Error in Sprintf not displaying floating numbers

Projects General Guidance
1

Hello everyone,

I m using this code,

char aux_str[100];
char frame[200];
void setup() {
Serial.begin(9600);
}

void loop() {
// put your main code here, to run repeatedly:
float Latitude,Longitude;
int yy,mo,dd,hh,mm,ss;
Latitude=90.5667;
Longitude=56.7764;
yy=2015;
mo=06;
dd=01;
hh=10;
mm=57;
ss=45;

sprintf(aux_str, "AT+HTTPPARA="URL","http://www.nanosoftremote.com/vts/API/startTrip.php?");
//Serial1.print(aux_str);
Serial.print(aux_str);
sprintf(frame, "B=6&R=1&SLAT=%f&SLNG=%f&T=%d/%d/%d %d:%d:%d",Latitude,Longitude,yy,mo,dd,hh,mm,ss);
//Serial1.print(frame);
Serial.println(frame);
delay(5000);
}

And getting output

AT+HTTPPARA="URL","http://www.nanosoftremote.com/vts/API/startTrip.php?&B=6&R=1&SLAT=?&SLNG=?&T=2015/6/1 10:57:45

Can anybody tell me why i am getting "?" in place of floating number
Thanks in advance

2

Hi, sprintf() does not support printing floats. I understand it was removed from the standard C library for Arduino because it made compiled sketches very large.

Also please always use code tags when you post your code, so it looks like this

Paul

3

You can use "dtostrf" instead, or reinstate float support for sprintf.
The former is easier.

4

This will use less RAM and generate less code as well.
It can be made to run on an ATtiny85 if the ledPin and timing numbers are changed.

-- my Arduino 1.6.1 compiler set for UNO board says:
Sketch uses 4,696 bytes (14%) of program storage space. Maximum is 32,256 bytes.
Global variables use 221 bytes (10%) of dynamic memory, leaving 1,827 bytes for local variables. Maximum is 2,048 bytes.

It will send the message every 5 seconds while blinking a status led and echoing user input just to show how not to block multiple tasks with a delay in one. When no task blocks execution, AVR is capable of running many tasks smoothly using a small part of the total capability. It can be slowed down to use less power and lower voltage and still do more than most beginners can believe.

void setup() {
  Serial.begin(115200); // serial chars will transmit faster, the output buffer is only 64 chars
}

void loop() {
  // put your main code here, to run repeatedly:
 static float Latitude,Longitude;
 static int yy,mo,dd,hh,mm,ss;

 static byte ledPin = 13;
 static byte ledState;

 static unsigned long lastTime;
 static unsigned long blinkTime;

 Latitude=90.5667;
 Longitude=56.7764;
 yy=2015;
 mo=06;
 dd=01;
 hh=10;
 mm=57;
 ss=45;


 if ( millis() - lastTime >= 5000UL ) { // runs once every 5 seonds
  lastTime += 5000UL;

  Serial.print( F("AT+HTTPPARA=\"URL\",\"http://www.nanosoftremote.com/vts/API/startTrip.php?"));
  Serial.print( F("B=6&R=1&SLAT="));
  Serial.print( Latitude );
  Serial.print( F("&SLNG="));
  Serial.print( Longitude );
  Serial.print( F("&T=" ));
  Serial.print( yy );
  Serial.print( F("/" ));
  Serial.print( mo );
  Serial.print( F("/" ));
  Serial.print( dd );
  Serial.print( F(" "));
  Serial.print( hh );
  Serial.print( F(":"));
  Serial.print( mm );
  Serial.print( F(":"));
  Serial.print( ss );
 }


 if ( Serial.available()) {
  Serial.print( Serial.read()); 
 }

 if ( millis() - blinkTime >= 1000UL ) { // 1 second status blink
  lastTime += 1000UL;
  ledState = !ledState; // reverses ledState between true and false, ! is logical NOT
  digitalWrite( ledPin, ledState );
 }

}