wiki:howto/USB_UART

Version 1 (modified by murphpo, 12 years ago) (diff)

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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.

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 PuTTY.

Configuring PuTTY

PuTTY is very flexible. We recommend adopting the following settings.

  1. Launch PuTTY; you should see this window:

  1. Apply these settings:
    • Session:
      • Serial line = see below
      • Connection type = Serial
      • Speed = 57600
    • Terminal:
      • Enable "Implicit CR in every LF" and "Implicit LF in every CR"
    • Connection->Serial:
      • Speed = 57600
      • Data bits = 8
      • Stop bits = 1
      • Parity = None
      • Flow control = XON/XOFF
  2. Go back to the Session settings pane
  3. 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')
  2. Expand Ports (COM & LPT)
  3. Look for the port named "USB Serial Port" and note the COM number assigned. In the screenshot below, the USB-UART interface is COM14.

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

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