move calibration values to defines

newcode/main.c

@@ -8,10 +8,15 @@
 
 #define AVRG 512
 
+#define SUPPLY_VOLTS 3.3
+#define REF_OHMS 993.5
+
+#define ADC_0V_COUNT 170
+#define ADC_MAX_VOLT 1.95
+
 volatile uint16_t adc_buffer[AVRG];
 volatile float ch_values[9];
 
-
 void init_clk(void)
 {
     // ========= System Clock configuration =========
@@ -160,10 +165,10 @@ ISR(DMA_CH0_vect){
     ADCA.CH0.MUXCTRL = pin << ADC_CH_MUXPOS_gp; // give MUX time to switch during averaging
     float temp = avrg(adc_buffer, AVRG);
 
-    temp = temp - 170;
-    temp = (temp)/ 3926 * 1.95;
-    temp = (temp*993.5)/(3.3-temp);
-    temp = (temp-100)/0.3927;
+    temp = temp - ADC_0V_COUNT;
+    temp = (temp)/ (4096-ADC_0V_COUNT) * ADC_MAX_VOLT;
+    temp = (temp * REF_OHMS)/(SUPPLY_VOLTS - temp);
+    temp = (temp-100)/0.3927; //pt100 formula
     ch_values[old_pin] = temp;
 
     DMA.CH0.TRIGSRC = DMA_CH_TRIGSRC_ADCA_CH0_gc;