mbed device driver for HC-SR04 ultrasonic range finder
Dependents: ROBot Ultrasonic Ksen Core1000_SmartFarm ... more
Revision 0:5461d44a187c, committed 2013-11-24
- Comitter:
- rabad1
- Date:
- Sun Nov 24 21:45:46 2013 +0000
- Commit message:
- initial release
Changed in this revision
HCSR04.cpp | Show annotated file Show diff for this revision Revisions of this file |
HCSR04.h | Show annotated file Show diff for this revision Revisions of this file |
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/HCSR04.cpp Sun Nov 24 21:45:46 2013 +0000 @@ -0,0 +1,100 @@ +/* File: HCSR04.h + * Author: Robert Abad Copyright (c) 2013 + * + * Desc: driver for HCSR04 Ultrasonic Range Finder. See header file, + * HCSR04.h, for more details. + */ + +#include "mbed.h" +#include "HCSR04.h" + +#define SPEED_OF_SOUND (343.2f) // meters/sec + +// HCSR04 TRIGGER pin +#define SIGNAL_HIGH (1) +#define SIGNAL_LOW (0) + +#define TRIGGER_TIME (10) // microseconds + + +// Name: HCSR04 +// Desc: HCSR04 constructor +// Inputs: PinName - pin used for trigger signal +// PinName - pin used for echo signal +// Outputs: none +// +HCSR04::HCSR04( PinName pinTrigger, PinName pinEcho ) : +trigger(pinTrigger), +echo(pinEcho), +measTimeStart_us(0), +measTimeStop_us(0) +{ + echo.rise( this, &HCSR04::ISR_echoRising ); + echo.fall( this, &HCSR04::ISR_echoFalling ); + echoTimer.start(); +} + +// Name: startMeas +// Desc: initiates range measurement driving the trigger signal HIGH then sets +// a timer to keep trigger HIGH for the duration of TRIGGER_TIME +// Inputs: none +// Outputs: none +// +void HCSR04::startMeas(void) +{ + trigger = SIGNAL_HIGH; + echoTimer.reset(); + triggerTicker.attach_us(this, &HCSR04::triggerTicker_cb, TRIGGER_TIME); +} + +// Name: getMeas +// Desc: returns range measurement in meters +// Inputs: float & - reference to range measurement +// Outputs: etHCSR04 - RANGE_MEAS_VALID or RANGE_MEAS_INVALID +// +etHCSR04_RANGE_STATUS HCSR04::getMeas(float &rRangeMeters) +{ + unsigned long dTime_us; + if ( !measTimeStart_us || !measTimeStop_us ) + { + return RANGE_MEAS_INVALID; + } + + dTime_us = measTimeStop_us - measTimeStart_us; + rRangeMeters = (float)dTime_us / 1000000. * SPEED_OF_SOUND / 2; + measTimeStart_us = 0; + measTimeStop_us = 0; + return ( RANGE_MEAS_VALID ); +} + +// Name: triggerTicker_cb +// Desc: Timer ticker callback function used to drive trigger signal LOW +// Inputs: none +// Outputs: none +// +void HCSR04::triggerTicker_cb(void) +{ + trigger = SIGNAL_LOW; +} + + +// Name: ISR_echoRising +// Desc: ISR for rising edge of HCSR04 ECHO signal +// Inputs: none +// Outputs: none +// +void HCSR04::ISR_echoRising(void) +{ + measTimeStart_us = echoTimer.read_us(); +} + +// Name: ISR_echoFalling +// Desc: ISR for falling edge of HCSR04 ECHO signal +// Inputs: none +// Outputs: none +// +void HCSR04::ISR_echoFalling(void) +{ + measTimeStop_us = echoTimer.read_us(); +} +
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/HCSR04.h Sun Nov 24 21:45:46 2013 +0000 @@ -0,0 +1,72 @@ +/* File: HCSR04.h + * Author: Robert Abad Copyright (c) 2013 + * + * Desc: driver for HCSR04 Ultrasonic Range Finder. The returned range + * is in units of meters. + * + * To use this driver you must call the methods ::startMeas() + * and ::getMeas(). The HCSR04 requires a trigger time of + * 10 usec (microseconds) which is initiated by ::startMeas(). + * If a successful measurement is made, getMeas() will return + * RANGE_MEAS_VALID. If unsuccessful, initiate a new measurement. + * + * The datasheet for this device can be found here: + * http://www.elecfreaks.com/store/download/product/Sensor/HC-SR04/HC-SR04_Ultrasonic_Module_User_Guide.pdf + * + * Below is some sample code: + * + * #include "mbed.h" + * #include "HCSR04.h" + * + * #define PIN_TRIGGER (p14) + * #define PIN_ECHO (p15) + * + * int main(void) + * { + * HCSR04 rangeFinder( PIN_TRIGGER, PIN_ECHO ); + * float range; + * + * while (1) + * { + * rangeFinder.startMeas(); + * wait(0.1); + * if ( rangeFinder.getMeas(range) == RANGE_MEAS_VALID ) + * { + * printf("range = %f\n\r", range); + * } + * } + * } + */ + +#ifndef __HCSR04_H__ +#define __HCSR04_H__ + +#include "mbed.h" + +typedef enum +{ + RANGE_MEAS_INVALID, + RANGE_MEAS_VALID +} etHCSR04_RANGE_STATUS; + +class HCSR04 +{ +public: + HCSR04( PinName pinTrigger, PinName pinEcho ); + void startMeas(void); + etHCSR04_RANGE_STATUS getMeas(float &rRangeMeters); + +private: + DigitalOut trigger; + Ticker triggerTicker; + InterruptIn echo; + Timer echoTimer; + unsigned long measTimeStart_us; + unsigned long measTimeStop_us; + + void triggerTicker_cb(void); // trigger ticker callback function + void ISR_echoRising(void); // ISR for rising edge + void ISR_echoFalling(void); // ISR for falling edge +}; + +#endif /* __HCSR04_H__ */