jeremylindsayni / bifrost.arduino.sensors.hcsr04 Goto Github PK
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License: MIT License
Library and example for the HCSR04 distance sensor
License: MIT License
line 44 of hcsr04.cpp:
// Given the speed of sound in air is 332m/s = 3320cm/s = 0.0332cm/us).
hcsr04.cpp includes HCSR04.h instead of hcsro4.h
Hi Jeremy,
Many thanks for producing this library!
Found a bug, here is the explanation and the fix.
echoInMicroseconds() function has while loops that if sensor is failing / not present / disconnected will never end.
original code within echoInMicroseconds()
while(digitalRead(_echo) == LOW);
int pulseStart = micros();
while(digitalRead(_echo) == HIGH);
fixed code within echoInMicroseconds()
// sounds go at 350meters/sec, HCSR04 reach is 4mt, to be safe 10mt, at sound speed takes 28 millis
const long timeout=100L; // more than safe in normal conditions.
long started = millis();
boolean timedout = false;
while(digitalRead(_echo) == LOW && !(timedout=(millis()-started > timeout)));
if (timedout) return -1; // negative distance should be treated as error condition.
int pulseStart = micros();
started = millis();
while(digitalRead(_echo) == HIGH && !(timedout=(millis()-started > timeout)));
if (timedout) return -1; // negative distance should be treated as error condition.
That's all.
Regards
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