Daniel Casner
A driver library for Maxbotix / Maxsonar sonar range finders that uses the pulse width output function to achieve better accuracy with less load on the mbed processor.
Dependents: QuadCopter mbed-IBooth-ETH
Diff: sonar.cpp
- Revision:
- 0:7e65f5077f5a
--- /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
+}
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