opentherm_thermostat/opentherm_thermostat.ino at master · ihormelnyk/opentherm_thermostat · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266mDNS.h>

#include <OneWire.h>
#include <DallasTemperature.h>

#include <OpenTherm.h>

//OpenTherm input and output wires connected to 4 and 5 pins on the OpenTherm Shield
const int inPin = 4;
const int outPin = 5;

//Data wire is connected to 14 pin on the OpenTherm Shield
#define ONE_WIRE_BUS 14

const char* ssid = "Please specify your WIFI SSID";
const char* password = "Please specify your WIFI password";

ESP8266WebServer server(80);
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
OpenTherm ot(inPin, outPin);

float sp = 23, //set point
pv = 0, //current temperature
pv_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

const char HTTP_HTML[] PROGMEM = "<!DOCTYPE html>\
<html>\
<head>\
	<meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">\
	<script>\
		window.setInterval(\"update()\", 2000);\
		function update(){\
			var xhr=new XMLHttpRequest();\
			xhr.open(\"GET\", \"/temp\", true);\
			xhr.onreadystatechange = function () {\
				if (xhr.readyState != XMLHttpRequest.DONE || xhr.status != 200) return;\
				document.getElementById('temp').innerHTML=xhr.responseText;\
			};\
			xhr.send();\
		}\
	</script>\
</head>\
<body style=\"text-align:center\">\
    <h1>OpenTherm Thermostat</h1>\
    <font size=\"7\"><span id=\"temp\">{0}</span>&deg;</font>\
    <p>\
    <form method=\"post\">\
        Set to: <input type=\"text\" name=\"sp\" value=\"{1}\" style=\"width:50px\"><br/><br/>\
        <input type=\"submit\" style=\"width:100px\">\
    <form>\
    </p>\
</body>\
</html>";

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 Kc = 10.0; // K / %Heater
	float tauI = 50.0; // sec
	float tauD = 1.0;  // sec
	// PID coefficients
	float KP = Kc;
	float KI = Kc / tauI;
	float KD = Kc*tauD;
	// upper and lower bounds on heater level
	float ophi = 100;
	float oplo = 0;
	// 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 D = -KD * dpv; //derivative contribution
	float op = P + I + D;
	// 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) + " D=" + String(D));
	return op;
}

void handleRoot() {
	digitalWrite(BUILTIN_LED, 1);

	if (server.method() == HTTP_POST) {
		for (uint8_t i = 0; i<server.args(); i++) {
			if (server.argName(i) == "sp") {
				sp = server.arg(i).toFloat();
			}
		}
	}

	String page = FPSTR(HTTP_HTML);
	page.replace("{0}", String(getTemp()));
	page.replace("{1}", String((int)sp));
	server.send(200, "text/html", page);
	digitalWrite(BUILTIN_LED, 0);
}


void handleGetTemp() {
	digitalWrite(BUILTIN_LED, 1);
	server.send(200, "text/plain", String(getTemp()));
	digitalWrite(BUILTIN_LED, 0);
}

void setup(void) {
	pinMode(BUILTIN_LED, OUTPUT);
	digitalWrite(BUILTIN_LED, 0);
	Serial.begin(115200);
	WiFi.mode(WIFI_STA);
	WiFi.begin(ssid, password);
	Serial.println("");

	// Wait for connection
	while (WiFi.status() != WL_CONNECTED) {
		delay(500);
		Serial.print(".");
	}
	Serial.println("");
	Serial.print("Connected to ");
	Serial.println(ssid);
	Serial.print("IP address: ");
	Serial.println(WiFi.localIP());

	if (MDNS.begin("thermostat")) {
		Serial.println("MDNS responder started");
	}

	server.on("/", handleRoot);
	server.on("/temp", handleGetTemp);

	server.begin();
	Serial.println("HTTP server started");

	//Init DS18B20 sensor
	sensors.begin();
	sensors.requestTemperatures();
	sensors.setWaitForConversion(false); //switch to async mode
	pv, pv_last = sensors.getTempCByIndex(0);
	ts = millis();
	ot.begin(handleInterrupt);
}

void loop(void) {
	new_ts = millis();
	if (new_ts - ts > 1000) {
		//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));
		}

		pv = sensors.getTempCByIndex(0);
		dt = (new_ts - ts) / 1000.0;
		ts = new_ts;
		if (responseStatus == OpenThermResponseStatus::SUCCESS) {
			op = pid(sp, pv, pv_last, ierr, dt);
			//Set Boiler Temperature
			ot.setBoilerTemperature(op);
		}
		pv_last = pv;
		sensors.requestTemperatures(); //async temperature request
	}
	server.handleClient(); //handle http requests
}