Need help with variable in a function

Projects Programming
1

I am trying to add the "fan" variable to this GET statement. But I have no idea how to get the code to compile. I know I need to declare the fan variable but I am not sure what it should be or what is the correct way to do it. The value will be "ON" "Off" and "--".

Not the full code but should be most of it.
The area in question is:

client.println("GET /tower/send_email.php?tempe="+temperature+"&humidity="+humidity+"&key=****&fan="+f+" HTTP/1.1"); //Send data

float temperature;
float humidity;

#define DHTPIN 5  

#define DHTTYPE DHT22 
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  dht.begin();
  delay(2000);
  Serial.begin(115200);
  Serial.println("Connecting");
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(100);
  }
  Serial.println("Connected");
  delay(1000);
  readSensor();
  String temperatureString = String(temperature,1);
  String humidityString = String(humidity,1);
  String fanString = String(f,1);
  //String fanString = String(fan,1);
  sendDataToServer(temperatureString,humidityString,f);
}

void loop() {

}

void sendDataToServer(String temperature, String humidity, ??? )
{
 if (client.connect(servername, 80)) {  //starts client connection, checks for connection
    Serial.println("connected");
    client.println("GET /tower/send_email.php?tempe="+temperature+"&humidity="+humidity+"&key=****&fan="+f+" HTTP/1.1"); //Send data
    Serial.println("GET /tower/send_email.php?tempe="+temperature+"&humidity="+humidity+"&key=****&fan="+f+" HTTP/1.1"); //Send data
    client.println("Host: alsconnect.com");
    client.println("Connection: close");  //close 1.1 persistent connection  
    client.println(); //end of get request
  }
2 
float temperature;
float humidity;

you have declared these 2 variables though nowhere do you initialize them so their value (although probably 0) is undetermined when you create these 3 Strings

String temperatureString = String(temperature,1);
  String humidityString = String(humidity,1);
  String fanString = String(f,1);

you will need to declare f before it compiles.
When you are trying to send it it makes sense to just keep passing "String' to the function.sendDataToServer(temperatureString,humidityString,fanString);
so you should declare that in the functionvoid sendDataToServer(String temperature, String humidity, String fan ) and then add that to the 'get command String' client.println("GET /tower/send_email.php?tempe="+temperature+"&humidity="+humidity+"&key=****&fan="+fan+" HTTP/1.1"); //Send data Does that make sense ?

Not the full code but should be most of it.

That is probably why the variables weren't visibly initialized.

3

I don't understand

String temperatureString = String(temperature,1);
  String humidityString = String(humidity,1);
  String fanString = String(f,1);

Must they be declared before the function or can it be done when the function is created?

void sendDataToServer(String temperature, String humidity, String fan )
4

Must they be declared before the function or can it be done when the function is created?

Both ! First you convert a 'float' variable (humidity) to a 'String' (humidityString)String humidityString = String(humidity,1); and when you pass it as an argument to the function heresendDataToServer(temperatureString,humidityString,fanString); it has to be declared as an argument here void sendDataToServer(String temperature, String humidity, String fan ) Anyway i suggest you read up a bit on functions in C++. Googling may provide you with some answers but i think a chapter of a book with a full explanation would be better.

5

Deva_Rishi:

float temperature;

float humidity;


you have declared these 2 variables though nowhere do you initialize them so their value (although probably 0)

Not "probably", but "is".

They're globals; they're initialised before setup() runs, even before the hidden main() runs.

6

Not "probably", but "is".

Undefined is undefined and undefined is not the same as zero.

7

No, it definitely is zero.
crt0 guarantees it that globals and statics, not assigned another value, will be initialised to zero.