Arduino输入波动

Question

通过以下代码，我得到了如下所示的日志。这是为什么？

int analogPin = 5;
int val = 0;

void setup(void) {
   Serial.begin(9600);
}

void loop(void) {
   val = analogRead(analogPin);
   Serial.print("Analog reading = ");
   Serial.println(val);   
}

结果:

Analog reading = 998
Analog reading = 981
Analog reading = 511
Analog reading = 159
Analog reading = 24
Analog reading = 108
Analog reading = 439
Analog reading = 946
Analog reading = 1023
Analog reading = 420
Analog reading = 116
Analog reading = 25
Analog reading = 151
Analog reading = 542
Analog reading = 997
Analog reading = 982
Analog reading = 513
Analog reading = 161
Analog reading = 25
Analog reading = 107
Analog reading = 437
Analog reading = 945
Analog reading = 1023
Analog reading = 421
Analog reading = 117
Analog reading = 25
Analog reading = 150
Analog reading = 541
Analog reading = 997
Analog reading = 983
Analog reading = 515
Analog reading = 162
Analog reading = 25
Analog reading = 107
Analog reading = 437
Analog reading = 945
Analog reading = 1023
Analog reading = 422
Analog reading = 117
Analog reading = 25
Analog reading = 149
Analog reading = 540
Analog reading = 997
Analog reading = 983
Analog reading = 516
Analog reading = 162
Analog reading = 25
Analog reading = 107
Analog reading = 436
Analog reading = 945
Analog reading = 1023
Analog reading = 422
Analog reading = 117
Analog reading = 25
Analog reading = 150
Analog reading = 540
Analog reading = 998
Analog reading = 982
Analog reading = 516
Analog reading = 162
Analog reading = 25
Analog reading = 108
Analog reading = 437

结果只是噪音吗？

只要插入电缆，我就会看到以下模式:

Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 72
Analog reading = 447
Analog reading = 1023
Analog reading = 1023
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 118
Analog reading = 849
Analog reading = 1023
Analog reading = 835
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 40
Analog reading = 401
Analog reading = 1023
Analog reading = 1023
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 0
Analog reading = 89
Analog reading = 475
Analog reading = 1023
Analog reading = 1023

那是我的心跳吗？？？不知道什么会对空引脚产生如此大的影响。

Answer 1

是的，未连接的模拟引脚产生随机噪声是很正常的。来自documentation (强调我的):

If it is important for a sequence of values generated by random() to differ, on subsequent executions of a sketch, use randomSeed() to initialize the random number generator with a fairly random input, such as analogRead() on an unconnected pin.

关于您在插入电缆时看到的值，它们是否有意义取决于您输入引脚的信号。如果存在一些差异，可能值得使用示波器查看信号。

另请参阅 How come analogRead reads oscillating values from 0 to 1023 when no actual input is present?