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#include <WiFi.h>
#include <HTTPClient.h>
#include <PID_v1.h>
#define nelem(arr) (sizeof(arr) / sizeof(arr[0]))
enum {
SECOND = 1000,
PERIOD = 30*SECOND,
};
enum pins { SOLENOID_PIN = 21 };
enum tunings {
P = 2,
I = 5,
D = 1,
};
enum { SOLENOID_WINDOW = 5000 };
const char ssid[] = "Pixel_6504";
const char password[] = "zj3av9sjev7ed8j";
const char humidityUrl[] = "http://hvac.samanthony.xyz/humidity";
const char targetUrl[] = "http://hvac.samanthony.xyz/target_humidity";
const char dutyCycleUrl[] = "http://hvac.samanthony.xyz/duty_cycle";
double pidInput, pidOutput, pidSetpoint;
PID pid(&pidInput, &pidOutput, &pidSetpoint, P, I, D, DIRECT);
void
setup(void) {
pinMode(SOLENOID_PIN, OUTPUT);
Serial.begin(9600);
while (!Serial) {}
pid.SetOutputLimits(0, SOLENOID_WINDOW);
pid.SetMode(AUTOMATIC);
WiFi.begin(ssid, password);
Serial.print("Connecting to WiFi...");
while (WiFi.status() != WL_CONNECTED) {
Serial.print(".");
delay(500);
}
Serial.println(" connected.");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
}
void
loop(void) {
static float humidity = 0.0; // Measured humidity of the building.
static float target = 0.0; // Target humidity.
static unsigned long lastUpdate = 0; // Last time the server was contacted.
pidInput = humidity;
pidSetpoint = target;
pid.Compute();
writeSolenoidPin(pidOutput);
unsigned long now = millis();
if (now - lastUpdate > PERIOD) {
lastUpdate = now;
if (get(humidityUrl, &humidity) != 0)
Serial.println("Failed to get humidity from server.");
if (get(targetUrl, &target) != 0)
Serial.println("Failed to get target from server.");
float dc = pidOutput / SOLENOID_WINDOW * 100.0;
if (postDuty(dc) != 0)
Serial.println("Failed to post duty cycle to server.");
Serial.printf("Measured humidity: %.2f%%\n", humidity);
Serial.printf("Target humidity: %.2f%%\n", target);
Serial.printf("Duty cycle: %.0f%%\n", dc);
}
}
// Make a GET request to the server and set *x to the float value that it responds with.
// Return non-zero on error.
int
get(const char *url, float *x) {
if (WiFi.status() != WL_CONNECTED) {
Serial.println("WiFi not connected.");
return 1;
}
// Send request to server.
HTTPClient http;
Serial.printf("GET %s\n", url);
http.begin(url);
int responseCode = http.GET();
Serial.printf("HTTP response code: %d\n", responseCode);
if (responseCode != HTTP_CODE_OK) {
http.end();
return 1;
}
// Parse response.
int status = parseFloat(http.getString().c_str(), x);
http.end(); // Cannot be freed before parseHumidity() because response is stored in the http buffer.
return status;
}
// POST the duty cycle to the server. Return non-zero on error.
int
postDuty(float duty) {
static char url[512];
int n;
n = snprintf(url, nelem(url), "%s?%.0f", dutyCycleUrl, duty);
if (n >= nelem(url))
Serial.println("Duty cycle url string buffer overflow; truncating.");
return post(url);
}
// Make a POST request to the server. Return non-zero on error.
int
post(const char *url) {
if (WiFi.status() != WL_CONNECTED) {
Serial.println("WiFi not connected.");
return 1;
}
WiFiClient client;
HTTPClient http;
Serial.printf("POST %s\n", url);
http.begin(client, url);
int responseCode = http.POST("");
http.end();
Serial.printf("HTTP response code: %d\n", responseCode);
if (responseCode != HTTP_CODE_OK)
return 1;
return 0;
}
// Parse the value of str into *x. Returns non-zero on error.
int
parseFloat(const char *str, float *x) {
if (sscanf(str, "%f", x) != 1) {
Serial.printf("Failed to parse float: '%s'\n", str);
return 1;
}
return 0;
}
void
writeSolenoidPin(double pidOutput) {
static unsigned long windowStartTime = 0;
unsigned long now = millis();
if (now - windowStartTime > SOLENOID_WINDOW) {
// Start new window.
windowStartTime = now;
float dc = pidOutput / SOLENOID_WINDOW * 100.0;
Serial.printf("Duty cycle: %.0f%%\n", dc);
}
if (pidOutput > now - windowStartTime)
digitalWrite(SOLENOID_PIN, HIGH);
else
digitalWrite(SOLENOID_PIN, LOW);
}
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