nextpnr/ice40/icebreaker.v

module icebreaker (
	input  clki,
	input  btn1,
	input  btn2,
	input  btn3,
	input  btn_n,

	output led1,
	output led2,
	output led3,
	output led4,
	output led5,
	output ledr,
	output ledg,
);
    wire clk;
	SB_GB clk_gb(.USER_SIGNAL_TO_GLOBAL_BUFFER(clki), .GLOBAL_BUFFER_OUTPUT(clk));
	localparam BITS = 5;
	localparam LOG2DELAY = 22;

	reg [BITS+LOG2DELAY-1:0] counter = 0;
	reg [BITS-1:0] outcnt;

	always @(posedge clk) begin
		counter <= counter + 1;
		outcnt <= counter >> LOG2DELAY;
	end
	assign {led1, led2, led3, led4, led5} = outcnt ^ (outcnt >> 1);

    assign {ledr, ledg} = ~(!btn_n + btn1 + btn2 + btn3);
endmodule