uart-test/top.v

// Simple test of the UART pins and clock, no CPU needed

module top(input clk, output ser_tx, input ser_rx, output [13:0] led);
    //assign ser_tx = test_chars; // uncomment for a bunch of ASCII "U" characters
    assign ser_tx = ser_rx; // uncomment first for serial echo

    assign led = 'b11111111111110;
    
    wire serclk;
    reg test_chars;

    clkdiv clock_generator (clk, serclk);

    always @(posedge serclk) begin
		test_chars = !test_chars;
	end
endmodule

module clkdiv(input clock_in, output reg clock_out);
    reg[15:0] counter=16'd0;
    parameter DIVISOR = 16'd104; //set according to desired baudrate for test characters (e.g. 12,000,000 Hz / 115200 baud ~= clock divider 104)

    always @(posedge clock_in) begin
        counter <= counter + 16'd1;
        if(counter>=(DIVISOR-1))
            counter <= 16'd0;

        clock_out <= (counter<DIVISOR/2)?1'b1:1'b0;
    end
endmodule