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Forum: FPGA, VHDL & Verilog Traffic light controller


Traffic light controller
von SJ O. (nicenom)

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Hi, all

I am doing a traffic light controller project with using DE2 board... 
the code I have is compiled perfectly, but when I use the DE2 board, it 
doesn't work properly... Some lights should be turned on when I switch 
on.. but for some reason it keeps having the same issues although I try 
on and on. So I asked the professor about the issue, and he said this is 
logic problem...

I hope you help me out. I attached the file of the code in case.

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Re: Traffic light controller
von Klaus (Guest)

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Does you Simulation show the same error?

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Re: Traffic light controller
von Lothar M. (Company: Titel) (lkmiller) (Moderator)

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SJ Oh wrote:
> the code I have is compiled perfectly
I can write don some lines of VHDL tha compile rperfectly well, but the 
will do nonsens on the hardware. The debugger for VHDL is the funtional 
simulator.

> but for some reason it keeps having the same issues
Which ones?

One question:
How fast is your clock?
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    elsif CLK'event and CLK = '1' then                -- how fast ....

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      case traffic_light_controller is

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        when GR =>

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          if count < sec_5 then  

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            traffic_light_controller <= GR;

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            count <= Count+1;                         -- ... will count count up?

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          else

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            traffic_light_controller <= YR;

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            count<=X"0";   --count is reset to zero

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          end if;

Is it really 1Hz?



This is not the problem, but for me it is a major mistake:
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type traffic_light_controller_type is (GR, RY, RR2, YR, RG, RR1);

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signal traffic_light_controller: traffic_light_controller_type;

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traffic_light_controller_machine: process (CLK,CLR)

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begin

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    if CLR='1' then  

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      traffic_light_controller <= GR;

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    elsif CLK'event and CLK = '1' then

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      case traffic_light_controller is

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        when GR =>

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        when YR =>

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        when RR1 =>

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        when RG =>

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        when RY =>

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        when RR2 =>

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        when others =>   -- there are no remaining other states !!!!!!

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      end case;

when others is not necessary when all of the possible states are used. 
The signal traffic_light_controller has only 6 states and each of them 
is explicitly used, so there are no "others" remaining!

  


  




  

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