Diff: hcsr04.h

Revision:

0:c587e0d5adda

Child:

1:c7753ec66a4b

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hcsr04.h	Fri Mar 16 03:36:59 2012 +0000
@@ -0,0 +1,70 @@
+// HCSR04 ultrasonic sensor class using interrupts and allowing multiple instances.
+// You can use the same trigger pin for multiple instances, the echo is recieved and 
+// measurement calculated based on the echo input alone (when the echo signal goes high
+// the timer is started, when the echo signal is low the timer value in microseconds
+// is saved as the length, and the timer is stopped and reset.  Length calculation is done
+// when the length is requested (either inches or centimeters) using the appropriate
+// function. 
+//
+
+#ifndef MBED_HCSR04_H
+#define MBED_HCSR04_H
+
+//required to use mbed functions
+#include "mbed.h"
+
+#define TRIGGER_DELAY       12      // length of trigger signal expected by HCSR04 sensor
+#define INCHES_DIVISOR      148     // 
+#define CM_DIVISOR          58
+
+class hcsr04 {
+
+private:
+    InterruptIn *_echo_int;						// pin to receive echo signal
+	DigitalOut trigger_out;					// pin to send the trigger signal
+	Timer timer;							// timer to track length of pulse
+	// int timestart;							// beginning time of echo pulse
+    float value;				            // to store the last pulse length		
+
+public:
+    bool measuring;                         // true while the echo signal is high (measurement in progress)
+    hcsr04(PinName trigger, PinName echo) : trigger_out(trigger) { // _pass the names to the pin configuration                              					 
+       // _trigger_out = new DigitalOut( trigger );
+        _echo_int = new InterruptIn( echo );
+        _echo_int->rise(this, &hcsr04::timer_start);
+        _echo_int->fall(this, &hcsr04::calc_measurement);
+        measuring = false;
+    }
+
+
+
+void calc_measurement() {
+    value = timer.read_us();
+	//value = timer.read_us() - timestart;
+	timer.stop();
+	timer.reset();
+	measuring = false;
+}
+	
+void timer_start() {
+	this->timer.start();
+	measuring = true;
+}
+	
+void trigger(void) {
+	trigger_out.write(1);                  	// start trigger signal
+    wait_us(TRIGGER_DELAY); 
+    trigger_out.write(0);	                // end trigger signal
+}
+	
+float inches() {
+    return value / INCHES_DIVISOR;
+}
+	
+float cm() {
+	return value /CM_DIVISOR;
+}
+	
+};
+
+#endif
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