Display Behavior for Floating Point Numbers

Other Hardware Displays
1

I'm using the LiquidCrystal_I2C library by Mario_H and am having trouble getting the desired result. The app is timing events using the millis function and then calculating a floating point number in seconds,
i.e. Lane1ET = (Lane1StopTime - StartTime)/1000.0;

Where Lane1ET is a float, Lane1StopTime and StartTime are unsigned longs.

I'm sending the values to the display like this:

Lane1ET = (Lane1StopTime - StartTime)/1000.0;
lcd.setCursor(0,0);
lcd.print("LANE 1 ");
lcd.print(Lane1ET);

The behavior I'm getting is that only 2 places beyond the decimal are displayed. As my timing interval increases, places are added in front of the decimal but I always have 2 decimal places. I'm trying to display at least to the 3rd decimal place and 4th if possible.

I tried declaring Lane1ET as a char Lane1ET[7] but get a compile error on the first line above.

Any insight into what's going on here would be greatly appreciated.

Thanks, controlmech

2

How you declaring the variable Lane1StopTime & Start Time. if it is unsigned long int Why you are dividing by 1000.0 floating value. Why can't you divide by 1000 itself???

Just cross check it once

3

With Lane1ET declared as float, you should be able to use

lcd.print(Lane1ET,3)

lcd.print(Lane1ET,4)

If there is something in the Mario_H library blocking more than two decimal places, consider changing to the F. Malpartida library.

4

If you have fixed room for e.g. 6 digits including decimal point + sign you need to write your own formatting routine.

something like this

void myPrint(float val)
{
  int n = lcd.print((int) val);   // decimal part with sign
  int digitsLeft = max(6-n,0);

  if (digitsleft > 0)
  {
    long factor = 1;
    for (int i=0; i<digitsleft; i++) factor  *= 10;
    long frac = (val - (int) val) * factor ;  // get fraction as long
    lcd.print(".");  // decimal point
    lcd.print(frac);
  }
}
5

Cattledog, once again you have saved the day!

The ,#) at the end of the lcd.print took care of the issue.

Thanks again,
controlmech