Diff: main.cpp

Revision:

1:bdb889fd3bef

Parent:

0:dba2bcefd284

Child:

2:5628e75c533e

--- a/main.cpp	Wed Aug 24 23:11:45 2011 +0000
+++ b/main.cpp	Thu Aug 25 12:46:50 2011 +0000
@@ -1,3 +1,8 @@
+/*
+ * humidity1
+ *
+ */
+
 #include "mbed.h"
 
 DigitalOut myled(LED1);
@@ -5,30 +10,46 @@
 AnalogIn hum(p20);
 AnalogIn ref(p19);
 
-float av[5] = {0,0,0,0,0};
+int main() {
+    float av0 = 0.0;
+    float alpha = 0.5;
 
-int main() {
+    printf("humidity1\n\r");
+
     while(1) {
     
-        float h = hum.read();
-        float r = ref.read();
-        float v = 5.0*h/r;
+        // read many times to remove noise
+        int n = 1000;
+        float h = 0.0;
+        float r = 0.0;
+        float v = 0.0;
+        for(int i=0; i<n; ++i) {
+            float h1, r1;
+            h1 = hum.read();
+            r1 = ref.read();
+            h += h1;
+            r += r1;
+            v += 5.0*h1/r1; // convert to 5v reference
+        }
+        h /= n;
+        r /= n;
+        v /= n;
         
-        av[0] = av[1];
-        av[1] = av[2];
-        av[2] = av[3];
-        av[3] = av[4];
-        av[4] = v;
+        // EMA
+        float av = av0 + alpha*(v-av0);
+        av0 = av;
         
-        float a = (av[0]+av[1]+av[2]+av[3]+av[4])/5.0;
-        
-        float m = (a-0.8)/3.0*100.0;
+        // scale to humidity%
+        float m = (av-0.8)/3.0*100.0;
                 
-        printf("h=%1.2f r=%1.2f %1.2f %1.2f %3.1f\n\r", h, r, v, a, m );
+        printf("h=%1.4f r=%1.4f %1.4fv %1.4fv %3.1f%%\n\r", h, r, v, av, m );
     
         myled = 1;
         wait(0.2);
         myled = 0;
         wait(0.8);
-    }
-}
+        
+    } // while
+    
+} // main
+