211 lines
6.2 KiB
C
211 lines
6.2 KiB
C
#ifndef _EC_H_
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#define _EC_H_
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#include <Arduino.h>
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bool ec_flag_measurement_available=false;
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#define EC_ADC_UNAVAILABLE 0
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#define EC_UNAVAILABLE -1
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#define EC_PIN_RELAY_PROBE 27
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//#define EC_PIN_ADC 4
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#define EC_ADS_CHANNEL 0
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#define EC_PIN_FREQ 5
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#define EC_PWM_CH 0
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#define EC_RESOLUTION 8
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#define EC_FREQUENCY 5000
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#define EC_CALIB_ARRAY_SIZE 128
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uint16_t ec_calib_array[EC_CALIB_ARRAY_SIZE];
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uint16_t ec_calib_array_pos=0;
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#define EC_CALIB_READ_INTERVAL 250 //interval of reading adc value inside a measurement
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#define EC_ARRAY_SIZE 256
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uint16_t ec_array[EC_ARRAY_SIZE];
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uint16_t ec_array_pos=EC_ARRAY_SIZE;
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unsigned long last_measurement_ec=0;
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#define EC_MEASUREMENT_INTERVAL 30000 //complete filtered measurement every x ms
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//One filtered measurement takes EC_READ_INTERVAL*EC_ARRAY_SIZE*4
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#define EC_READ_INTERVAL 10 //interval of reading adc value inside a measurement. one reading takes about 9-10ms
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#define EC_RELAY_SWITCH_SETTLETIME 500 //time until voltage of ec circuit has settled
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//const uint16_t ec_centerADCvalue=9026; //adc value when probe resistance is equal to the range resistor (mean of both)
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//Range Resistor is two parallel 1k2 = 600 Ohm
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unsigned long ec_last_change_relay=0; //millis of last relay change
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enum ECState{IDLE,MEASURE};
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ECState ecstate=IDLE;
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float ec_adc;
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float ec_adc_adjusted; //adjusted for reference resistor
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float ec_calib_adc;
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float ec; //ec value after adjustment for reference (at current temperature)
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float ec25; //ec value but temperature adjusted for 25 degC
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float ec_tempadjust_alpa=0.02;
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float ec_reference_adc=6016.88; //adc reference value for the calibration resistor measurement.
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//EC short circuit adc value: 17497 (for connection restistance testing)
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//EC open circuit adc value: 738
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//x^0*p[0] + ... + x^n*p[n]
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//float ec_calibration_polynom[]={691.5992624638029,-1.4015367296761692,0.0008513503472324141,-2.2140576823179093e-07,2.8962580780180067e-11,-1.8577565383307114e-15,4.7162479484903865e-20};
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float ec_calibration_polynom[]={1033.928052655456,-3.8909104921922895,0.005627541436014758,-4.103988840997024e-06,1.7231981870816133e-09,-4.433707707721975e-13,7.203892111369395e-17,-7.406549810844244e-21,4.667420606439905e-25,-1.6439457516812463e-29,2.477292190335455e-34};
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float ec_calibration_linearize_below_adc=0; //use linear approximation below this adc value. 0=disable
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float ec_calibration_linear_lowADC=830; //x0
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float ec_calibration_linear_lowEC=0; //y0
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bool ec_measurementReady();
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void ec_startMeasurement();
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void ec_setRange(uint8_t range);
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void ec_connectProbe(bool);
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void ec_releaseRelay();
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float ec_getECfromADC(float adc);
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float ec_calculateEC25(float pEC,float pTemp);
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void ec_setup() {
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ledcSetup(EC_PWM_CH, EC_FREQUENCY, EC_RESOLUTION);
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ledcAttachPin(EC_PIN_FREQ, EC_PWM_CH);
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ledcWrite(EC_PWM_CH, 127); //50% duty cycle
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pinMode(EC_PIN_RELAY_PROBE,OUTPUT); //LOW=Calibration/idle, HIGH=Probe connected
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ec_releaseRelay();
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}
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void ec_loop(unsigned long loopmillis) {
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static unsigned long last_read_ec=0;
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switch (ecstate) {
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case IDLE:
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if (loopmillis>last_measurement_ec+EC_MEASUREMENT_INTERVAL && ecstate==IDLE) { //start measurement if idle
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last_measurement_ec=loopmillis;
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ec_startMeasurement();
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ec_connectProbe(true);
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ecstate=MEASURE;
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}
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break;
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case MEASURE:
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if (ec_measurementReady()) {
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ec_releaseRelay();
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ec_adc=getMean(ec_array,EC_ARRAY_SIZE);
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if (isValueArrayOK(ec_calib_array,EC_CALIB_ARRAY_SIZE,EC_ADC_UNAVAILABLE)){
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ec_calib_adc=getMean(ec_calib_array,EC_CALIB_ARRAY_SIZE);
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ec_adc_adjusted=mapf(ec_adc,0,ec_calib_adc,0,ec_reference_adc);
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ec=ec_getECfromADC(ec_adc_adjusted);
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ec25=ec_calculateEC25(ec,tempC_reservoir);
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}else{
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ec_calib_adc=EC_ADC_UNAVAILABLE;
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ec_adc_adjusted=EC_ADC_UNAVAILABLE;
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ec=EC_UNAVAILABLE;
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ec25=EC_UNAVAILABLE;
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}
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ec_flag_measurement_available=true;
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ecstate=IDLE;
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}
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break;
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}
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if (ec_array_pos<EC_ARRAY_SIZE) { //measurement running
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if (loopmillis>last_read_ec+EC_READ_INTERVAL) { //take reading into array
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last_read_ec=loopmillis;
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if (loopmillis>ec_last_change_relay+EC_RELAY_SWITCH_SETTLETIME) { //values have settled
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uint16_t value = ADS.readADC(EC_ADS_CHANNEL);
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ec_array[ec_array_pos]=value;
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ec_array_pos++;
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}
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}
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}else{ //measurement not running, then take calibration readings
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if (loopmillis>last_read_ec+EC_CALIB_READ_INTERVAL) { //take reading into array
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last_read_ec=loopmillis;
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if (loopmillis>ec_last_change_relay+EC_RELAY_SWITCH_SETTLETIME) { //values have settled
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uint16_t value = ADS.readADC(EC_ADS_CHANNEL);
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ec_calib_array[ec_calib_array_pos]=value;
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ec_calib_array_pos++;
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ec_calib_array_pos%=EC_CALIB_ARRAY_SIZE;
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}
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}
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}
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}
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void ec_startMeasurement() {
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ec_array_pos=0;
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}
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bool ec_measurementReady(){
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if (ec_array_pos>=EC_ARRAY_SIZE) { //reached end of both arrays
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return true;
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}else{
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return false;
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}
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}
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void ec_connectProbe(bool relay) {
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bool val=digitalRead(EC_PIN_RELAY_PROBE);
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if (val!=relay) { //write only if different
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digitalWrite(EC_PIN_RELAY_PROBE,relay);
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ec_last_change_relay=millis();
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}
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}
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void ec_releaseRelay() {
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digitalWrite(EC_PIN_RELAY_PROBE,LOW);
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ec_last_change_relay=millis();
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}
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float ec_getECfromADC(float adc) {
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uint8_t polynom_order=sizeof(ec_calibration_polynom) / sizeof(ec_calibration_polynom[0]);
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double _ec=0;
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if (adc>=ec_calibration_linearize_below_adc) { //adc is in range where polynomial approximation fits well
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for (uint8_t i=0;i<polynom_order;i++) {
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_ec+=pow(adc,i)*ec_calibration_polynom[i];
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}
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}else{ //low ec region. linear approximation works better here
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float x1=ec_calibration_linearize_below_adc;
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float y1=0;
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for (uint8_t i=0;i<polynom_order;i++) { //get y1 value from curve
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y1+=pow(x1,i)*ec_calibration_polynom[i];
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}
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float x0=ec_calibration_linear_lowADC;
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float y0=ec_calibration_linear_lowEC;
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_ec=mapf(adc,x0,x1,y0,y1); //linear approximation
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}
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return _ec;
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}
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float ec_calculateEC25(float pEC,float pTemp)
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{
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return pEC/(1.0+ec_tempadjust_alpa*(pTemp-25.0));
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}
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#endif |