请各位帮忙看一下，关于setup 和 millis 函数的问题

诶咦唉哦呦

问题参见代码中的注释，why always print 0?

1. //run horse light 2013.11.10
   
2. 
   
3. byte ledPin[] = {5,6,7,8,9,10,11,12};
   
4. int ledDelay = 65;
   
5. int ledDirection = 1;
   
6. int currentLed = 0;
   
7. unsigned long changeTime;
   
8. 
   
9. void setup(){
   
10.   Serial.begin(9600);
    
11.   for(int i = 0;i<8;i++){
    
12.     pinMode(ledPin[i],OUTPUT);
    
13.   }
    
14.   changeTime = millis();
    
15. }
    
16. 
    
17. void loop(){
    
18.   //Serial.println("hello");
    
19.   int ival = millis()-changeTime;
    
20.   Serial.println(ival);//why always print 0?
    
21.   if((millis()-changeTime)>ledDelay){
    
22.     Serial.println("hello");
    
23.     changeLights();
    
24.   }
    
25.   changeTime = millis();
    
26. }
    
27. void changeLights(){
    
28.   for(int i = 0;i < 8;i++){
    
29.     digitalWrite(ledPin[i],LOW);
    
30.   }
    
31.   digitalWrite(currentLed,HIGH);
    
32.   currentLed += ledDirection;
    
33.   
    
34.   if(currentLed == 9){
    
35.     ledDirection = -1;  
    
36.   }
    
37.   if(currentLed == 0){
    
38.     ledDirection = 1;
    
39.   }
    
40. }

复制代码

万马奔腾

17.void loop(){

18.  //Serial.println("hello");

19.  int ival = millis()-changeTime;

20.  Serial.println(ival);//why always print 0?

21.  if((millis()-changeTime)>ledDelay){

22.    Serial.println("hello");

23.    changeLights();

24.       changeTime = millis();  }

25.

26.}
照你的程序，肯定是0撒？

林定祥

25行后,接下来是19行,应该等于0.不知道想干什么?

飞翔的红猪

void loop(){

  //Serial.println("hello");

  int ival = millis()-changeTime;

  Serial.println(ival);//why always print 0?

  if((millis()-changeTime)>ledDelay){
    changeTime = millis();
    Serial.println("hello");

    changeLights();

  }
}

kwleung

millis() = ms++ =1/1000(s)
Serial.begin(9600); = 1 / 9600 (s)

Arduino send "0" to pc, less then 1ms,

所以 是 0