Diff: main.cpp

Revision:

1:856ad39ba47d

Parent:

0:a4da5990eeb8

--- a/main.cpp	Thu Oct 24 05:24:29 2013 +0000
+++ b/main.cpp	Thu Oct 24 06:19:06 2013 +0000
@@ -3,19 +3,29 @@
  
 SerialLCD lcd(P1_13, P1_14);  /* Grove Serial LCD is connected to UART Tx and Rx pins*/
  
-int main() {
-    int a=0;    
+AnalogIn thermistor(P0_11);   /* Thermistor output connected to P0_11 */
+ 
+int main()
+{
     char strBuffer[16];
+    unsigned int a, beta = 3975;
+    float temperature, resistance;
     
     lcd.begin();                 /* initialize Serial LCD communication. */ 
-    lcd.print("mbed with Arch"); /* print text */
-    
-    while (1) {
-         
-        lcd.setCursor(0, 1);         /* set cursor at 0th column and 1st row */
-        sprintf(strBuffer, "%d", a); /* prepare a string buffer to print number */   
-        lcd.print(strBuffer);        /* print the string buffer */
-        wait(0.1);                   /* wait 100ms */ 
-        a++;
+ 
+    while(1) {
+        a = thermistor.read_u16(); /* Read analog value */
+        
+        /* Calculate the resistance of the thermistor from analog votage read. */
+        resistance= (float) 10000.0 * ((65536.0 / a) - 1.0);
+        
+        /* Convert the resistance to temperature using Steinhart's Hart equation */
+        temperature=(1/((log(resistance/5000.0)/beta) + (1.0/298.15)))-273.15; 
+        
+        sprintf(strBuffer, "Tmp %4.2f deg C", temperature); /* prepare a string buffer to print number */   
+        lcd.setCursor(0, 0);  /* set cursor at 0th column and 0st row */
+        lcd.print(strBuffer); /* print the string buffer */
+      
+        wait(0.5);
     }
 }
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