//License: GPLv3
module top(input hwclk, output LED1, output LED2, output LED3, output LED4, output LED5, output ftdi_tx, input ftdi_rx, output ext_tx, input ext_rx);
	/* ~4800Hz clock (12MHz source clock) */
	reg clk_4800 = 1'b0;
	reg [10:0] cntr_4800 = 11'b0;
	parameter period_4800 = 1250;

	/* turn LED's 1-3 off */
	reg offleds = 1'b0;
	assign LED1 = offleds;
	assign LED2 = offleds;
	assign LED3 = offleds;

	/* LED 4-5 is for rx and tx */
	reg ledrx = 1'b0;
	reg ledtx = 1'b0;
	assign LED4 = ledrx;
	assign LED5 = ledtx;

	/* can't write directly to wires, so assign to registers */
	reg tx = 1'b0;
	assign tx = ext_tx;
	reg rx = 1'b0;
	assign rx = ftdi_tx;

	/* generate reduced clocks and also loopback uart at 12MHz */
	always @ (posedge hwclk) begin
		/* ~4800Hz clock */
		cntr_4800 <= cntr_4800 + 1;
		if (cntr_4800 == period_4800) begin
			clk_4800 <= ~clk_4800;
			cntr_4800 <= 11'b0;
		end

		/* just tx and rx and the full 12MHz clock - let the
		 * bitbanging software decide on the clock (just works for
		 * unknown reasons) */	

	       /* get a bit from ftdi_rx (i.e. input coming from the computer
	        * and pass it to the external tx port */
		tx <= ftdi_rx;

		/* get a bit from the external rx port and pass it to ftdi_tx
		 * (i.e. bit to the computer)*/
		rx <= ext_rx;
	end

	/* blink leds if we just txed - 1/2 of clock rate of the main loop prevents LEDs from blinking too fast */
	always @ (posedge clk_4800) begin
		if (ftdi_rx == 0) ledrx <= ~ledrx;
		if (ftdi_tx == 0) ledtx <= ~ledtx;
	end

endmodule