Diff: thermister_ert-j0eg1.cpp

Revision:

5:88bf5a42812e

Parent:

1:cc492e6ba333

Child:

6:3c9cb2bd08c6

--- a/thermister_ert-j0eg1.cpp	Thu Mar 10 22:15:04 2016 +0000
+++ b/thermister_ert-j0eg1.cpp	Wed Mar 30 13:32:40 2016 +0000
@@ -1,19 +1,45 @@
 #include "mbed.h"
 #include "ohms.h"  // from library ohms_law
-
+#include "thermister_ert-j0eg1.h"
 // Set of resistance values from data sheet used to lookup temperature to find
 // location in a 5V band. 
-static long thermisterResistance[] = {205200,154800,117900,90690,70370,50570,43440,34530,27640,22270,18060,14740,12110,
+const  long thermisterResistance[] = {205200,154800,117900,90690,70370,50570,43440,34530,27640,22270,18060,14740,12110,
                   10000,8309,6941,5828,4916,4165,3542,3027,2595,2233,1929,1672,1451,1261,1097,956,836,732,642,565,499};                  
-static int thermisterBase = -40;
-static int thermisterStep = 5;
-static int thermisterMaxTemp = 125;
-const float adc_ref = 3.30;
-
-
+const  int thermisterBase = -40.0f;
+const  int thermisterStep = 5.0f;
+const  int thermisterMaxTemp = 125.0f;
 
 float conv_c_to_f(float tempC) {  
-  return (tempC * 1.8) + 32.0;
+  return (tempC * 1.8f) + 32.0f;
+}
+
+float conv_f_to_c(float tempF) {
+    return (tempF - 32.0f) * 0.55555555555f;
+}
+
+float ERTThermisterRead(PinName apin) {
+  #ifdef DEBUG3
+    printf("ERTThermisterRead start\r\n");
+  #endif
+  AnalogIn adcPin(apin);
+  float tmp = ERTThermisterReadTemp(adcPin);
+  #ifdef DEBUG3
+    printf("ERTThermisterRead temp=%f done\r\n", tmp);
+  #endif
+  return tmp;
+}
+
+// read the temp from thermister and print out
+// both the reading and intermediate values.
+float ERTThermisterReadPrint(Serial log, char *label, PinName apin) {
+   AnalogIn adcpin(apin);
+   float sensorValue = adcpin.read() * ERTThermisterAdcRef;
+   long sensorResist = calcResistV(22000, ERTThermisterAdcRef, sensorValue);
+   float t1C = ERTThermisterReadTemp(adcpin);
+   float t1F = conv_c_to_f(t1C);                
+   log.printf("%s\tvin=%4.2f\tresist=%ld\tT1C=%4.1f\tT1F=%4.2f\r\n", 
+      label, sensorValue, sensorResist, t1C, t1F);
+   return t1C;        
 }
 
 
@@ -22,40 +48,54 @@
  lower than our specified value which gives us temp with 5C spread
  then adjust by how far our sensor reading is above the lower
  bound of the range.*/
-float readTemp(AnalogIn adcpin) {    
+float ERTThermisterReadTemp(AnalogIn adcpin) {    
     //sensorValue = avgRead(adcpin,3,2);
-    float sensorValue = adcpin.read() * adc_ref;    
-    long sensorResist =  calcResistV(22000, adc_ref, sensorValue);
+    float sensorValue = adcpin.read() * ERTThermisterAdcRef;    
+    long sensorResist =  calcResistV(22000, ERTThermisterAdcRef, sensorValue);
     int tempCnt = thermisterBase;   
     int tempndx = 0;
-    
-    if  (sensorValue >= thermisterResistance[0]) {
-      return -255;
+    #ifdef DEBUG3
+       printf("start ERTThermisterReadTemp adc=%4.2f resist=%ld\r\n", sensorValue, sensorResist);
+    #endif
+    if  (sensorResist >= thermisterResistance[0]) {
+      #ifdef DEBUG3
+        printf("resist too high\r\n");
+      #endif
+      return ERTThermisterErrorUnder;
     }
     
+    #ifdef DEBUG3
+      printf("entering while loop sensorResist=%ld thermisterResistance[0]=%ld\r\n",sensorResist, thermisterResistance[0]);
+    #endif
     while (sensorResist < thermisterResistance[tempndx]) {     
        tempndx++;
        tempCnt += thermisterStep;
        if (tempCnt >= thermisterMaxTemp) {
-         return 255;
+         return ERTThermisterErrorOver;
        }
     }
-    tempCnt -= thermisterStep; // backup to begin of range    
+    tempCnt -= thermisterStep; // backup to begin of range 
+    #ifdef DEBUG3   
+    printf("tempCnt=%d\r\n", tempCnt);
+    #endif
     int lowTempResist = thermisterResistance[tempndx -1];
     int highTempResist = thermisterResistance[tempndx];
     int resistRangeDelta = lowTempResist - highTempResist;
     float degreesPerUnit = (float) thermisterStep / (float) (resistRangeDelta);
     int unitOverlow = lowTempResist - sensorResist;
     float degreeAdj = (float) unitOverlow * degreesPerUnit;
+    #ifdef DEBUG3
+    printf("degreeAdj=%f\r\n", degreeAdj);
+    #endif
     return (float) tempCnt + degreeAdj;
 }
 
-float avgReadTemp(AnalogIn adcpin, int numRead) {
+float ERTThermisterAvgReadTemp(AnalogIn adcpin, int numRead) {
   float sum = 0;
   int ndx; 
   for (ndx = 0; ndx < numRead; ndx++) {
     wait(0.005);
-    sum += readTemp(adcpin);
+    sum += ERTThermisterReadTemp(adcpin);
   }
   return (float) ((float) sum / (float) ndx);
 }