Stepper motor control x bluetooth and app

1#define pin2  2
2#define pin3  3
3#define pin4  4
4#define pin5  5
5#define retardo 2   
6
7char caracter;
8String cadena; 
9float pasos = 0;
10int datos_serial = 0;
11
12void setup() {
13  pinMode(pin2, OUTPUT);
14  pinMode(pin3, OUTPUT); 
15  pinMode(pin4, OUTPUT); 
16  pinMode(pin5, OUTPUT);
17  Serial.begin(57600); //Velocidad del módulo bluetooth
18}
19
20void loop() {
21  while (Serial.available()) {  
22    delay(3);                  
23    char c = Serial.read(); 
24    cadena += c;        
25  }
26 
27  if (cadena.length() >0) { 
28  
29   Serial.println(cadena.toInt());  
30    datos_serial = cadena.toInt();
31    
32  }
33  while(datos_serial>pasos){
34             
35         atras();
36         delayMicroseconds(40);
37         pasos = pasos + 1;
38    
39  }
40 while(datos_serial<pasos){
41         
42          adelante();
43          delayMicroseconds(40);
44          pasos = pasos - 1;
45    
46  }
47  
48  if (cadena == "SET"){
49    pasos = 0;
50    datos_serial = 0;
51    }
52 
53  cadena=""; 
54}
55void paso1(){
56  digitalWrite(pin2, HIGH); 
57  digitalWrite(pin3, HIGH); 
58  digitalWrite(pin4, LOW); 
59  digitalWrite(pin5, LOW); 
60}
61void paso2(){
62  digitalWrite(pin2, LOW); 
63  digitalWrite(pin3, HIGH);
64  digitalWrite(pin4, HIGH); 
65  digitalWrite(pin5, LOW); 
66}
67void paso3(){
68  digitalWrite(pin2, LOW); 
69  digitalWrite(pin3, LOW); 
70  digitalWrite(pin4, HIGH);
71  digitalWrite(pin5, HIGH); 
72}
73void paso4(){
74  digitalWrite(pin2, HIGH); 
75  digitalWrite(pin3, LOW); 
76  digitalWrite(pin4, LOW); 
77  digitalWrite(pin5, HIGH); 
78}
79void pasoApagado(){
80  digitalWrite(pin2, LOW); 
81  digitalWrite(pin3, LOW); 
82  digitalWrite(pin4, LOW); 
83  digitalWrite(pin5, LOW); 
84}
85
86
87void adelante(){
88  paso1();
89  delay(retardo);
90  paso2();
91  delay(retardo);
92  paso3();
93  delay(retardo);
94  paso4();
95  delay(retardo);
96}
97
98void atras(){
99  paso3();
100  delay(retardo);
101  paso2();
102  delay(retardo);
103  paso1();
104  delay(retardo);
105  paso4();
106  delay(retardo);
107}