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May 14, 2020 08:09
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// ************************************************* | |
// SR04 Ultrasonic Distance Sensor | |
// time to distance conversion is | |
// divide by 2 (both ways to the obstical and back) | |
// divide by sonic constant 29.1 | |
#define TRIGGER_PIN 3 | |
#define ECHO_PIN 2 | |
#define SC_MM 5.82 | |
#define SC_CM 58.2 | |
#define MAX_DUR 300 * 58.2 // ~3m in dur | |
#define MIN_DUR 2 * 58.2 // ~2cm in dur | |
#define TO_SMALL -1 | |
#define TO_BIG -2 | |
#define INT_TO_SMALL -3 | |
/** get duration */ | |
long getDur(int interval){ | |
if(interval < 1) return -3; | |
long dur=0; | |
for(int i = 0; i < interval; i++ ){ | |
// init sensor | |
digitalWrite(TRIGGER_PIN, LOW); | |
delayMicroseconds(3); | |
noInterrupts(); | |
// start 10 us pulse | |
digitalWrite(TRIGGER_PIN, HIGH); | |
delayMicroseconds(10); | |
digitalWrite(TRIGGER_PIN, LOW); | |
dur += pulseIn(ECHO_PIN, HIGH); // determine the time | |
interrupts(); | |
} | |
dur /= interval; | |
if(dur > MAX_DUR ) { return TO_BIG;} | |
// else if (dur < MIN_DUR){ return TO_SMALL;} | |
return dur; | |
} | |
void initDist(){ pinMode(TRIGGER_PIN, OUTPUT); pinMode(ECHO_PIN, INPUT);} | |
/** get the distance in centi meter*/ | |
double getDistCM(long dur){ return (dur / SC_CM);} | |
/** get the distance in milli meter*/ | |
long getDistMM(long dur) { return (dur / SC_MM);} | |
// ************************************************* | |
void setup(){ | |
Serial.begin(9600); | |
while(!Serial){delay(1);} // wait until the serial is ok (only for Leonardo) | |
initDist(); | |
} | |
void loop (){ | |
Serial.print("Current distance is: "); | |
long dur = getDur(5); | |
if(dur > 0) Serial.println(getDistCM(dur)); | |
else if( dur == TO_BIG) Serial.println("TO FAR"); | |
else if( dur == TO_SMALL) Serial.println("TO NEAR"); | |
delay(1000); // wait a second | |
} |
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