= Using the USB-UART Interface on WARP Hardware =
WARP hardware uses a USB-UART transceiver to interface between a PC-based terminal and a UART in the FPGA. The primary use of this interface is to interact with STDIN/STDOUT of embedded processors. All WARP reference designs connect STDIN/STDOUT to a UART.

The WARP FPGA Board v2 (Virtex-4 FPGA) provides both a USB-UART and a RS-232/DB9 UART. The instructions below apply only to the USB-UART.

The basic steps to using the USB-UART are:
 * Install the FTDI drivers
 * Install a terminal application
 * Connect to the USB-UART

= Drivers =
Both WARP v2 and v3 use USB-UART transceivers from FTDI. Although the boards use different FTDI devices, they use the same driver.

Download the drivers for your OS from the FTDI drivers page: [http://www.ftdichip.com/Drivers/VCP.htm http://www.ftdichip.com/Drivers/VCP.htm].

Be sure you install the '''VCP''' driver (Virtual COM Port). Do not install the D2XX drivers.

= Terminal =
There are many options for terminal applications.

For Windows, we recommend [http://www.chiark.greenend.org.uk/~sgtatham/putty/ PuTTY].

== Configuring PuTTY ==
PuTTY is very flexible. We recommend adopting the following settings.
 1. Launch PuTTY; you should see this window:

[[Image(putty_config.png,nolink)]]

 2. Apply these settings:
  * Session:
   * Serial line = ''see below''
   * Connection type = Serial
   * Speed:
     * WARP v2
       * WARPLab v6/v7:  Speed = 57600
     * WARP v3
       * WARPLab v6:  Speed = 57600
       * WARPLab v7:  Speed = 115200
  * Terminal:
   * Enable "Implicit CR in every LF" and "Implicit LF in every CR"
  * Connection->Serial:
   * WARP v2
     * WARPLab v6/v7:  Speed = 57600
   * WARP v3
     * WARPLab v6:  Speed = 57600
     * WARPLab v7:  Speed = 115200
   * Data bits = 8
   * Stop bits = 1
   * Parity = None
   * Flow control = XON/XOFF
 1. Go back to the Session settings pane
 1. Click Default Settings, then click Save
   * This will save your defaults and apply them every time PuTTY launches





== Finding the COM Port ==
When you connect the USB-UART interface to your PC, your OS will emulate a serial port connection. The name of this connection is not fixed.

In Windows the connection is named COMX, for some integer X. In our experience the FTDI drivers assign a new COM port number to each unique board.

To find the current COM port number:
 1. Open Device Manager (run 'devmgmt.msc')
 1. Expand "Ports (COM & LPT)"
 1. Look for the port named "USB Serial Port" and note the COM number assigned. In the screenshot below, the USB-UART interface is COM14.

[[Image(dev_manager.png,nolink)]]

 1. Use this port name in the "Serial line" field when opening PuTTY.

= Testing the Connection =
To test the connection, program your FPGA with any design which uses the USB-UART for STDOUT.

On WARP v2, be sure your software project uses the USB-UART for STDOUT (and not the RS-232/DB9 UART). This is configured in the BSP settings in SDK.

On WARP v3, all projects use the USB-UART for STDOUT. You can download any reference project to test the USB-UART.