sprintf .... why it does not work?

Projects Programming
1

Hello,

I'm trying this:

char buffer[50];
unsigned long tempo = 0;

.....

void loop(void) {
.......
tempo = millis();
sprintf( buffer , "%01d:%02d.%02d", tempo / 60000 , tempo / 1000 % 60, tempo % 1000 / 10 );
Serial.println(buffer);
.....
}

I see this on the serial monitor:

for example
2:00.23
2 is minute and is correct
:
00 is always zero, is not correct
.
23 is second, the position is not correct, must before the dot

Instead I should see this:

M:SS.MS

%01d = M one char minute with zero
:
%02d = SS two char Second with zero
.
%02d = MS two char MilliSecond with zero

Why? Can someone help me?

2

%d expects an int parameter, you need %ld for a long.

3

Hy oqibidipo,

YES super Thank You :slight_smile:

4

The sprintf() function is very powerful, but rarely does an app use all of that power. In the code below, the sprintf() version uses 3450 bytes while the non-sprintf() version uses 2136 bytes.

char buffer[50];
unsigned long tempo = 0;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
}

void loop(void) {

  tempo = millis();
  //sprintf( buffer , "%01d:%02ld.%02ld", tempo / 60000L , tempo / 1000L % 60L, tempo % 1000L / 10L);
  //Serial.println(buffer);
  Serial.print(ltoa(tempo / 60000L, buffer, 10));
  Serial.print(":");
  Serial.print(ltoa(tempo / 1000L % 60L, buffer, 10));
  Serial.print(".");
  Serial.println(ltoa(tempo % 1000L / 10L, buffer, 10));

}

While the savings makes no difference in this test, if you find yourself up against memory limits down the road, try the simpler functions.

5

Hi econjack,

very interesting, thank you so much 8)