volatile double a;
float checkdistance_9_10() {
digitalWrite(9, LOW);
delayMicroseconds(2);
digitalWrite(9, HIGH);
delayMicroseconds(10);
digitalWrite(9, LOW);
float distance = pulseIn(10, HIGH) / 58.00;
delay(10);
return distance;
}
void setup(){
a = 0;
pinMode(9, OUTPUT);
pinMode(10, INPUT);
Serial.begin(9600);
pinMode(2, OUTPUT);
}
void loop(){
while (true) {
a = checkdistance_9_10();
Serial.println(a);
if (a > 20 && a < 120) {
digitalWrite(2,HIGH);
delay(1000);
digitalWrite(2,LOW);
}
delay(1000);
}
checkdistance_9_10();
} 

串口：