`timescale 1 ns / 1 ps

module hdl4se_uart_ctrl_axi
(
		input wire			s00_axi_aclk,
		input wire			s00_axi_aresetn,
		input wire [3 : 0]	s00_axi_awaddr,
		input wire [2 : 0]	s00_axi_awprot,
		input wire			s00_axi_awvalid,
		output wire			s00_axi_awready,
		input wire [31 : 0] s00_axi_wdata,
		input wire [3 : 0]	s00_axi_wstrb,
		input wire			s00_axi_wvalid,
		output wire			s00_axi_wready,
		output wire [1 : 0] s00_axi_bresp,
		output wire			s00_axi_bvalid,
		input wire			s00_axi_bready,
		input wire [3 : 0]	s00_axi_araddr,
		input wire [2 : 0]	s00_axi_arprot,
		input wire			s00_axi_arvalid,
		output wire			s00_axi_arready,
		output wire [31:0]	s00_axi_rdata,
		output wire [1 : 0] s00_axi_rresp,
		output wire			s00_axi_rvalid,
		input wire			s00_axi_rready,
		output				uart_tx,
		input				uart_rx,
		output				dataready,
		output				sendready,
		output				sendfull,
		output				recvempty
);

	/* uart and buffer */
	wire [31:0] ctl_state;

	reg [7:0]  send_buf_data;
	wire [7:0] send_buf_q;
	wire send_buf_full;
	wire send_buf_empty;
	wire [9:0] send_buf_used;
	reg send_buf_read;
	reg send_buf_write;
	
    uart_fifo_gen uart_send_buf(
		.clock(s00_axi_aclk),
		.rst(~s00_axi_aresetn),
		.data(send_buf_data),
		.rdreq(send_buf_read),
		.wrreq(send_buf_write),
		.empty(send_buf_empty),
		.full(send_buf_full),
		.q(send_buf_q),
		.usedw(send_buf_used));


	reg [7:0]  recv_buf_data;
	wire [7:0] recv_buf_q;
	wire recv_buf_empty;
	wire recv_buf_full;
	wire [9:0] recv_buf_used;
	reg recv_buf_read;
	reg recv_buf_write;
	
    uart_fifo_gen uart_recv_buf(
		.clock(s00_axi_aclk),
		.rst(~s00_axi_aresetn),
		.data(recv_buf_data),
		.rdreq(recv_buf_read),
		.wrreq(recv_buf_write),
		.empty(recv_buf_empty),
		.full(recv_buf_full),
		.q(recv_buf_q),
		.usedw(recv_buf_used));

	reg  send, recv;
	reg [7:0] senddata;
	wire [7:0] recvdata;
	wire uart_has_data;
	wire uart_can_send;
	reg [15:0] divsor;

	hdl4se_uart uart_u(
		.wClk(s00_axi_aclk), 
		.nwReset(s00_axi_aresetn),
		.divsor(divsor),
		//send
		.cansend(uart_can_send),
		.send(send),
		.senddata(senddata),
		.txd(uart_tx),
		//recv
		.hasdata(uart_has_data),
		.recvdata(recvdata),
		.recv(recv),
		.rxd(uart_rx)
	);

	assign sendfull = send_buf_full;
	assign recvempty = recv_buf_empty;
	assign dataready = uart_has_data;
	assign sendready = uart_can_send;

	reg [2:0] waitclk;
	always @(posedge s00_axi_aclk)	
	if (~s00_axi_aresetn) begin
		send <= 1'b0;
		recv <= 1'b0;
		senddata <= 0;
		recv_buf_write <= 1'b0;
		send_buf_read <= 1'b0;
		waitclk <= 0;
	end else begin
		send <= 1'b0;
		recv <= 1'b0;
		recv_buf_write <= 1'b0;
		send_buf_read <= 1'b0;
		if (waitclk == 0) begin
			if (uart_has_data && ~recv_buf_full) begin
				recv <= 1;
				recv_buf_data <= recvdata;
				recv_buf_write <= 1'b1;
				waitclk <= 4;
			end else if (uart_can_send && ~send_buf_empty) begin
				send_buf_read <= 1'b1;
				send <= 1;
				senddata <= send_buf_q;
				waitclk <= 4;
			end 
		end else begin
			waitclk <= waitclk - 1;
		end
	end

	assign ctl_state = {28'h0, send_buf_full, send_buf_empty, recv_buf_full, ~recv_buf_empty};

	/* axi bus */
	reg [1 : 0] 	axi_bresp;
	reg  			axi_bvalid;
	reg  			axi_arready;
	reg [31 : 0] 	axi_rdata;
	reg [1 : 0] 	axi_rresp;
	reg  			axi_rvalid;
	wire			slv_reg_rden;
	wire			slv_reg_wren;

	assign s00_axi_awready = 1'b1;
	assign s00_axi_wready = 1'b1;
	assign s00_axi_bresp	= axi_bresp;
	assign s00_axi_bvalid	= axi_bvalid;
	assign s00_axi_arready = axi_arready;
	assign s00_axi_rvalid = axi_rvalid;
	assign s00_axi_rdata = axi_rdata;
	assign s00_axi_rresp = axi_rresp;

	assign slv_reg_wren = s00_axi_wvalid && s00_axi_awvalid;

	always @( posedge s00_axi_aclk )
	begin
		if ( s00_axi_aresetn == 1'b0 ) begin
			divsor <= 50000000 / 115200;
			send_buf_write <= 0;
	    end else if (slv_reg_wren) begin
			send_buf_write <= 0;
			if ((s00_axi_awaddr & 4'hf) == 4'h4) begin
				send_buf_data <= s00_axi_wdata;
				send_buf_write <= ~recv_buf_full;
			end else if ((s00_axi_awaddr & 4'hf) == 4'hc) begin
				divsor <= s00_axi_wdata[15:0];
			end
		end else begin
			send_buf_write <= 0;
		end
	end    

	always @( posedge s00_axi_aclk )
	begin
		if ( s00_axi_aresetn == 1'b0 ) begin
			axi_bvalid  <= 0;
			axi_bresp   <= 2'b0;
	    end else if (slv_reg_wren) begin
			axi_bvalid <= 1'b1;
	        axi_bresp  <= 2'b0; // 'OKAY' response 
	    end else if (s00_axi_bready && axi_bvalid) begin
	        axi_bvalid <= 1'b0; 
	    end
	end   

	always @( posedge s00_axi_aclk )
	begin
		if ( s00_axi_aresetn == 1'b0 ) begin
			axi_rdata  <= 0;
			axi_rvalid <= 0;
			recv_buf_read <= 1'b0;
			axi_rresp <= 0;
	    end else if (s00_axi_arvalid) begin
			recv_buf_read <= 1'b0;
			axi_rvalid <= 0;
			if ((s00_axi_araddr & 4'hf) == 8) begin /* read state */
				axi_rdata <= ctl_state; 
				axi_rvalid <= 1;
			end else if ((s00_axi_araddr & 4'hf) == 0) begin/* read recv */
				axi_rdata <= {recv_buf_empty, 23'b0, recv_buf_q};
				recv_buf_read <= ~recv_buf_empty; 
				axi_rvalid <= 1;
			end
		end else begin
			recv_buf_read <= 0;
			axi_rvalid <= 0;
		end
	end    

endmodule