Log 5 - Blinking LED

Let's start with the basics - an LED blinker for a dev board with a built-in LED.
This is equivalent to the following code on Arduino:

void setup() {
    pinMode(LED_BUILTIN, OUTPUT);
}
void loop() {
    digitalWrite(LED_BUILTIN, HIGH);
    delay(1000);
    digitalWrite(LED_BUILTIN, LOW);
    delay(1000);
}
                

• Write SystemVerilog code equivalent to the Arduino code above.
• Figure out where the LED and clock are on the FPGA board.
• Update the assignment editor with those pins.
• Compile the SV file and bug-test it until it compiles
• Flash the compiled bitstream to the FPGA board
• Fix the code until it blinks the LED on the FPGA board

SystemVerilog Code

// LED Blinking module

module blinkLED ( //define signals for blinkLED (Inputs & Outputs)
    input  logic clk,		// clock input
    input  logic rst_n,    // active LO reset input
    output logic led			// LED output
); 

// 50 MHz clock speed -> 25,000,000 cycles = 0.5 sec blink rate
localparam int MAX_COUNT = 25_000_000;

// Create a logic vector called 'counter'
// the width is equal to the ceiling of log base 2 of N-1
// which is the way of determining the number of bits to store MAX_COUNT
logic [$clog2(MAX_COUNT)-1:0] counter;

// Create a flip-flop that updates on the rising edge of CLK or falling edge of RST_N
always_ff @(posedge clk or negedge rst_n) begin
    // if reset is LO, reset the state
    if (!rst_n) begin
        counter <= 0;
        led     <= 0;
    end
    // else, (reset is HI), run normal operation
    else begin
        // If the counter reaches the max state, then
        if (counter == MAX_COUNT - 1) begin
            counter <= 0;			 // reset counter, and
            led     <= ~led;      // toggle LED
        end
        // If the counter has not reached the max state, increment it
        else begin
            counter <= counter + 1;
        end
    end
end
endmodule // end of blinkLED module
                

Pins

Compilation

Programming

Results