please help !

0.02 is a real, so you need to first cast the integers to reals, then back to integer:

distance <= integer( real(echo_width) * (0.02 / 58.0) );

But, remember that real types are not synthesisable, so I assume this is just testbench code.

first of all - thank you very much for help !

secondly - it is for synthesis , what can i do in this case ?

so if its for synthesis - dont use real types. You can only use reals for set up information, not runtime arithmatic. Have a look into the fixed point packages.

www.vhdl.org/fphdl

is it synthesisable ?

i defined an integer variable called "temp_distance" ,changed echo_width to a variable and used it like that :

temp_distance:=integer(real(echo_width) * (0.02 / 58.0));

distance<=temp_distance;

reminder :

distance : out integer ; (entity port)

echo_width : variable integer;

temp_distance: variable integer;

Hi

your output is integer so whatever the real data you get the decimal point digits will be truncated to integer

so you have to find the nearest integer number to the real one

for instance if we have the following operation:

out = num * 0.05;

you can find that 0.05 is nearly 13/256 (0.05078)

so first multiply num by 13 and the division is simply removing the 8 digits from the right the right

note that using integer is the same of std_logic_vector(31 downto 0) which is more flexible

you can try this :

signal num:std_logic_vector(31 downto 0);

signal temp:std_logic_vector(35 downto 0);

signal out1:std_logic_vector(31 downto 0);

num <= x"0000028E"; -- test value 654

temp<=num * x"d"; -- 654 * 13 = 8502

out1 <= "00000000"&temp(31 downto 8);-- 8502 / 256 = 33

this result 33 is near to 654 * 0.05 = 32.7

this what I do to deal with float numbers

did you got it?

yes i did . i will try that...

thank you very much !!!