HCSR04.h

00001 #ifndef HCSR04_H_TVZMT
00002 #define HCSR04_H_TVZMT
00003 
00004 /** A distance measurement class using ultrasonic sensor HC-SR04.
00005  *  
00006  * Example of use:
00007  * @code
00008  * #include "mbed.h"
00009  * #include "HCSR04.h"
00010  *
00011  * Serial pc(USBTX, USBRX);
00012  * Timer timer;
00013  *
00014  * int main() {
00015  *     HCSR04 sensor(p5, p7);
00016  *     sensor.setRanges(10, 110);
00017  *     pc.printf("Min. range = %g cm\n\rMax. range = %g cm\n\r",
00018  *       sensor.getMinRange(), sensor.getMaxRange());
00019  *     while(true) {
00020  *         timer.reset();
00021  *         timer.start();
00022  *         sensor.startMeasurement();
00023  *         while(!sensor.isNewDataReady()) {
00024  *             // wait for new data
00025  *             // waiting time depends on the distance
00026  *         }
00027  *         pc.printf("Distance: %5.1f mm\r", sensor.getDistance_mm());
00028  *         timer.stop();
00029  *         wait_ms(500 - timer.read_ms()); // time the loop
00030  *     }
00031  * }
00032  * @endcode
00033  */
00034 class HCSR04 {
00035     
00036     public:
00037     
00038     /** Receives two PinName variables.
00039      * @param echoPin mbed pin to which the echo signal is connected to
00040      * @param triggerPin mbed pin to which the trigger signal is connected to
00041      */
00042     HCSR04(PinName echoPin, PinName triggerPin);
00043     
00044     /** Start the measurement. Measurement time depends on the distance.
00045      *  Maximum measurement time is limited to 25 ms (400 cm).
00046      */
00047     void startMeasurement();
00048     
00049     /** Returns the distance in cm. Requires previous call of startMeasurement().
00050      * @returns distance of the measuring object in cm.
00051      */
00052     float getDistance_cm();
00053     
00054     /** Returns the distance in mm. Requires previous call of startMeasurement().
00055      * @returns distance of the measuring object in mm.
00056      */
00057     float getDistance_mm();
00058     
00059     /** Sets the minimum and maximum ranges between the factory values of 2 cm and 400 cm.
00060      *  @param minRange Minimum range in cm. Must be between 2 cm and maxRange.
00061      *  @param maxRange Maximum range in cm. Must be between minRange and 400 cm.
00062      */
00063     void setRanges(float minRange, float maxRange);
00064     
00065     /** Retreives the minimum sensor range set by the user.
00066      * @returns the minimum sensor range set by the user in cm.
00067      */
00068     float getMinRange();
00069     
00070     /** Retreives the maximum sensor range set by the user.
00071      * @returns the maximum sensor range set by the user in cm.
00072      */
00073     float getMaxRange();
00074     
00075     /** Checks if the new data is ready.
00076      * @returns true if new data is ready, false otherwise.
00077      */
00078     bool isNewDataReady();
00079     
00080     private:
00081     
00082     InterruptIn echo;       // echo pin
00083     DigitalOut trigger;     // trigger pin
00084     Timer timer;            // echo pulsewidth measurement
00085     float distance;         // store the distance in cm
00086     float minDistance;      // minimum measurable distance
00087     float maxDistance;      // maximum measurable distance
00088     Timeout triggerTimeout, echoTimeout;
00089     bool newDataReady, timerStarted;
00090     
00091     /** Start the timer. */
00092     void startTimer();
00093     
00094     /** Stop the timer. */
00095     void stopTimer();
00096     
00097     /** Initialization. */
00098     void init();
00099     
00100     void turnOffTrigger();
00101 };
00102 
00103 #endif