File content as of revision 0:4354437a1033:

#include "mbed.h"
#include <string>

#define node_id (0x01)
#define gateway_id (0xAA)
#define tx (PA_9)
#define rx (PA_10)

Serial xb(tx, rx);
Serial pc(D1, D0);

//string node_id = "01";
//string gateway_id = "AA"

// function declarations
void read_data(char* message);

/*
void readString(std::string& result, std::size_t& size) {
    results.clear();
    char data_in;
    while(xb.readable()){
        result.append(xb.getc());
        
    }
}
*/
int main() {
    pc.printf("echo!!\n");
    // initialize read data chars
    char pc_data = 'e';
    
    char buffer[128];
    char message[16];
    
    while(true){
        if(pc.readable()){
            pc_data = pc.getc();
            pc.printf("%c", pc_data);
            xb.printf("%c", pc_data);
        }
        
        if(xb.readable()){
            xb.gets(buffer, 4);
            pc.printf("%s", buffer);
                      
        }
    }
}

void read_data(char* message){
    int i = 0;
    
    while(xb.readable()){
        message[i] = xb.getc();
        pc.printf("%c", message[i]);
        wait(0.1);
    }
    
    pc.printf("%s", message);
}