为什么digitalWrite(a，低)；不工作在7段发光二极管？

Question

int a = 3;
int b = 4;
int c = 7;
int d = 6;
int e = 5;
int f = 2;
int g = 1;
void setup(){
pinMode(a,OUTPUT);
pinMode(b,OUTPUT);
pinMode(c,OUTPUT);
pinMode(d,OUTPUT);
pinMode(e,OUTPUT);
pinMode(f,OUTPUT);
pinMode(g,OUTPUT);
}
void loop(){
digitalWrite(a, LOW);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(g, LOW);
digitalWrite(e, LOW);
delay(1000);
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, LOW);
digitalWrite(g, HIGH);
digitalWrite(e, HIGH);
}

我用的是7段LED。基本上，我想用1秒间隔来显示数字1-5，但是似乎digitalWrite低不起作用。它并没有停止输出。

Answer 1

当Arduino到达loop()的末尾时，它立即再次调用loop()。两次通话之间没有任何延误。因此，第一组digitalWrite()的值将很快覆盖第二组的值。您将只能看到显示上的第一个值。如果你想看到第二组，你应该在它后面放一个delay(1000)。

要用1秒间隔显示数字1-5，您可以编写如下内容：

int a = 3;
int b = 4;
int c = 7;
int d = 6;
int e = 5;
int f = 2;
int g = 1;

void setup()
{
  pinMode(a, OUTPUT);
  pinMode(b, OUTPUT);
  pinMode(c, OUTPUT);
  pinMode(d, OUTPUT);
  pinMode(e, OUTPUT);
  pinMode(f, OUTPUT);
  pinMode(g, OUTPUT);
}

void loop()
{
  digitalWrite(a, LOW);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  digitalWrite(d, LOW);
  digitalWrite(e, LOW);
  digitalWrite(f, LOW);
  digitalWrite(g, LOW);

  delay(1000);

  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  digitalWrite(c, LOW);
  digitalWrite(d, HIGH);
  digitalWrite(e, HIGH);
  digitalWrite(f, LOW);
  digitalWrite(g, HIGH);

  delay(1000);

  digitalWrite(a, HIGH);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  digitalWrite(d, HIGH);
  digitalWrite(e, LOW);
  digitalWrite(f, LOW);
  digitalWrite(g, HIGH);

  delay(1000);

  digitalWrite(a, LOW);
  digitalWrite(b, HIGH);
  digitalWrite(c, HIGH);
  digitalWrite(d, LOW);
  digitalWrite(e, LOW);
  digitalWrite(f, HIGH);
  digitalWrite(g, HIGH);

  delay(1000);

  digitalWrite(a, HIGH);
  digitalWrite(b, LOW);
  digitalWrite(c, HIGH);
  digitalWrite(d, HIGH);
  digitalWrite(e, LOW);
  digitalWrite(f, HIGH);
  digitalWrite(g, HIGH);

  delay(1000);
}

下面的代码是一种更有效的方法来做同样的事情：

int a = 3;
int b = 4;
int c = 7;
int d = 6;
int e = 5;
int f = 2;
int g = 1;

void display(bool a_val, bool b_val, bool c_val, bool d_val, bool e_val, bool f_val, bool g_val)
{
  digitalWrite(a, a_val);
  digitalWrite(b, b_val);
  digitalWrite(c, c_val);
  digitalWrite(d, d_val);
  digitalWrite(e, e_val);
  digitalWrite(f, f_val);
  digitalWrite(g, g_val);
  delay(1000);
}

void setup()
{
  pinMode(a, OUTPUT);
  pinMode(b, OUTPUT);
  pinMode(c, OUTPUT);
  pinMode(d, OUTPUT);
  pinMode(e, OUTPUT);
  pinMode(f, OUTPUT);
  pinMode(g, OUTPUT);
}

void loop()
{
  display(LOW,  HIGH, HIGH, LOW,  LOW,  LOW,  LOW);
  display(HIGH, HIGH, LOW,  HIGH, HIGH, LOW,  HIGH);
  display(HIGH, HIGH, HIGH, HIGH, LOW,  LOW,  HIGH);
  display(LOW,  HIGH, HIGH, LOW,  LOW,  HIGH, HIGH);
  display(HIGH, LOW,  HIGH, HIGH, LOW,  HIGH, HIGH);
}