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Topic: sprintf ? (Read 26298 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

bhavasarbhagyesh

 HEY GUYS I GOT THE ANSWER FOR, CONVERT FLOATING VALUES IN STRING USING SPRINTF(); FUNCTION   


                                      double temp = 55.55;
                      char buffer[4];

                  sprintf(buffer, "%02.02f", temp);

                  ssd1306_set_cursor(15, 26);
                  ssd1306_putstring(buffer);
                       ssd1306_display();

OUTPUT:
55.55

OldSteve

HEY GUYS I GOT THE ANSWER FOR, CONVERT FLOATING VALUES IN STRING USING SPRINTF(); FUNCTION   


                                      double temp = 55.55;
                      char buffer[4];

                  sprintf(buffer, "%02.02f", temp);

                  ssd1306_set_cursor(15, 26);
                  ssd1306_putstring(buffer);
                       ssd1306_display();

OUTPUT:
55.55
You think? You declare a 4 character array, then expect 6 characters (including the terminating null) to fit in it, for one.

And why does this print "?":-
Code: [Select]
void setup()
{
    Serial.begin(115200);
    double temp = 55.55;
    char buffer[4];
    sprintf(buffer, "%02.02f", temp);
    Serial.println(buffer);                  // Prints "?"
}

void loop(){}


Also why does this print "2":-
Code: [Select]
void setup()
{
    Serial.begin(115200);
    double temp = 55.55;
    char buffer[4];
    sprintf(buffer, "%02.02f", temp);
    Serial.println(strlen(buffer));        // Prints "2"
}

void loop(){}
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

sterretje

And all of that three years after the opening post :)
If you understand an example, use it.
If you don't understand an example, don't use it.

Electronics engineer by trade, software engineer by profession. Trying to get back into electronics after 15 years absence.

OldSteve

And all of that three years after the opening post :)
Ha. I didn't notice that. Well it took a while, but at least he got the answer. :D
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

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