ThingSpeak-ArduinoExample-Wifi

 #include <WiFi.h>
 #include <SPI.h>

char thingSpeakAddress[] = "api.thingspeak.com";
String writeAPIKey = "[chave_de_escrita]";
const int updateThingSpeakInterval = 17 * 1000;

char ssid[] = "[nome_da_rede]";
char pass[] = "[senha_da_rede]";

int status = WL_IDLE_STATUS;
WiFiClient client;
String stringVal = "";

long lastConnectionTime = 0;
boolean lastConnected = false;
int failedCounter = 0;

void setup() {
  Serial.begin(115200);

  while (status != WL_CONNECTED) {
    Serial.print("Conectando...");
    status = WiFi.begin(ssid, pass);
    delay(5000);
  }

  Serial.println("Conexão realizada com sucesso!");
}

void loop() {

  while (client.available()) {
    char c = client.read();
    Serial.print(c);
  }

  if (!client.connected() && lastConnected ) {
    Serial.println("...disconnected");
    Serial.println();
    client.stop();
  }

  if(!client.connected() && (millis() - lastConnectionTime > updateThingSpeakInterval))
    updateThingSpeak("field1=teste");
  lastConnected = client.connected();
}

void updateThingSpeak(String  tsdata) {
  if (client.connect(thingSpeakAddress, 80)) {
    client.print("POST /update HTTP/1.1\n");
    client.print("Host: api.thingspeak.com\n");
    client.print("Connection: close\n");
    client.print("X-THINGSPEAKAPIKEY: "+writeAPIKey+"\n");
    client.print("Content-Type: application/x-www-form-urlencoded\n");
    client.print("Content-Length: ");
    client.print(tsdata.length());
    client.print("\n\n");
    client.print(tsdata);
    lastConnectionTime = millis();

    if (client.connected()) {
      Serial.println("Conectando ao ThingSpeak...");
      Serial.println();
      failedCounter = 0;
    } else {
      failedCounter++;
      Serial.println("Connexão ao ThingSpeak falhou ("+String(failedCounter, DEC)+")");
      Serial.println();
    }

    lastConnectionTime = millis();
  }
}