LED Blinking: Troubleshooting Help Needed!

General
1

I am trying to turn on one LED for x amount of time before cycling to the next LED and so on, but I have been unable to do so. Can someone help?

In terms of the code, I am trying to power br_pin[0] for x time, then turn it off and power br_pin[1] and so on, until I reach br_pin[3], from where I will cycle back to turn on br_pin[0]

Here is my code; all help is appreciated!!

module au_top (
    input clk,              // 100MHz clock
    input rst_n,            // reset button (active low)
    input usb_rx,           // USB->Serial input
    output usb_tx,
    output br_pin[8]
  ) {
  
  sig rst;
  
  .clk(clk) {
    // The reset conditioner is used to synchronize the reset signal to the FPGA
    // clock. This ensures the entire FPGA comes out of reset at the same time.
    reset_conditioner reset_cond;     
    .rst(rst) {
      counter myCounter;
      dff tmr[28];
    
    }
  }
  
   always {
    tmr.d = tmr.q + 1;
    reset_cond.in = ~rst_n; // input raw inverted reset signal
    rst = reset_cond.out;   // conditioned reset
    usb_tx = usb_rx;        // loop serial port
    br_pin = 8x{8h00};
    
    if(tmr.q[27] == 1){
         br_pin[myCounter.value] = 8hFF;
    }
  }
}

module counter (
    input clk,      // clock
    input rst,      // reset
    //output on_status,
    output value // current value
  ) {
  
  .clk(clk), .rst(rst) {
    dff val;     // value storage
    
    
  }
  always {
     val.d = 0;
     if (val.q == 4)        // if max value
        val.d = 0;           // reset to 0
     else                   // otherwise
        val.d = val.q + 1;   // add one
     
    value = val.q;


  }
}

I know I have initiated the Br pins correctly because I have tested them!

2

It looks like you are using the br_pin like it’s a table of 8 8-bit value, but it’s actually a table of 8 individual bits.

br_pin = 8x{8h00};

should be

br_pin = 8h00;

and

br_pin[myCounter.value] = 8hFF;

should be

br_pin[myCounter.value] = 1;
4

Is that the only problem? Because I don’t think the cycling counter module works properly either, but I don’t know what is wrong with it…

5

The counter module looks fine but it’s clocked with the 100 MHz clock so it’s counting veeeeeeeery fast.

If you want it to count along with the timer, I think you could feed it with tmr.q[26] as its clock instead of the 100 MHz.

6

That worked!! Thank you so much!! That also explains why every LED was turning on at once lmaoo

7

You should generally not use non-clock signals as clocks. This will almost certainly lead to issues at some point due to timing.

Instead you should clock counter off the main clock but only increment it when the conditions are right. In this case you could use if (&tmr.q) which would only be valid when tmr.q is maxed out.

If you’re using a power of 2 prescaler, you can do this even cleaner but just using a bigger dff. See the built in counter module as an example