问用arduino和超声波hc 04传感器进行速度测量？

EN

/* 
by Claudiu Cristian 
*/ 

unsigned long time1; 
int photocellPin_1 = 0; // 1st sensor is connected to a0 
int photocellReading_1; // the analog reading from the analog port 
int photocellPin_2 = 1; // 2nd sensor is connected to a1 
int photocellReading_2; // the analog reading from the analog port 
int threshold = 700; //value below sensors are trigerd 
float Speed; // declaration of Speed variable 
float timing; 
unsigned long int calcTimeout = 0; // initialisation of timeout variable 

void setup(void) { 
// We'll send debugging information via the Serial monitor 
Serial.begin(9600); 
} 

void loop(void) { 
photocellReading_1 = analogRead(photocellPin_1); //read out values for sensor 1 
photocellReading_2 = analogRead(photocellPin_2); //read out values for sensor 2 
// if reading of first sensor is smaller than threshold starts time count and moves to             calculation function 
if (photocellReading_1 < threshold) { 
time1 = millis(); 
startCalculation(); 
} 
} 

// calculation function 
void startCalculation() { 
calcTimeout = millis(); // asign time to timeout variable 
//we wait for trigger of sensor 2 to start calculation - otherwise timeout 
while (!(photocellReading_2 < threshold)) { 
photocellReading_2 = analogRead(photocellPin_2); 
if (millis() - calcTimeout > 5000) return; 
} 
timing = ((float) millis() - (float) time1) / 1000.0; //computes time in seconds 
Speed = 0.115 / timing; //speed in m/s given a separation distance of 11.5 cm 
delay(100); 
Serial.print(Speed); 
Serial.print("\n"); 
}