A distance measurement class using ultrasonic sensor HC-SR04.
Dependents: Esercitazione4_4 HC-SR04 Group10_slave Oled_Gus ... more
The purpose of this library is to encourage students to develope their own classes. Instructions how to follow the development of this library for ultrasonic distance measurement are given here.
Diff: HCSR04.cpp
- Revision:
- 6:cf3e4e307d15
- Parent:
- 4:aae70f15357f
diff -r a667b621f625 -r cf3e4e307d15 HCSR04.cpp --- a/HCSR04.cpp Mon Dec 07 09:57:48 2015 +0000 +++ b/HCSR04.cpp Sat Dec 10 08:26:18 2016 +0000 @@ -6,52 +6,66 @@ } void HCSR04::init() { - /** configure the rising edge to start the timer */ - echo.rise(this, &HCSR04::startTimer); - - /** configure the falling edge to stop the timer */ - echo.fall(this, &HCSR04::stopTimer); - distance = -1; // initial distance minDistance = 2; maxDistance = 400; + newDataReady = timerStarted = false; } void HCSR04::startTimer() { - timer.start(); // start the timer + if (!timerStarted) { + timer.start(); // start the timer + timerStarted = true; + echoTimeout.attach_us(this, &HCSR04::stopTimer, 25000); // in case echo fall does not occur + echo.fall(this, &HCSR04::stopTimer); + echo.rise(NULL); + } } void HCSR04::stopTimer() { timer.stop(); // stop the timer + if (timerStarted) { + distance = timer.read() * 1e6 / 58; + if (distance < minDistance) + distance = minDistance; + if (distance > maxDistance) + distance = maxDistance; + newDataReady = true; + } + timer.reset(); + timerStarted = false; + echoTimeout.detach(); + echo.fall(NULL); +} + +void HCSR04::turnOffTrigger() { + trigger = 0; } void HCSR04::startMeasurement() { trigger = 1; - wait_us(10); - trigger = 0; - wait_us(23660); // just enough time to measure 400 cm - timer.stop(); // just in case echo fall did not occur - distance = timer.read() * 1e6 / 58; - if (distance < minDistance) - distance = minDistance; - if (distance > maxDistance) - distance = maxDistance; - timer.reset(); + triggerTimeout.attach_us(this, &HCSR04::turnOffTrigger, 10); + echo.rise(this, &HCSR04::startTimer); + newDataReady = false; } float HCSR04::getDistance_cm() { - startMeasurement(); + newDataReady = false; return distance; } float HCSR04::getDistance_mm() { - startMeasurement(); + newDataReady = false; return distance * 10; } +bool HCSR04::isNewDataReady() { + return newDataReady; +} + void HCSR04::setRanges(float minRange, float maxRange) { if (minRange < maxRange) { - if (minRange >= 2) + if (minRange >= 2 && minRange < 400) // bug from revs. 4 and 5 corrected minDistance = minRange; if (maxRange <= 400) maxDistance = maxRange;