blynk-opentherm-thermostat.ino

/*************************************************************
  This example runs directly on ESP8266 chip.

  Please be sure to select the right ESP8266 module
  in the Tools -> Board -> WeMos D1 Mini

  Change WiFi ssid, pass, and Blynk auth token to run  
 *************************************************************/

/* Comment this out to disable prints and save space */
#define BLYNK_PRINT Serial

#include <ESP8266WiFi.h>
#include <BlynkSimpleEsp8266.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#include <OpenTherm.h>

// You should get Auth Token in the Blynk App.
// Go to the Project Settings (nut icon).
char auth[] = "XXX-AUTH-TOKEN-XXX";

// Use Virtual pin 0 for current room temperature display
#define ROOM_TEMP_PIN V0
// Use Virtual pin 1 for setpoint manage & display
#define SETPOINT_PIN V1

// Your WiFi credentials.
// Set password to "" for open networks.
char ssid[] = "WIFI-SSID";
char pass[] = "WIFI-PASSWORD";

//Master OpenTherm Shield pins configuration
const int OT_IN_PIN = 4;  //4 for ESP8266 (D2), 21 for ESP32
const int OT_OUT_PIN = 5; //5 for ESP8266 (D1), 22 for ESP32

//Temperature sensor pin
const int ROOM_TEMP_SENSOR_PIN = 14; //for Arduino, 14 for ESP8266 (D5), 18 for ESP32

float sp = 20, //set point
t = 0, //current temperature
t_last = 0, //prior temperature
ierr = 0, //integral error
dt = 0, //time between measurements
op = 0; //PID controller output
unsigned long ts = 0, new_ts = 0; //timestamp

OneWire oneWire(ROOM_TEMP_SENSOR_PIN);
DallasTemperature sensors(&oneWire);
OpenTherm ot(OT_IN_PIN, OT_OUT_PIN);
BlynkTimer timer;

void ICACHE_RAM_ATTR handleInterrupt() {
    ot.handleInterrupt();
}

float getTemp() {
  return sensors.getTempCByIndex(0);
}

float pid(float sp, float pv, float pv_last, float& ierr, float dt) {    
  float KP = 10;
  float KI = 0.02;  
  // upper and lower bounds on heater level
  float ophi = 80;
  float oplo = 10;
  // calculate the error
  float error = sp - pv;
  // calculate the integral error
  ierr = ierr + KI * error * dt;  
  // calculate the measurement derivative
  float dpv = (pv - pv_last) / dt;
  // calculate the PID output
  float P = KP * error; //proportional contribution
  float I = ierr; //integral contribution  
  float op = P + I;
  // implement anti-reset windup
  if ((op < oplo) || (op > ophi)) {
    I = I - KI * error * dt;
    // clip output
    op = max(oplo, min(ophi, op));
  }
  ierr = I; 
  Serial.println("sp="+String(sp) + " pv=" + String(pv) + " dt=" + String(dt) + " op=" + String(op) + " P=" + String(P) + " I=" + String(I));
  return op;
}


// This function calculates temperature and sends data to Blynk app every second.
// In the app, Widget's reading frequency should be set to PUSH. This means
// that you define how often to send data to Blynk App.
void updateData()
{ 
  //Set/Get Boiler Status
  bool enableCentralHeating = true;
  bool enableHotWater = true;
  bool enableCooling = false;
  unsigned long response = ot.setBoilerStatus(enableCentralHeating, enableHotWater, enableCooling);
  OpenThermResponseStatus responseStatus = ot.getLastResponseStatus();
  if (responseStatus != OpenThermResponseStatus::SUCCESS) {
    Serial.println("Error: Invalid boiler response " + String(response, HEX));
  }   
  
  t = sensors.getTempCByIndex(0);
  new_ts = millis();
  dt = (new_ts - ts) / 1000.0;
  ts = new_ts;
  if (responseStatus == OpenThermResponseStatus::SUCCESS) {
    op = pid(sp, t, t_last, ierr, dt);
    //Set Boiler Temperature    
    ot.setBoilerTemperature(op);
  }
  t_last = t;
  sensors.requestTemperatures(); //async temperature request
  
  Blynk.virtualWrite(ROOM_TEMP_PIN, t);
  Blynk.virtualWrite(SETPOINT_PIN, sp);
  Serial.println("Current temperature is " + String(t) + " degrees C");
}


// This function will be called every time Slider Widget
// in Blynk app writes values to the Virtual Pin 1
BLYNK_WRITE(SETPOINT_PIN)
{
  sp = param.asFloat(); // assigning incoming value from pin V1 to a variable  
  Serial.print("V1 Slider value is: ");
  Serial.println(sp);  
}

// This function tells Arduino what to do if there is a Widget
// which is requesting data for Virtual Pin (1)
BLYNK_READ(SETPOINT_PIN)
{
  // This command writes setpoint to Virtual Pin (1)
  Blynk.virtualWrite(SETPOINT_PIN, sp);
}

void setup()
{
  //Debug console
  Serial.begin(9600);
  
  Blynk.begin(auth, ssid, pass);
  ot.begin(handleInterrupt);  
  
  //Write initial setpoint  
  Blynk.virtualWrite(SETPOINT_PIN, sp);

  //Init DS18B20 sensor
  sensors.begin();
  sensors.requestTemperatures();
  sensors.setWaitForConversion(false); //switch to async mode
  t, t_last = sensors.getTempCByIndex(0);
  ts = millis();
  // Setup a function to be called every second
  timer.setInterval(1000L, updateData); 
}

void loop()
{
  Blynk.run();
  timer.run();
}