Revision 0:812fda2beeaa, committed 2013-06-23

Comitter:

simonbarker

Date:

Sun Jun 23 10:21:15 2013 +0000

Commit message:

Commented RPM meter using QTR-1A Reflectance Sensor sensor

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Jun 23 10:21:15 2013 +0000
@@ -0,0 +1,47 @@
+#include "mbed.h"
+
+AnalogIn input(p20);
+DigitalOut led1(LED1);
+Serial pc(USBTX, USBRX); // tx, rx
+Timer t;
+
+int main() {
+    float sample;
+    bool newDetection = true;   //need this as multiple reads happen across white spot
+    int samples[120];           //higher number = greater accuracy but longer read time
+    int sampleCount = 0;
+        
+    pc.printf("Starting:\n\r"); 
+
+    //start initial timer
+    t.start();
+
+    while(1) {
+        //poll analogue in
+        sample = input.read();
+        if(sample < 0.1 && newDetection == true){       //tune 0.1 to appropriate level
+            //detected white spot so stop timer
+            samples[sampleCount] = t.read_us();
+            t.reset();
+            //reset flag
+            newDetection = false;
+            sampleCount++;
+            
+            //change for shorter/longer read times - must be less than array length (set in ling 11)
+            if(sampleCount == 100){
+                //total up time and average across number of readings taken
+                int total = 0;
+                for(int i = 1; i < 99; i++){    //start at 1 as the first one will be a junk reading
+                    total += samples[i];
+                }
+                float ave = total/98;
+                float rpm = (1000000/ave)*60;   //convert from us to rpm
+                pc.printf("RPM = %f\r\n",rpm);
+                sampleCount = 0;
+            }
+        }
+        else if(sample > 0.9){      //tune 0.9 to appropriate level
+            newDetection = true;
+        }
+    }
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Sun Jun 23 10:21:15 2013 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/5e5da4a5990b
\ No newline at end of file