add polynomial/linear ec calculation

include/ec.h

@@ -42,14 +42,24 @@ ECState ecstate=IDLE;
 float ec_adc;
 float ec_adc_adjusted; //adjusted for reference resistor
 float ec_calib_adc;
+float ec; //ec value after adjustment for reference (at current temperature)
+float ec25; //ec value but temperature adjusted for 25 degC
 
+float ec_tempadjust_alpa=0.2; //TODO
 float ec_reference_adc=5889; //adc reference value for the calibration resistor measurement
 
+//x^0*p[0] + ... + x^n*p[n]
+float ec_calibration_polynom[]={691.5992624638029,-1.4015367296761692,0.0008513503472324141,-2.2140576823179093e-07,2.8962580780180067e-11,-1.8577565383307114e-15,4.7162479484903865e-20};
+float ec_calibration_linearize_below_adc=6000; //use linear approximation below this adc value
+float ec_calibration_linear_lowADC=830; //x0
+float ec_calibration_linear_lowEC=0; //y0
+
 bool ec_measurementReady();
 void ec_startMeasurement();
 void ec_setRange(uint8_t range);
 void ec_connectProbe(bool);
 void ec_releaseRelay();
+float ec_getECfromADC(float adc);
 
 void ec_setup() {
   ledcSetup(EC_PWM_CH, EC_FREQUENCY, EC_RESOLUTION);
@@ -85,6 +95,7 @@ void ec_loop(unsigned long loopmillis) {
         if (isValueArrayOK(ec_calib_array,EC_CALIB_ARRAY_SIZE,0)){
           ec_calib_adc=getMean(ec_calib_array,EC_CALIB_ARRAY_SIZE);
           ec_adc_adjusted=mapf(ec_adc,0,ec_calib_adc,0,ec_reference_adc);
+          ec=ec_getECfromADC(ec_adc_adjusted);
         }
 
         ec_flag_measurement_available=true;
@@ -156,5 +167,26 @@ void ec_releaseRelay() {
   ec_last_change_relay=millis();
 }
 
+float ec_getECfromADC(float adc) {
+  uint8_t polynom_order=sizeof(ec_calibration_polynom) / sizeof(ec_calibration_polynom[0]);
+  double _ec=0;
+  if (adc>=ec_calibration_linearize_below_adc) { //adc is in range where polynomial approximation fits well
+    for (uint8_t i=0;i<polynom_order;i++) {
+      _ec+=pow(adc,i)*ec_calibration_polynom[i];
+    }
+  }else{ //low ec region. linear approximation works better here
+    float x1=ec_calibration_linearize_below_adc;
+    float y1=0;
+    for (uint8_t i=0;i<polynom_order;i++) { //get y1 value from curve
+      y1+=pow(x1,i)*ec_calibration_polynom[i];
+    }
+    float x0=ec_calibration_linear_lowADC;
+    float y0=ec_calibration_linear_lowEC;
+
+    _ec=mapf(adc,x0,x1,y0,y1); //linear approximation    
+  }
+  return _ec;
+}
+
 
 #endif

src/main.cpp

@@ -61,7 +61,17 @@ void setup() {
   //Serial.println("Setup finished");
   delay(200);
 
-  Serial.println("time,tempReservoir,EC,ECadjusted,ECcalib");
+  //Test adc to ec function output
+  Serial.println();
+  for (int i=830;i<13300;i+=100) {
+    float _ec=ec_getECfromADC(i);
+    Serial.print(i); Serial.print(","); Serial.print(_ec); Serial.println();
+  }
+  
+
+  delay(100000);
+
+  Serial.println("time,tempReservoir,ECadcCalib,ECadc,ECadcAdjusted,EC,EC25");
 
 }
 
@@ -108,10 +118,13 @@ void loop() {
       Serial.print(getMeanf(tempCmean_reservoir,TEMPMEAN_SIZE)); Serial.print(",");
       //Serial.print(getMean(sm_mean,SM_SIZE)); Serial.print(",");
       
+      Serial.print(ec_calib_adc); Serial.print(",");
       Serial.print(ec_adc); Serial.print(",");
       Serial.print(ec_adc_adjusted); Serial.print(",");
+      Serial.print(ec); Serial.print(",");
+      Serial.print(ec25);
+      
       
-      Serial.print(ec_calib_adc);
       Serial.println();