getting data from arduino and stored in database t

问题:

I am getting data from arduino and stored in database through ethienet. But when i got value ambientemp from arduino. it showed correct value when i tested on serial monitor. but when I use sprintf() I got -3275 or 0 value, which it is not correct value. Here is my partial code in sketch, please help...Here is guy doing his project. The result on Sketch serial montior is: ambientTemp 23.55 and then GET /getData/temp.php?t=-3278 I copied some of him: getting data and stored it into mysql

void getData() {
  double ambientTemp=23.55; //to make it easy I assign ambientTemp a value.
unsigned long previousMillis = 0;
unsigned long currentMillis = 0;
long interval = 10000; 
  char strURL[70];


   EthernetClient client;
  // If there's a successful connection, send the HTTP POST request
   currentMillis = millis();
  if(currentMillis - previousMillis > interval) {
    previousMillis = currentMillis;

  if (client.connect(server, 80)) {
    Serial.println("get data connecting...");

    //client.println("GET /getData/temp.php?t=%d,temp HTTP/1.1");
   // delay(10000);
     Serial.println("ambientTemp");
  Serial.println(ambientTemp);
    sprintf(strURL,"GET /getData/temp.php?t=%d",ambientTemp);
    delay(50000);

    client.print(strURL);
    client.println();
   // client.print(strURL);
    Serial.print(strURL);



  } 
  else {
    // If you couldn't make a connection:
    Serial.println("Connection failed");
    Serial.println("Disconnecting.");
    client.stop();
  }
}
}

回答1:

You need to read up on C format specifications. "%d" means take the corresponsding variable (ambientTemp in your case) and interpret it as an integer. So what the runtime code is doing is looking at the bytes which make up your double, and interpreting the first 2 of those an in integer. Not what you want.... use "%f" as a format specifier...