Re: frequency meter on cyclone IV E ,without display frequency

Altera_Forum · ‎08-21-2017

hi everybody.

sorry for my english.

I ask for your help for released an simple frequency meter with vhdl (i am newbie on FPGA):

https://alteraforum.com/forum/attachment.php?attachmentid=14027&stc=1

Input

"ref_clock" is 50 MHz periode 20ns of cyclone IV E.

"signal" is mesured signal from encoder

Output

cycle of test errors every 1 sec

if frequency >= 1000 Hz ==>error1 = 1 //1 is logic HIGH

if frequency >= 2000 Hz ==> error1 = 1 and error2 = 1

else error1 = 0 and error2 = 0 //0 is logic LOW

thank you.

Altera_Forum · ‎08-21-2017

What help do you need. What problems are you having?

Altera_Forum · ‎08-21-2017

try google: fpga vhdl frequency measure

(hint: the second hit may be this one: http://surf-vhdl.com/compute-frequency-clock/)

Altera_Forum · ‎08-21-2017

thank you Tricky, josyb.

Tricky, how to do it in the simplest way possible.

josyb, I didn't understand half of the code.

I told you that I was newbie in(FPGA VHDL...)

Here is my code


library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity freq_meter is
port (
  i_ref_clock    : in  std_logic; -- 50 MHz
  i_signal       : in  std_logic; -- from encoder
  o_error1       : out std_logic; 
  o_error2       : out std_logic);
end freq_meter;
architecture freq_meter_arch of freq_meter is
begin
--  CLOCK REFERENCE domain
variable clock_secand_decounter : integer := 50000000;
variable i_signal_counter : integer := 0;
if(clock_secand_decounter<=1) then
	if(rising_edge(i_signal)) then
		i_signal_counter <=i_signal_counter+1;
  		if(rising_edge(i_ref_clock)) then
			clock_secand_decounter <= clock_sec_dec -1;
		end if;
	end if;
end if;
if(clock_secand_decounter >= 1000)then
	o_error1='1';
	o_error2='0';
	elsif(clock_secand_decounter >= 2000)then
	o_error1='1';
	o_error2='1';
else
	o_error1='0';
	o_error2='0';
end if;
end freq_meter_arch;

Yes I know there is a lot of errors

Here is the timeline.

https://www.alteraforum.com/forum/attachment.php?attachmentid=14030

Altera_Forum · ‎08-22-2017

The syntax errors should be easy enough for you to fix by referencing a vhdl text book.

But there are more fundamental errors - eg. Having a rising edge inside a rising edge will never occur in reality. I suggest you work through a tutorial that covers basic logic to try and understand what is wrong with your code.

Altera_Forum · ‎08-22-2017

ok.

Tricky, thanks for the advice.