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Topic: sprintf ? (Read 18215 times) previous topic - next topic

Bertil_Lindstrom

Hello !
I am new in C++ and Arduino.

I want to use sprintf for make a string for displying on a LED-display.
But I have problems with the "format" string.
I have tried "sprintf(A_ans, "%02d %02d %02.2f",I_grader,I_min,F_sec);"
The first two numbers is ok, "%02.2f" is giving me hard time ]:)

I sure there is a simlpe answer.

/Bertil



AWOL

Because it isn't implemented.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

DeepZ

As AWOL indicated, the stdlib (i think it is stdlib) linked in by Arduino does not support floats in the sprintf.
One way around this would be to tinker with Arduino IDE to include the full/extended stdlib to get the float working in sprintf.
Another way is to convert the float using :
    dtostrf(floatVar, minStringWidthIncDecimalPoint, numVarsAfterDecimal, charBuf);

Example :
Code: [Select]

  void setup() {
    Serial.begin(19200);
  }

  void loop() {
    float F = 1.25;
    char buffer[16];
 
    dtostrf(F,5,2,buffer);
    Serial.print("Float : ");
    Serial.println(buffer);
 
    //Do not loop
    while(true) {};
  }

bperrybap


Because it isn't implemented.


Actually it is implemented in the AVR gcc toolset. It is just that the sprintf() provided by default in the AVR libc.a
does not have floating point support (to keep things smaller)
and the Arduino IDE does not allow setting the needed linker options to
to use the floating point version.

See my comments in this thread for full details and how to work around it:
http://arduino.cc/forum/index.php/topic,124809.0.html

--- bill

Bertil_Lindstrom

:D
Tks, Bill - I work with Windoz 7.
It worked after some trial_error - "by hand".

/Bertil

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