cannot fix: warning signal clk IBUF has no load please help!

Question

I have been trying to design a simple Hardware design to controll another board that powers a set of LEDs for a stage drum lighting system. I cannot for the life of me figure out why I am recieving these warnings

In short what I am trying to do here is create a design that switches the lights color each time the Base drum (BaseBeat) is hit, with a maximum transition time of 1 light change a second (I am using a 50Mhz clock so I used a counter qtemp to count up and then reset after the BaseBeat is pressed) I have tested both the TB and the design on my Spartan3e but nothing happens (when I remove anything to do with the clock and the one second transition limit it works).

Also so far I have taken one course on VHDL and FPGA design, I will be taking more this spring, but I hope to have this working so I can set up the light system earlier.

these are the warnings

WARNING:Xst:646 - Signal  is assigned but never used. This unconnected signal will be trimmed during the optimization process.
WARNING:PhysDesignRules:367 - The signal  is incomplete. The signal
 does not drive any load pins in the design.
WARNING:Par:288 - The signal clk_IBUF has no load. PAR will not attempt to route this signal.
WARNING:Par:283 - There are 1 loadless signals in this design. This design will cause Bitgen to issue DRC warnings.

(the next_color warning does not seem to be my major problem, although I could be wrong)

Here is my code:

entity LEDcontroller is
port(   BaseBeat: in STD_LOGIC;
        output,ON_BOARD_LED_output: out STD_LOGIC_VECTOR(2 downto 0);
        color_scheme: in STD_LOGIC_VECTOR(1 downto 0); 
        ON_BOARD_LED_color_scheme: out STD_LOGIC_VECTOR(1 downto 0); 
        ON_BOARD_LED_BaseBeat: out STD_LOGIC;
        ON_BOARD_LED_ONEsec_flag: out STD_LOGIC;
         clk : in STD_LOGIC);
end LEDcontroller;

architecture controller_behavior of LEDcontroller is
type color_type is (RED, YELLOW, GREEN, TURQOISE, BLUE, PINK, WHITE, OFF); 
signal current_color: color_type := OFF;
signal next_color: color_type := OFF;   
signal outputTEMP: STD_LOGIC_VECTOR(2 downto 0);        -- default is off 
signal qtemp: STD_LOGIC_VECTOR(24 downto 0);
signal ONEsec_flag: STD_LOGIC;

begin
    process(clk)
        begin
            if (clk'event and clk='1') then
                    qtemp <= qtemp + 1;
                 end if;
    end process;

    sequence: process(current_color,color_scheme)
        begin
            if (color_scheme = "00") then
                case current_color is
                        when RED => next_color <= GREEN;

                        when GREEN => next_color <= BLUE;

                        when BLUE => next_color <= RED;

                        when OTHERS => next_color <= RED;
                end case;           
            elsif (color_scheme = "01") then
                case current_color is
                        when RED => next_color <= YELLOW;

                        when YELLOW => next_color <= GREEN;

                        when GREEN => next_color <= TURQOISE;

                        when TURQOISE => next_color <= BLUE;

                        when BLUE => next_color <= PINK;

                        when PINK => next_color <= RED;

                        when OTHERS => next_color <= RED;
                    end case;
             elsif (color_scheme = "10") then
                case current_color is
                        when RED => next_color <= PINK;

                        when PINK => next_color <= BLUE;

                        when BLUE => next_color <= TURQOISE;

                        when TURQOISE => next_color <= GREEN;

                        when GREEN => next_color <= YELLOW;

                        when YELLOW => next_color <= RED;

                        when OTHERS => next_color <= RED;
                    end case;
                else
                case current_color is
                        when RED => next_color <= BLUE;

                        when BLUE => next_color <= GREEN;

                        when GREEN => next_color <= WHITE;

                        when WHITE => next_color <= RED;

                        when OTHERS => next_color <= RED;
                    end case;
                end if;
            end process;

    transition: process(BaseBeat,qtemp)
        begin
                    if (qtemp = "10111110101111000010000000") then
                        ONEsec_flag <= '1';
                    end if;
                    if (BaseBeat'event and BaseBeat = '1') and (ONEsec_flag='1') then 
                        current_color <= next_color;
                        ONEsec_flag <= '0';
                    else 
                        current_color <= current_color;
                    end if;
                end process;

    control: process(current_color)
        begin
                case current_color is 
                    -- main colors
                    when RED => outputTEMP <= "110"; 
                    when GREEN => outputTEMP <= "101";
                    when BLUE => outputTEMP <= "011";
                    --extended colors
                    when YELLOW => outputTEMP <= "100";
                    when TURQOISE => outputTEMP <= "001";
                    when PINK => outputTEMP <= "010";
                    --all or nothing
                    when WHITE => outputTEMP <= "000";
                    when OTHERS => outputTEMP <= "111";
                end case;
        end process;    

        --components
        --main outputs
        output <= outputTEMP;
        -- on board led outputs
        ON_BOARD_LED_output <= outputTEMP;
        ON_BOARD_LED_color_scheme <= color_scheme;
        ON_BOARD_LED_BaseBeat <= BaseBeat;  
        ON_BOARD_LED_ONEsec_flag<=ONEsec_flag;
end controller_behavior;

and my UCF:

# Clocks
NET "clk" LOC = " B8 " ;#Bank = 0, Signal name = MCLK


# Pin assignment for LEDs
NET "ON_BOARD_LED_output" LOC = "G1" ; # Bank = 3, Signal name = LD7
NET "ON_BOARD_LED_output" LOC = "P4" ; # Bank = 2, Signal name = LD6
NET "ON_BOARD_LED_output" LOC = "N4" ;  # Bank = 2, Signal name = LD5

NET "ON_BOARD_LED_BaseBeat" LOC = "P6" ; # Bank = 2, Signal name = LD3

NET "ON_BOARD_LED_color_scheme" LOC = "M11" ; # Bank = 2, Signal name = LD1
NET "ON_BOARD_LED_color_scheme" LOC = "M5" ;  # Bank = 2, Signal name = LD0
NET "ON_BOARD_LED_ONEsec_flag" LOC = "P7" ;  # Bank = 2, Signal name = LD5

NET "color_scheme" LOC = "L3";  # Bank = 3, Signal name = SW1
NET "color_scheme" LOC = "P11";  # Bank = 2, Signal name = SW0

NET "BaseBeat" LOC = "A7";  # Bank = 1, Signal name = BTN3




# Loop Back only tested signals
#NET "BaseBeat" LOC = "C6"  | DRIVE = 2  | PULLUP ; # Bank = 1, Signal name = JA1
NET "output" LOC = "B6"  | DRIVE = 2  | PULLUP ; # Bank = 1, Signal name = JA2
NET "output" LOC = "C5"  | DRIVE = 2  | PULLUP ; # Bank = 1, Signal name = JA3
NET "output" LOC = "B7"  | DRIVE = 2  | PULLUP ; # Bank = 1, Signal name = JA4
#NET "BaseBeat" CLOCK_DEDICATED_ROUTE = FALSE; 
 

Sorry that this is long, please help me though if you are able to, I have given myself several headaches reading my book and searching the forums all to no avail.
Thanks in advance, Scott

EDIT:

in response to my own comment to @Paebbels' suggestions

@Paebbels I do have a new issue now, even after a second has passed the transition does
not always occur when BaseBeat is pressed. When I hold BaseBeat down for a long time, the 
lights start transiting every second, but when I quickly press them even after a second it
 does not always transition, only some times. Oddly enough, if I press the BaseBeat for say
 1/2 a second it doesn't always transition either? (I thought it may have something to do 
with rising_edg(clk) and BaseBeat not occurring at the same time, but rising_edg(clk) occurs
 25M times in half a second..) Thanks again

I altered the suggested statement:

ONEsec_flag <= '1' when (qtemp = 49999999) else '0';

to be:

process(clk)
            begin
                if rising_edge(clk) then
                    if (qtemp = 49999999) then ONEsec_flag <= '1';
                    elsif (BaseBeat='1') then ONEsec_flag <= '0';
                    else ONEsec_flag <= ONEsec_flag;
                    end if;
                end if;
        end process;

Is this good design practice? it seems to be working now (it transitions after a second regardless of how long or fast I press the BaseBeat) and I think I made it synchronous, at least within my understanding of synchronous.

Thanks for all the help guys, especially you @Paebbels! have a Happy New Year!

Answer 1

Some hints for and questions to your code:

• signal nextColor should not have a default value, because it's not mapped to a register
  signal nextColor : color_type;
• signal qtemp misses a default value: it's a counter/mapped to a register
• secondly, this signal represents a counter and it's used in arithmetic calculations. So qtemp should be of type (un)signed or integer/natural. Doing artithmetic calculations on std_logic_vector is not a recommended style.
  signal qtemp : unsigned(24 downto 0) := (others => '0');
• qtemp should also be reset to 0 after 1 second passed by (as David Koontz wrote in the comment below)
• if you change the type of qtemp you can rewrite the test (qtemp = "10111110101111000010000000") to (qtemp = 50000000)
  Actually, it should be 49,999,999, because your counter starts at 0.
• ONEsec_flag is asynchronous set and synchronous reset -> try to write full synchronous design.

• line if (BaseBeat'event and BaseBeat = '1') and (ONEsec_flag='1') then can and will cause several problems:

  1. BaseBeat is no clock signal, but you are using this signal as a clock. A better solution would be to use BaseBeat as an (clock)enable signal.
  2. writing a rising edge condition and a clock enable in one line is no good style. Additionally it can cause synthesis tools to infer wrong hardware.

  3. In combination with your else-statement this code will not be synthesizable. Here is a solution:

     calculating the flag (concurrent statement):
     ONEsec_flag <= '1' when (qtemp = 49999999) else '0'; -- ternary operator like ?: in C

     transition process:

     transition: process(clk)
     begin
       if rising_edge(clk) then         -- synchronous design using the main clock    
         if (BaseBeat = '1') then       -- using BaseBeat as an clock enable
           if (ONEsec_flag='1') then    -- using flag as an write enable (second ce)
             current_color <= next_color;
           end if;
         end if;
       end if;
     end process;
     

• So now, flag is calculated concurrently, it can be used to reset the second timer, otherwise a 25 bit vector will overflow after 2^25 cycles, that are 33554432:

  process(clk)
  begin
    if (clk'event and clk='1') then
      if (ONEsec_flag = '1') then      -- synchronous reset if one second is reached
        qtemp <= (others => '0');
      else
        qtemp <= qtemp + 1;
      end if;
    end if;
   end process;
  

• this leads us to another problem: your counter signal has insufficient bits to hold 49,999,999 -> you need at least 26 bits

• the UCF file has several errors:

  1. NET "clk" ... has another signal name in comment
  2. one signal can not have multiple locations

  3. ON_BOARD_LED_output is a vector, so you should access each bit by using netname<index> and assign a location for each bit.

     NET "ON_BOARD_LED_output<2>" LOC = "G1" ; # Bank = 3, Signal name = LD7
     NET "ON_BOARD_LED_output<1>" LOC = "P4" ; # Bank = 2, Signal name = LD6
     NET "ON_BOARD_LED_output<0>" LOC = "N4" ; # Bank = 2, Signal name = LD5
     

  4. NET "output" ...: Why have you enabled internal pullup resistors (inside the IOB)? Most development boards have them externally.

  5. and why are you limiting the current to 2 mA (DRIVE = 2)?
  6. All pins have no assigned IOSTANDARD: This is needed for a proper timing analysis. If you want to switch to newer FPGAs and tools, it's then absolutely necessary to declare an IOSTANDARD