HCSR04.cpp

00001 #include "mbed.h"
00002 #include "HCSR04.h"
00003 
00004 HCSR04::HCSR04(PinName echoPin, PinName triggerPin) : echo(echoPin), trigger(triggerPin) {
00005     init();
00006 }
00007 
00008 void HCSR04::init() {
00009     distance = -1;      // initial distance
00010     minDistance = 2;
00011     maxDistance = 400;
00012     newDataReady = timerStarted = false;
00013 }
00014 
00015 void HCSR04::startTimer() {
00016     if (!timerStarted) {
00017         timer.start(); // start the timer
00018         timerStarted = true;
00019         echoTimeout.attach_us(this, &HCSR04::stopTimer, 25000); // in case echo fall does not occur
00020         echo.fall(this, &HCSR04::stopTimer);
00021         echo.rise(NULL);
00022     }
00023 }
00024 
00025 void HCSR04::stopTimer() {
00026     timer.stop(); // stop the timer
00027     if (timerStarted) {
00028         distance = timer.read() * 1e6 / 58;
00029         if (distance < minDistance)
00030             distance = minDistance;
00031         if (distance > maxDistance)
00032             distance = maxDistance;
00033         newDataReady = true;
00034     }
00035     timer.reset();
00036     timerStarted = false;
00037     echoTimeout.detach();
00038     echo.fall(NULL);
00039 }
00040 
00041 void HCSR04::turnOffTrigger() {
00042     trigger = 0; 
00043 }
00044 
00045 void HCSR04::startMeasurement() {
00046     trigger = 1;
00047     triggerTimeout.attach_us(this, &HCSR04::turnOffTrigger, 10);
00048     echo.rise(this, &HCSR04::startTimer);
00049     newDataReady = false;
00050 }
00051 
00052 float HCSR04::getDistance_cm() {
00053     newDataReady = false;
00054     return distance;
00055 }
00056 
00057 float HCSR04::getDistance_mm() {
00058     newDataReady = false;
00059     return distance * 10;
00060 }
00061 
00062 bool HCSR04::isNewDataReady() {
00063     return newDataReady;
00064 }
00065 
00066 void HCSR04::setRanges(float minRange, float maxRange) {
00067     if (minRange < maxRange) {
00068         if (minRange >= 2 && minRange < 400) // bug from revs. 4 and 5 corrected
00069             minDistance = minRange;
00070         if (maxRange <= 400)
00071             maxDistance = maxRange;
00072     }
00073 }
00074 
00075 float HCSR04::getMinRange() {
00076     return minDistance;
00077 }
00078 
00079 float HCSR04::getMaxRange() {
00080     return maxDistance;
00081 }