0A |= (1<<MPCM0); //if it's not the respective address keep listening "addr"
+    }
   return resh;
    
 }
@@ -106,16 +110,7 @@ void setup() {
   pinMode(WREN_PIN, OUTPUT);
   digitalWrite(LED_PIN,LOW);
 
-  
-
-  
-
-  ADDR = (digitalRead(ADDR3_PIN)<<3) | (digitalRead(ADDR2_PIN)<<2) | (digitalRead(ADDR1_PIN)<<1) | (digitalRead(ADDR0_PIN)) ;
-  
-  if(ADDR == MASTER_ADDR){
-    digitalWrite(WREN_PIN,HIGH); // para o transciever do master possa enviar
-  }else 
-    digitalWrite(WREN_PIN,LOW);  //para os slaves receberem 
+  ADDR = (digitalRead(ADDR3_PIN)<<3) | (digitalRead(ADDR2_PIN)<<2) | (digitalRead(ADDR1_PIN)<<1) | (digitalRead(ADDR0_PIN)) ; 
   asynch9_init(BAUD);
 }
 
@@ -161,6 +156,7 @@ void loop() {
         }
       }
     else if(buttonState2 == 1){
+      
         if(last_ADDR == SLAVE2_ADDR){
           send_data(0);
         } else { 
@@ -175,16 +171,8 @@ void loop() {
   }
   //slaves
   if(ADDR == SLAVE1_ADDR || ADDR == SLAVE2_ADDR){ 
-    digitalWrite(WREN_PIN,LOW); // Para que os transceivers (os slaves) possam receber 
     getData = get_data(data);
-
-    if(getData == 1 && ADDR == *data){// se for o endereço
-      UCSR0A &= ~(1<<MPCM0); //para comecar a "ouvir" data framees
-    }else if(getData == 1 && ADDR != *data){
-      UCSR0A |= (1<<MPCM0); //senao for o  seu endereco continuar a ouvir "addr"
-    }
-  
     if(getData==0)
-      digitalWrite(LED_PIN,*data);
+      digitalWrite(LED_PIN,*data); 
   }
 }