How do I fix this conversion problem?

I am studying VHDL with this simple module, and the conversion between
std_logic_vector and
unsigned/signed is really troublesome!

I need all IOs to be in std_logic/vector, but inside some computations can
take on other
standards.

Thank you in advance!



# ** Error: ../RTL/channel_awgn.vhd(3: No feasible entries for subprogram
"to_bitvector".
# ** Error: ../RTL/channel_awgn.vhd(53): VHDL Compiler exiting
# C:/Programs/Modeltech_xe_starter/win32xoem/vcom failed.





library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
use IEEE.math_real.uniform;

entity channel_awgn is
port (
clk_in : in std_logic;
rstn_in : in std_logic;

conv_in : in std_logic_vector(1 downto 0);
conv_en_in : in std_logic;
snr_in : in std_logic_vector(7 downto 0);

rx_data_out : out std_logic_vector(7 downto 0);
rx_en_out : out std_logic
);
end channel_awgn;

architecture channel of channel_awgn is

begin

process(clk_in, rstn_in)
variable seed1, seed2 : positive := 1;
variable a_real : real;
variable noise : integer;
variable tmp_us: unsigned(7 downto 0);
begin
if rstn_in = '0' then
rx_data_out <= (others=>'0');
elsif rising_edge(clk_in) then
uniform(seed1, seed2, a_real);
noise := natural(a_real * real(2** - 0.5);
if (conv_en_in = '1') then
tmp_us := unsigned('0' & conv_in & b"01000") + to_unsigned(noise, ;
rx_data_out <= to_StdLogicVector(to_bitvector(tmp_us)); <========
Here is line 38.
end if;
end if;
end process;

end channel;

G Iveco

Hi,

Simply :

rx_data_out <= Std_Logic_Vector(tmp_us);

Best regards.

Alain