Github: https://github.com/ultraembedded/core_usb_uart
This component is a simple USB Peripheral Interface (Device) implementation which enumerates as either a high-speed (480Mbit/s) or full-speed (12Mbit/s) CDC-ACM device.
This IP acts as a USB to serial port (UART) converter which can be used to add a UART to a FPGA which has a ULPI interface.
- High or Full speed USB CDC device.
- Enumeration in hardware - no SW intervention required.
- ULPI interface (suitable for connection to a ULPI PHY - e.g. Microchip USB3300)
- Fixed baud rate (param) Rx, Tx pins.
module usb_serial
//-----------------------------------------------------------------
// Params
//-----------------------------------------------------------------
#(
parameter BAUDRATE = 1000000
)
//-----------------------------------------------------------------
// Ports
//-----------------------------------------------------------------
(
output uart_rx_o
, input uart_tx_i
// ULPI Interface
, output ulpi_reset_o
, inout [7:0] ulpi_data_io
, output ulpi_stp_o
, input ulpi_nxt_i
, input ulpi_dir_i
, input ulpi_clk60_i
);
// USB clock / reset
wire usb_clk_w;
wire usb_rst_w;
wire clk_bufg_w;
IBUF u_ibuf ( .I(ulpi_clk60_i), .O(clk_bufg_w) );
BUFG u_bufg ( .I(clk_bufg_w), .O(usb_clk_w) );
reg [3:0] count_q = 4'b0;
reg rst_q = 1'b1;
always @(posedge usb_clk_w)
if (count_q != 4'hF)
count_q <= count_q + 4'd1;
else
rst_q <= 1'b0;
assign usb_rst_w = rst_q;
// ULPI Buffers
wire [7:0] ulpi_out_w;
wire [7:0] ulpi_in_w;
wire ulpi_stp_w;
genvar i;
generate
for (i=0; i < 8; i=i+1)
begin: gen_buf
IOBUF
#(
.DRIVE(12),
.IOSTANDARD("DEFAULT"),
.SLEW("FAST")
)
IOBUF_inst
(
.T(ulpi_dir_i),
.I(ulpi_out_w[i]),
.O(ulpi_in_w[i]),
.IO(ulpi_data_io[i])
);
end
endgenerate
OBUF
#(
.DRIVE(12),
.IOSTANDARD("DEFAULT"),
.SLEW("FAST")
)
OBUF_stp
(
.I(ulpi_stp_w),
.O(ulpi_stp_o)
);
// USB Core
usb_cdc_top
#( .BAUDRATE(BAUDRATE) )
u_usb
(
.clk_i(usb_clk_w)
,.rst_i(usb_rst_w)
// ULPI
,.ulpi_data_out_i(ulpi_in_w)
,.ulpi_dir_i(ulpi_dir_i)
,.ulpi_nxt_i(ulpi_nxt_i)
,.ulpi_data_in_o(ulpi_out_w)
,.ulpi_stp_o(ulpi_stp_w)
,.tx_i(uart_tx_i)
,.rx_o(uart_rx_o)
);
assign ulpi_reset_o = 1'b0;
endmodule
- Really basic USB-CDC class device implementation, will ignore encap, line state and line coding change requests!
- USB suspend/resume will not work correctly.
Verified under simulation then tested on FPGA against Linux, Windows and MAC OS-X.