www.waveshare.com
Hello,
Ok, given that you are new in this field, your best approach would be to split up the "todo"s.
What if they don't know anything about logic design and hardware?
If you want to do it very fast you can use Instant SoC.
/*
* Milkymist VJ SoC
* Copyright (C) 2007, 2008, 2009, 2010 Sebastien Bourdeauducq
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, version 3 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
module uart #(
parameter csr_addr = 4'h0,
parameter clk_freq = 100000000,
parameter baud = 115200
) (
input sys_clk,
input sys_rst,
input [13:0] csr_a,
input csr_we,
input [31:0] csr_di,
output reg [31:0] csr_do,
output rx_irq,
output tx_irq,
input uart_rx,
output uart_tx
);
reg [15:0] divisor;
wire [7:0] rx_data;
wire [7:0] tx_data;
wire tx_wr;
reg thru;
wire uart_tx_transceiver;
uart_transceiver transceiver(
.sys_clk(sys_clk),
.sys_rst(sys_rst),
.uart_rx(uart_rx),
.uart_tx(uart_tx_transceiver),
.divisor(divisor),
.rx_data(rx_data),
.rx_done(rx_irq),
.tx_data(tx_data),
.tx_wr(tx_wr),
.tx_done(tx_irq)
);
assign uart_tx = thru ? uart_rx : uart_tx_transceiver;
/* CSR interface */
wire csr_selected = csr_a[13:10] == csr_addr;
assign tx_data = csr_di[7:0];
assign tx_wr = csr_selected & csr_we & (csr_a[1:0] == 2'b00);
parameter default_divisor = clk_freq/baud/16;
always @(posedge sys_clk) begin
if(sys_rst) begin
divisor <= default_divisor;
csr_do <= 32'd0;
end else begin
csr_do <= 32'd0;
if(csr_selected) begin
case(csr_a[1:0])
2'b00: csr_do <= rx_data;
2'b01: csr_do <= divisor;
2'b10: csr_do <= thru;
endcase
if(csr_we) begin
case(csr_a[1:0])
2'b00:; /* handled by transceiver */
2'b01: divisor <= csr_di[15:0];
2'b10: thru <= csr_di[0];
endcase
end
end
end
end
endmodule/*
* Milkymist VJ SoC
* Copyright (C) 2007, 2008, 2009, 2010 Sebastien Bourdeauducq
* Copyright (C) 2007 Das Labor
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, version 3 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
module uart_transceiver(
input sys_rst,
input sys_clk,
input uart_rx,
output reg uart_tx,
input [15:0] divisor,
output reg [7:0] rx_data,
output reg rx_done,
input [7:0] tx_data,
input tx_wr,
output reg tx_done
);
//-----------------------------------------------------------------
// enable16 generator
//-----------------------------------------------------------------
reg [15:0] enable16_counter;
wire enable16;
assign enable16 = (enable16_counter == 16'd0);
always @(posedge sys_clk) begin
if(sys_rst)
enable16_counter <= divisor - 16'b1;
else begin
enable16_counter <= enable16_counter - 16'd1;
if(enable16)
enable16_counter <= divisor - 16'b1;
end
end
//-----------------------------------------------------------------
// Synchronize uart_rx
//-----------------------------------------------------------------
reg uart_rx1;
reg uart_rx2;
always @(posedge sys_clk) begin
uart_rx1 <= uart_rx;
uart_rx2 <= uart_rx1;
end
//-----------------------------------------------------------------
// UART RX Logic
//-----------------------------------------------------------------
reg rx_busy;
reg [3:0] rx_count16;
reg [3:0] rx_bitcount;
reg [7:0] rx_reg;
always @(posedge sys_clk) begin
if(sys_rst) begin
rx_done <= 1'b0;
rx_busy <= 1'b0;
rx_count16 <= 4'd0;
rx_bitcount <= 4'd0;
end else begin
rx_done <= 1'b0;
if(enable16) begin
if(~rx_busy) begin // look for start bit
if(~uart_rx2) begin // start bit found
rx_busy <= 1'b1;
rx_count16 <= 4'd7;
rx_bitcount <= 4'd0;
end
end else begin
rx_count16 <= rx_count16 + 4'd1;
if(rx_count16 == 4'd0) begin // sample
rx_bitcount <= rx_bitcount + 4'd1;
if(rx_bitcount == 4'd0) begin // verify startbit
if(uart_rx2)
rx_busy <= 1'b0;
end else if(rx_bitcount == 4'd9) begin
rx_busy <= 1'b0;
if(uart_rx2) begin // stop bit ok
rx_data <= rx_reg;
rx_done <= 1'b1;
end // ignore RX error
end else
rx_reg <= {uart_rx2, rx_reg[7:1]};
end
end
end
end
end
//-----------------------------------------------------------------
// UART TX Logic
//-----------------------------------------------------------------
reg tx_busy;
reg [3:0] tx_bitcount;
reg [3:0] tx_count16;
reg [7:0] tx_reg;
always @(posedge sys_clk) begin
if(sys_rst) begin
tx_done <= 1'b0;
tx_busy <= 1'b0;
uart_tx <= 1'b1;
end else begin
tx_done <= 1'b0;
if(tx_wr) begin
tx_reg <= tx_data;
tx_bitcount <= 4'd0;
tx_count16 <= 4'd1;
tx_busy <= 1'b1;
uart_tx <= 1'b0;
`ifdef SIMULATION
$display("UART: %c", tx_data);
`endif
end else if(enable16 && tx_busy) begin
tx_count16 <= tx_count16 + 4'd1;
if(tx_count16 == 4'd0) begin
tx_bitcount <= tx_bitcount + 4'd1;
if(tx_bitcount == 4'd8) begin
uart_tx <= 1'b1;
end else if(tx_bitcount == 4'd9) begin
uart_tx <= 1'b1;
tx_busy <= 1'b0;
tx_done <= 1'b1;
end else begin
uart_tx <= tx_reg[0];
tx_reg <= {1'b0, tx_reg[7:1]};
end
end
end
end
end
endmodule