Revision 0:7e65f5077f5a, committed 2012-11-21

Comitter:

DanielC

Date:

Wed Nov 21 20:47:05 2012 +0000

Commit message:

Initial commit of probably working but untested sonar driver library.

Changed in this revision

diff -r 000000000000 -r 7e65f5077f5a sonar.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sonar.cpp	Wed Nov 21 20:47:05 2012 +0000
@@ -0,0 +1,28 @@
+#include "sonar.h"
+
+Sonar::Sonar(PinName input, Timer& t) :
+    interrupt(input),
+    time(t),
+    pulseStartTime(0),
+    range(0) {
+    interrupt.rise(this, &Sonar::pulseStart);
+    interrupt.fall(this, &Sonar::pulseStop);
+}
+
+int Sonar::read() {
+    return range;
+}
+
+Sonar::operator int() {
+    return read();
+}
+
+void Sonar::pulseStart() {
+    pulseStartTime = time.read_us();
+}
+
+void Sonar::pulseStop() {
+    int endTime = time.read_us();
+    if (endTime < pulseStartTime) return; // Escape if there's been a roll over
+    range = (endTime - pulseStartTime) / 58; // 58uS per CM
+}
\ No newline at end of file

diff -r 000000000000 -r 7e65f5077f5a sonar.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sonar.h	Wed Nov 21 20:47:05 2012 +0000
@@ -0,0 +1,42 @@
+#include "mbed.h"
+/*** @file Driver for Maxbotix sonar modules
+ * Uses pulse width input to read range results.
+ * @author Daniel Casner <http://www.danielcasner.org>
+ *
+ * Known Issues:
+ * If a timer rollover occures during a sample, the driver will drop that sample.
+ */
+ 
+ /** Object representation of a sonar instance
+  */
+ class Sonar {
+ public:
+    /** Sets up the driver and starts taking measurements
+     * @param input The pin to read pulses from
+     * @param t A running timer instance used to measure pulse width.
+     * Note that the timer must have been started or results will be
+     * invalid.
+     */
+    Sonar(PinName input, Timer& t);
+    
+    /// Returns range in cm as int
+    int read();
+    
+    /// Returns the range in CM as an int
+    operator int();
+    
+ private:
+    /// Inturrupt at start of pulse
+    void pulseStart();
+    /// Interrupt at end of pulse
+    void pulseStop();
+    
+    /// Interrupt driver for the input pin
+    InterruptIn interrupt;
+    /// Reference to global timer instance
+    Timer& time;
+    /// Time of the start of the current pulse
+    int pulseStartTime;
+    /// The most recent sample
+    int range;
+ };
\ No newline at end of file