need helps in coding...

[Altera_Forum]

hi i'm using an ultrasonic sensor to measure distance which produces PWM output, the pwm output is 147us/inch. i want to implement it in de2 board. 

i'm using 50MHz input clock from de2 board and the input from the sensor is 147us/inch. so 147us / 20ns = 7350 counts per inch. i'm already tried to do some coding to read the sensors output, i'm planning to use the sensor to measure distance up to 8 inch. so basically i just count the counter to 7350 to 1 inch and continue counting to 2 inch and so on. this is the coding,am i doing it right or is it violates the way to reads pwm? when i compile it using quartus there are no errors but when i use the sensor nothing happens.. anyone has any suggestion.? thank you, regards, faizul  library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.STD_LOGIC_ARITH.ALL; use IEEE.STD_LOGIC_UNSIGNED.ALL;   entity maxsonar_pwm_signal_decoder is    Port ( clk : in STD_LOGIC;  reset : in STD_LOGIC;  maxsonar_pwm : in STD_LOGIC;  y : out std_logic_vector(0 to 7);  led : out std_logic;  pwm_distance : out std_logic_vector(2 downto 0));   end maxsonar_pwm_signal_decoder;   architecture Behavioral of maxsonar_pwm_signal_decoder is   signal pwm_inches : std_logic_vector(2 downto 0); signal pwm_distance_i : std_logic_vector(2 downto 0);    begin   pwm_distance <= pwm_distance_i;    process(clk)  variable pwm_count : integer range 0 to 60000;  begin  if reset = '1' then  pwm_count := 0;  pwm_distance_i <= "000";  elsif rising_edge(clk) then   if maxsonar_pwm = '1' then    if pwm_count = 7350 then  pwm_inches <= "001";  end if;   if pwm_count = 14700 then  pwm_inches <= "010";  end if;   if pwm_count = 22050 then  pwm_inches <= "011";  end if;   if pwm_count = 29400 then  pwm_inches <= "100";  end if;   if pwm_count = 36750 then  pwm_inches <= "101";  end if;   if pwm_count = 44100 then  pwm_inches <= "110";  end if;   if pwm_count = 51450 then  pwm_inches <= "111";   else  pwm_count := pwm_count + 1;    end if;  else    if (pwm_inches > "000") then  pwm_distance_i <= pwm_inches;  end if;  pwm_count := 0;  pwm_inches <= "000";  end if;  end if;    end process;    process(pwm_inches )  begin    case pwm_inches is  when "000"=>  y<="10000000";  when "001"=>  y<="01000000";  when "010"=>  y<="00100000";  when "011"=>  y<="00010000";  when "100"=>  y<="00001000";  when "101"=>  y<="00000100";  when "110"=>  y<="10000010";  when "111"=>  y<="00000001";  when others=>  y<="00000000";    led <= '1';  end case; end process;   end Behavioral;

[Altera_Forum]

When you have a look at this section:else if (pwm_inches > "000") then pwm_distance_i <= pwm_inches; end if; pwm_count := 0; pwm_inches <= "000"; end if;The pwm_inches is reset at 000 as soon as the PWM pulse ends. You probably won't see anything on the output because of that. I think that your second process should use the pwm_distance_i signal instead, that should keep the value of the measured distance after the PWM pulse ends:process(pwm_distance_i ) begin case pwm_distance_i is when "000"=>And also in that last process, you assign led to 1 in the others section, but never to 0. If you want the led signal to be 0 when you have a valid measured distance, you can assign a default value before the case:process(pwm_distance_i ) begin led <= '0'; case pwm_distance_i is when "000"=>

[Altera_Forum]

thanks for your reply, i'm already made the correction, but still there are nothing happens to the led when i connect the sensor output to de2 board. what i concern is, am i doing the right way for reading pwm output from the sensor. this is the datasheet for the sensor i used. http://maxbotix.com/documents/mb1010_datasheet.pdf 

there are 3 type of output which is pwm, serial output and analog, but i'm need to use the pwm output.  thanks, regards, faizul

[Altera_Forum]

it looks right. I suggest to use Signaltap to check that the signal you are getting is what you expect and that the counter increments as it should.