Frequency divider for infrared output

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devsan

Joined: 04 Nov 2009
Posts: 1

04 Nov 2009 20:16 Frequency divider for infrared output

Hi I need to divide my frequency from 1MHz to 38kHz, will this code help me do that?

entity test is
port( clk:in bit; clkout:out bit);
end test;

architecture behavior of test is
begin
process(clk)
variable cnt : integer range 0 to 26;
begin
if(clk'event and clk='1') then
if(cnt=26)then
cnt:=0;
clkout<='1';
else
cnt := cnt+1;
clkout<='0';
end if;
end if;
end process;
end behavior;

This should give me a frequency of 38,5kHz will this work for an IR transmitter?

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FvM

Joined: 22 Jan 2008
Posts: 5161
Helped: 767
Location: Bochum, Germany

04 Nov 2009 21:07 Re: Frequency divider for infrared output

Look sharp, the divider factor is 27 rather than 26 in your code, but 26 would be better. Furthermore, you should provide a 50% duty cycle square wave.

Code:

begin
if(clk'event and clk='1') then
if(cnt=12)then -- divide by 13
cnt:=0;
clkout<=NOT clkout; -- divide by 2, generate square wave
else
cnt := cnt+1;
end if;
end if;

Usual RC receivers have about 10-15% relative bandwidth, 38.5 kHz would cause no relevant sensitivity drop.