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

Diff: Distance_HC_SR04.h

Revision:
6:5beda7c318d5
Parent:
5:2f6992aad3a0
Child:
12:5bf5a7e62c5d
--- a/Distance_HC_SR04.h	Tue Dec 22 11:22:56 2015 +0000
+++ b/Distance_HC_SR04.h	Tue Dec 22 12:00:15 2015 +0000
@@ -9,14 +9,24 @@
 #define TICKS_RANGE_MIN     (150)                       // Minimum reliable measurement - echo pulse width in microseconds
 #define TRIG_PULSE_US       (50)                        // Width of trigger pulse in microseconds
 
+/** Definition of measurement FSM states.
+ *
+ *  IDLE:       No activity. Ready to start measurement with trigger(). This is state after reset().
+ *  STARTED:    Measurement started and in progress. This is state after trigger().
+ *  COMPLETED:  Measurement succesfuly completed by falling edge of echo signal. Measured values in range.
+ *  TIMEOUT:    It was not possible to complete echo pulse width measurement in given time. Measurement cancelled.
+ *  OUT_OF_RANGE_MIN: Measurement completed. Measured distance under reliable range.
+ *  OUT_OF_RANGE_MAX: Measurement completed. Measured distance over reliable range.
+ *  ERROR_SIG:        Faulty value of echo signal just after trigger pulse (echo != 0). Possible HW fault.
+ */
 typedef enum { IDLE, STARTED, COMPLETED, TIMEOUT, OUT_OF_RANGE_MIN, OUT_OF_RANGE_MAX, ERROR_SIG } Distance_HC_SR04_state;
 
 /** Distance_HC_SR04 class.
  *
  *  Library for interfacing ultrasonic distance measurement device HC-SR04.
  *  Works in 2 basic modes:
- *    - blocking (via reset() + trigger() + getState() + getTicks() or detDistance()
- *    - non-blocking (asynchronous) via measureTicks() or measureDistance()
+ *    - blocking (via measureTicks() or measureDistance())
+ *    - non-blocking asynchronous (via reset() + trigger() + getState() + getTicks() or getDistance())
  *
  *  Functionality includes detection of error in echo signal, detection of timeout and limits of reliable measurement.
  *
@@ -36,11 +46,11 @@
     float measureDistance(void);
     uint32_t measureTicks(void);
 
+private:
     void _tout(void);
     void _rising(void);
     void _falling(void);
 
-private:
     DigitalOut  _trig;
     InterruptIn _echo;
     uint32_t    _tout_us;