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.