GLCD display wrong calculation result

[saharul]

hi,

i have problem to display a floating point with single decimal point

.........................
........................
int x=300;
float mf_err_small;
mf_err_small= (x-250)/250);

.................................

..................................
floatToStr(mf_err_small,s_temp);
Glcd_Write_Text( "small" , 5, 5, 2);
Glcd_Write_Text(s_temp, 45, 5, 2);
....................................................

the result that i got from glcd was 81.999
it supposed to display 0.2.

what went wrong?

Many thanks

[jovana.medakovic]

Hello,

Floating-point operations are not 100% accurate because some numbers cannot be represented in the IEEE format without the loss of precision. Therefore, the results of the division can end with .999999.

So, in your code, you can write:

Code: Select all

unsigned char s_temp[20] = {0};
int x = 300;
float mf_err_small;

mf_err_small = (((float)x-250)/250);
mf_err_small += 0.0000001;
  
FloatToStr(mf_err_small, s_temp);
Glcd_Write_Text( "small" , 5, 5, 2);
Glcd_Write_Text(s_temp, 45, 5, 2);

Kind regards,
Jovana

[saharul]

Thanks jovana

[jovana.medakovic]

You're welcome!

Kind regards,
Jovana