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  *
00013  * int main() {
00014  *     HCSR04 sensor(p5, p7);
00015  *     sensor.setRanges(10, 110);
00016  *     pc.printf("Min. range = %g cm\n\rMax. range = %g cm\n\r",
00017  *       sensor.getMinRange(), sensor.getMaxRange());
00018  *     while(1) {
00019  *         pc.printf("Distance: %5.1f mm\r", sensor.getDistance_mm());
00020  *         wait_ms(500);
00021  *     }
00022  * }
00023  * @endcode
00024  */
00025 class HCSR04 {
00026     
00027     public:
00028     
00029     /** Receives two PinName variables.
00030      * @param echoPin mbed pin to which the echo signal is connected to
00031      * @param triggerPin mbed pin to which the trigger signal is connected to
00032      */
00033     HCSR04(PinName echoPin, PinName triggerPin);
00034     
00035     /** Calculates the distance in cm, with the calculation time of approximatelly 23.7 ms.
00036      * @returns distance of the measuring object in cm.
00037      */
00038     float getDistance_cm();
00039     
00040     /** Calculates the distance in mm, with the calculation time of approximatelly 23.7 ms.
00041      * @returns distance of the measuring object in mm.
00042      */
00043     float getDistance_mm();
00044     
00045     /** Sets the minimum and maximum ranges between the factory values of 2 cm and 400 cm.
00046      *  @param minRange Minimum range in cm. Must be between 2 cm and maxRange.
00047      *  @param maxRange Maximum range in cm. Must be between minRange and 400 cm.
00048      */
00049     void setRanges(float minRange, float maxRange);
00050     
00051     /** Retreives the minimum sensor range set by the user.
00052      * @returns the minimum sensor range set by the user in cm.
00053      */
00054     float getMinRange();
00055     
00056     /** Retreives the maximum sensor range set by the user.
00057      * @returns the maximum sensor range set by the user in cm.
00058      */
00059     float getMaxRange();
00060     
00061     private:
00062     
00063     InterruptIn echo;       // echo pin
00064     DigitalOut trigger;     // trigger pin
00065     Timer timer;            // echo pulsewidth measurement
00066     float distance;         // store the distance in cm
00067     float minDistance;      // minimum measurable distance
00068     float maxDistance;      // maximum measurable distance
00069     
00070     /** Start the timer. */
00071     void startTimer();
00072     
00073     /** Stop the timer. */
00074     void stopTimer();
00075     
00076     /** Initialization. */
00077     void init();
00078     
00079     /** Start the measurement. */
00080     void startMeasurement();
00081 };
00082  
00083 #endif