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const int pingPin = 7; | |
const int ledPin = 13; | |
int ledState = LOW; | |
unsigned long interval; | |
unsigned long previousMillis = 0; | |
void setup() { | |
pinMode(ledPin, OUTPUT); | |
} | |
void loop() { | |
long duration = ping(); | |
long inches = microsecondsToInches(duration); | |
interval = inches * 100; | |
// check to see if it's time to blink the LED; that is, if the | |
// difference between the current time and last time you blinked | |
// the LED is bigger than the interval at which you want to | |
// blink the LED. | |
unsigned long currentMillis = millis(); | |
if (currentMillis - previousMillis >= interval) { | |
// save the last time you blinked the LED | |
previousMillis = currentMillis; | |
// if the LED is off turn it on and vice-versa: | |
if (ledState == LOW) { | |
ledState = HIGH; | |
} else { | |
ledState = LOW; | |
} | |
// set the LED with the ledState of the variable: | |
digitalWrite(ledPin, ledState); | |
} | |
} | |
long ping() { | |
// The PING))) is triggered by a HIGH pulse of 2 or more microseconds. | |
// Give a short LOW pulse beforehand to ensure a clean HIGH pulse: | |
pinMode(pingPin, OUTPUT); | |
digitalWrite(pingPin, LOW); | |
delayMicroseconds(2); | |
digitalWrite(pingPin, HIGH); | |
delayMicroseconds(5); | |
digitalWrite(pingPin, LOW); | |
// The same pin is used to read the signal from the PING))): a HIGH | |
// pulse whose duration is the time (in microseconds) from the sending | |
// of the ping to the reception of its echo off of an object. | |
pinMode(pingPin, INPUT); | |
return pulseIn(pingPin, HIGH); | |
} | |
long microsecondsToInches(long microseconds) { | |
// According to Parallax's datasheet for the PING))), there are | |
// 73.746 microseconds per inch (i.e. sound travels at 1130 feet per | |
// second). This gives the distance travelled by the ping, outbound | |
// and return, so we divide by 2 to get the distance of the obstacle. | |
// See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf | |
return microseconds / 74 / 2; | |
} | |
long microsecondsToCentimeters(long microseconds) { | |
// The speed of sound is 340 m/s or 29 microseconds per centimeter. | |
// The ping travels out and back, so to find the distance of the | |
// object we take half of the distance travelled. | |
return microseconds / 29 / 2; | |
} |
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