Honza T. / Distance_HC_SR04

Synchronous and asynchronous library for ultrasonic distance measurement for the device HC-SR04 with error handling functionality (out of range detection, HW error detection). Main features: "echo" puls duration measurement, distance measurement from "echo" pulse duration, detection of "echo" signal malfunction, timeout detection, detection of measured values outside reliable limits (min, max)

Dependents:   TEST_Dist_lib

Distance_HC_SR04.h@6:5beda7c318d5, 2015-12-22 (annotated)

Committer:
dzoni
Date:
Tue Dec 22 12:00:15 2015 +0000
Revision:
6:5beda7c318d5
Parent:
5:2f6992aad3a0
Child:
12:5bf5a7e62c5d
Touch-ups on documentation.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
dzoni 0:4fbf332e6759 1 #ifndef MBED_DISTANCE_HC_SR04_H
dzoni 0:4fbf332e6759 2 #define MBED_DISTANCE_HC_SR04_H
dzoni 0:4fbf332e6759 3
dzoni 0:4fbf332e6759 4 #include "mbed.h"
dzoni 0:4fbf332e6759 5
dzoni 5:2f6992aad3a0 6 #define TIMEOUT_DELAY_US (25000) // Timeout in microseconds
dzoni 5:2f6992aad3a0 7 #define CALC_COEFF (340.0f/(2.0f*1000.0f)) // Coefficient for distance calculation (distance = coeff * microseconds)
dzoni 5:2f6992aad3a0 8 #define TICKS_RANGE_MAX (15000) // Maximum reliable measurement - echo pulse width in microseconds
dzoni 5:2f6992aad3a0 9 #define TICKS_RANGE_MIN (150) // Minimum reliable measurement - echo pulse width in microseconds
dzoni 5:2f6992aad3a0 10 #define TRIG_PULSE_US (50) // Width of trigger pulse in microseconds
dzoni 0:4fbf332e6759 11
dzoni 6:5beda7c318d5 12 /** Definition of measurement FSM states.
dzoni 6:5beda7c318d5 13 *
dzoni 6:5beda7c318d5 14 * IDLE: No activity. Ready to start measurement with trigger(). This is state after reset().
dzoni 6:5beda7c318d5 15 * STARTED: Measurement started and in progress. This is state after trigger().
dzoni 6:5beda7c318d5 16 * COMPLETED: Measurement succesfuly completed by falling edge of echo signal. Measured values in range.
dzoni 6:5beda7c318d5 17 * TIMEOUT: It was not possible to complete echo pulse width measurement in given time. Measurement cancelled.
dzoni 6:5beda7c318d5 18 * OUT_OF_RANGE_MIN: Measurement completed. Measured distance under reliable range.
dzoni 6:5beda7c318d5 19 * OUT_OF_RANGE_MAX: Measurement completed. Measured distance over reliable range.
dzoni 6:5beda7c318d5 20 * ERROR_SIG: Faulty value of echo signal just after trigger pulse (echo != 0). Possible HW fault.
dzoni 6:5beda7c318d5 21 */
dzoni 0:4fbf332e6759 22 typedef enum { IDLE, STARTED, COMPLETED, TIMEOUT, OUT_OF_RANGE_MIN, OUT_OF_RANGE_MAX, ERROR_SIG } Distance_HC_SR04_state;
dzoni 0:4fbf332e6759 23
dzoni 0:4fbf332e6759 24 /** Distance_HC_SR04 class.
dzoni 0:4fbf332e6759 25 *
dzoni 0:4fbf332e6759 26 * Library for interfacing ultrasonic distance measurement device HC-SR04.
dzoni 4:71f01fbc9246 27 * Works in 2 basic modes:
dzoni 6:5beda7c318d5 28 * - blocking (via measureTicks() or measureDistance())
dzoni 6:5beda7c318d5 29 * - non-blocking asynchronous (via reset() + trigger() + getState() + getTicks() or getDistance())
dzoni 4:71f01fbc9246 30 *
dzoni 0:4fbf332e6759 31 * Functionality includes detection of error in echo signal, detection of timeout and limits of reliable measurement.
dzoni 0:4fbf332e6759 32 *
dzoni 0:4fbf332e6759 33 */
dzoni 0:4fbf332e6759 34 class Distance_HC_SR04 {
dzoni 0:4fbf332e6759 35
dzoni 0:4fbf332e6759 36 public:
dzoni 0:4fbf332e6759 37 Distance_HC_SR04(PinName trig, PinName echo, uint32_t tout_us = TIMEOUT_DELAY_US, float coeff = CALC_COEFF,
dzoni 0:4fbf332e6759 38 uint32_t tmin_us = TICKS_RANGE_MIN, uint32_t tmax_us = TICKS_RANGE_MAX);
dzoni 0:4fbf332e6759 39 void trigger(void);
dzoni 0:4fbf332e6759 40 Distance_HC_SR04_state getState(void);
dzoni 0:4fbf332e6759 41 void reset(void);
dzoni 0:4fbf332e6759 42 uint32_t getTicks(void);
dzoni 0:4fbf332e6759 43 float getDistance(void);
dzoni 0:4fbf332e6759 44 float getCoeff(void);
dzoni 0:4fbf332e6759 45 void setCoeff(float coeff);
dzoni 0:4fbf332e6759 46 float measureDistance(void);
dzoni 0:4fbf332e6759 47 uint32_t measureTicks(void);
dzoni 0:4fbf332e6759 48
dzoni 6:5beda7c318d5 49 private:
dzoni 0:4fbf332e6759 50 void _tout(void);
dzoni 0:4fbf332e6759 51 void _rising(void);
dzoni 0:4fbf332e6759 52 void _falling(void);
dzoni 0:4fbf332e6759 53
dzoni 0:4fbf332e6759 54 DigitalOut _trig;
dzoni 0:4fbf332e6759 55 InterruptIn _echo;
dzoni 0:4fbf332e6759 56 uint32_t _tout_us;
dzoni 0:4fbf332e6759 57 float _coeff;
dzoni 0:4fbf332e6759 58 uint32_t _tmin_us;
dzoni 0:4fbf332e6759 59 uint32_t _tmax_us;
dzoni 0:4fbf332e6759 60
dzoni 0:4fbf332e6759 61 Timer _timer;
dzoni 0:4fbf332e6759 62 Timeout _timeout;
dzoni 0:4fbf332e6759 63
dzoni 0:4fbf332e6759 64 volatile Distance_HC_SR04_state _state;
dzoni 0:4fbf332e6759 65 uint32_t _ticks_us;
dzoni 0:4fbf332e6759 66 };
dzoni 0:4fbf332e6759 67
dzoni 0:4fbf332e6759 68 #endif