changed range conditions
Fork of HCSR04 by
HCSR04.cpp
- Committer:
- srsmitherman
- Date:
- 2013-12-02
- Revision:
- 1:68ad9acbec81
- Parent:
- 0:5461d44a187c
- Child:
- 2:3ebde19131af
File content as of revision 1:68ad9acbec81:
/* 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; triggerTicker.detach(); } // 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(); }