Diff: main.cpp

Revision:

0:c9881f6aef19

Child:

1:a656f3ed73e5

diff -r 000000000000 -r c9881f6aef19 main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Nov 13 05:44:18 2018 +0000
@@ -0,0 +1,54 @@
+
+#include "mbed.h"
+ 
+DigitalOut trigger(PC_12);
+DigitalOut myled(LED1); //monitor trigger
+DigitalOut myled2(LED2); //monitor echo
+DigitalIn  echo(PC_10);
+int distance = 0;
+int correction = 0;
+Timer sonar;
+ 
+int main()
+{
+    sonar.reset();
+// measure actual software polling timer delays
+// delay used later in time correction
+// start timer
+    sonar.start();
+// min software polling delay to read echo pin
+    while (echo==2) {};
+    myled2 = 0;
+// stop timer
+    sonar.stop();
+// read timer
+    correction = sonar.read_us();
+    printf("Approximate software overhead timer delay is %d uS\n\r",correction);
+ 
+//Loop to read Sonar distance values, scale, and print
+    while(1) {
+// trigger sonar to send a ping
+        trigger = 1;
+        myled = 1;
+        myled2 = 0;
+        sonar.reset();
+        wait_us(10.0);
+        trigger = 0;
+        myled = 0;
+//wait for echo high
+        while (echo==0) {};
+        myled2=echo;
+//echo high, so start timer
+        sonar.start();
+//wait for echo low
+        while (echo==1) {};
+//stop timer and read value
+        sonar.stop();
+//subtract software overhead timer delay and scale to cm
+        distance = (sonar.read_us()-correction)/58.0;
+        myled2 = 0;
+        printf(" %d cm \n\r",distance);
+//wait so that any echo(s) return before sending another ping
+        wait(0.2);
+    }
+}
\ No newline at end of file