Diff: main.cpp

Revision:

0:453df8530a88

Child:

1:010d1ef2f3ab

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Jan 31 16:49:22 2017 +0000
@@ -0,0 +1,192 @@
+// Using MF51E103F3950 NTC 10k Thermistor, with a B value of 3950
+#include "mbed.h"
+
+// which analog pin to connect
+#define THERMISTORPIN A0
+// resistance at 25 degrees C
+#define THERMISTORNOMINAL 10000
+// temp. for nominal resistance (almost always 25 C)
+#define TEMPERATURENOMINAL 25
+// how many samples to take and average, more takes longer
+// but is more 'smooth'
+#define NUMSAMPLES 5
+// The beta coefficient of the thermistor (usually 3000-4000)
+#define BCOEFFICIENT 3950
+// the value of the 'other' resistor
+#define SERIESRESISTOR 10000.0f
+
+#define OFFSET_NUM_AVERAGES 20
+
+Serial pc(USBTX, USBRX); // tx, rx
+AnalogIn ain0(A0);
+AnalogIn ain1(A1);
+AnalogIn ain2(A2);
+AnalogIn ain3(A3);
+AnalogIn ain4(A4);
+AnalogIn ain5(A5);
+AnalogIn ain6(PA_5);
+AnalogIn ain7(PA_6); // Note: on the Nucleo F401, this is connected to the LED.
+AnalogIn ain8(PA_7);
+
+float offsets[9] = {0};
+float resistors[9] = {10000.0f, 10000.0f, 10000.0f, 10000.0f, 10000.0f, 10000.0f, 10000.0f, 10000.0f, 10000.0f};
+
+int main()
+{
+    pc.baud(115200);
+
+    pc.printf("\nThermistor test\n");
+    float rawReading[9] = {0};
+    float reading[9] = {0};
+    
+// Find offset values (take average 20 readings for offset):
+    float sum = 0;
+//    for(uint8_t i = 0; i < OFFSET_NUM_AVERAGES; i++) {
+//        sum += ain0.read();
+//    }
+//    offsets[0] = (sum / OFFSET_NUM_AVERAGES);
+//    
+//    sum = 0;
+//    for(uint8_t i = 0; i < OFFSET_NUM_AVERAGES; i++) {
+//        sum += ain1.read();
+//    }
+//    offsets[1] = (sum / OFFSET_NUM_AVERAGES);
+//    
+//    sum = 0;
+//    for(uint8_t i = 0; i < OFFSET_NUM_AVERAGES; i++) {
+//        sum += ain2.read();
+//    }
+//    offsets[2] = (sum / OFFSET_NUM_AVERAGES);
+//    
+//    sum = 0;
+//    for(uint8_t i = 0; i < OFFSET_NUM_AVERAGES; i++) {
+//        sum += ain3.read();
+//    }
+//    offsets[3] = (sum / OFFSET_NUM_AVERAGES);    
+//
+//    sum = 0;
+//    for(uint8_t i = 0; i < OFFSET_NUM_AVERAGES; i++) {
+//        sum += ain4.read();
+//    }
+//    offsets[4] = (sum / OFFSET_NUM_AVERAGES);
+//
+//    sum = 0;
+//    for(uint8_t i = 0; i < OFFSET_NUM_AVERAGES; i++) {
+//        sum += ain5.read();
+//    }
+//    offsets[5] = (sum / OFFSET_NUM_AVERAGES);
+//            
+//    sum = 0;
+//    for(uint8_t i = 0; i < OFFSET_NUM_AVERAGES; i++) {
+//        sum += ain5.read();
+//    }
+//    offsets[5] = (sum / OFFSET_NUM_AVERAGES);
+//
+//    sum = 0;
+//    for(uint8_t i = 0; i < OFFSET_NUM_AVERAGES; i++) {
+//        sum += ain6.read();
+//    }
+//    offsets[6] = (sum / OFFSET_NUM_AVERAGES);
+//
+//    sum = 0;
+//    for(uint8_t i = 0; i < OFFSET_NUM_AVERAGES; i++) {
+//        sum += ain7.read();
+//    }
+//    offsets[7] = (sum / OFFSET_NUM_AVERAGES);
+//    
+//    sum = 0;
+//    for(uint8_t i = 0; i < OFFSET_NUM_AVERAGES; i++) {
+//        sum += ain8.read();
+//    }
+//    offsets[8] = (sum / OFFSET_NUM_AVERAGES);
+
+// Single reading for offset:
+//    offsets[0] = ain0.read();
+//    offsets[1] = ain1.read();
+//    offsets[2] = ain2.read();
+//    offsets[3] = ain3.read();
+//    offsets[4] = ain4.read();
+//    offsets[5] = ain5.read();
+//    offsets[6] = ain6.read();
+//    offsets[7] = ain7.read();
+//    offsets[8] = ain8.read();
+    
+// Find average of offsets and store in offsets array:
+    sum = 0;
+    float average = 0;
+    
+    for(uint8_t i = 0; i < 9; i++) {
+        sum += offsets[i];
+    }
+    
+    average = sum / 9;
+    
+    for(uint8_t i = 0; i < 9; i++) {
+        offsets[i] = offsets[i] - average;
+    }
+
+    while(1) {
+// Take reading and apply offset, then use voltage divider equation:
+//        rawReading[0] = 1 / (ain0.read() - offsets[0]) - 1;
+//        rawReading[1] = 1 / (ain1.read() - offsets[1]) - 1;
+//        rawReading[2] = 1 / (ain2.read() - offsets[2]) - 1;
+//        rawReading[3] = 1 / (ain3.read() - offsets[3]) - 1;
+//        rawReading[4] = 1 / (ain4.read() - offsets[4]) - 1;
+//        rawReading[5] = 1 / (ain5.read() - offsets[5]) - 1;
+//        rawReading[6] = 1 / (ain6.read() - offsets[6]) - 1;
+//        rawReading[7] = 1 / (ain7.read() - offsets[7]) - 1;
+//        rawReading[8] = 1 / (ain8.read() - offsets[8]) - 1;
+        
+        rawReading[0] = 1 / ain0.read() - 1;
+        rawReading[1] = 1 / ain1.read() - 1;
+        rawReading[2] = 1 / ain2.read() - 1;
+        rawReading[3] = 1 / ain3.read() - 1;
+        rawReading[4] = 1 / ain4.read() - 1;
+        rawReading[5] = 1 / ain5.read() - 1;
+        rawReading[6] = 1 / ain6.read() - 1;
+        rawReading[7] = 1 / ain7.read() - 1;
+        rawReading[8] = 1 / ain8.read() - 1;
+        
+        for(uint8_t i = 0; i < 9; i++) {
+            reading[i] = resistors[i] / rawReading[i];
+        }
+                
+//        pc.printf("Thermistor resistance ");
+//        pc.printf("%f\t", reading0);
+
+// Apply Steinhart equation:
+        for(uint8_t i = 0; i < 9; i++) {
+            float steinhart;
+            steinhart = reading[i] / THERMISTORNOMINAL;     // (R/Ro)
+            steinhart = log(steinhart);                  // ln(R/Ro)
+            steinhart /= BCOEFFICIENT;                   // 1/B * ln(R/Ro)
+            steinhart += 1.0 / (TEMPERATURENOMINAL + 273.15); // + (1/To)
+            steinhart = 1.0f / steinhart;                 // Invert
+            steinhart -= 273.15f;                         // convert to C
+            
+//            pc.printf("Temperature %d: %f *C\t", i, steinhart);
+
+// Print commas for plotting (except at end):
+            if(i == 8) {
+                pc.printf("%.4f", steinhart);
+            }
+            else {
+                pc.printf("%.4f,", steinhart);
+            }
+        }
+        
+        pc.printf("\t\t");
+        
+        for(uint8_t i = 0; i < 9; i++) {
+            if(i == 8) {
+                pc.printf("%.4f", reading[i]);
+            }
+            else {
+                pc.printf("%.4f,", reading[i]);
+            }
+        }
+            
+        pc.printf("\n");
+        wait(.1);
+    }
+}