Providing IP connectivity for the FPGA board

If the FPGA board (e.g., RFSoC or PYNQ) is connected directly to the host, it may not have Internet access. However, the board can obtain IP access through the IP access on your host machine.
You’ll bridge your Windows Wi-Fi (or other internet-connected interface) to the Ethernet interface connected to the FPGA board. Thoe host will act as a NAT gateway.

Setting a Windows Host

  • Open Control Panel->Network and Internet->Network Connections
  • Identify the interface associated with the FPGA board. Typically, this is Ethernet 2 or Ethernet 4.
    • You can also see which one from running the powershell command ipconfig and identifying the interface on the subnet.
    • For example, for the PYNQ-Z2 board, the IP address will be on the 192.168.2.xx subnet
  • Still in the Network Connections panel, right click on whichever interface you are using for connectivity to the Internet and select Properties.
    • For example, this could be Wi-Fi.
  • Check: ✅ “Allow other network users to connect through this computer’s Internet connection”
  • In the dropdown, select the Ethernet interface connected to the PYNQ-Z2 or the FPGA board
  • Click OK
  • Windows will automatically assign a static IP (usually 192.168.137.1) to the Ethernet interface. You can confirm the IP address with a command like: 
       Get-NetIPAddress | Where-Object {$_.InterfaceAlias -like "Ethernet*"}

    This will return something like:

      IPAddress         : 192.168.137.1
  InterfaceIndex    : 43
  InterfaceAlias    : Ethernet 2
  AddressFamily     : IPv4

    from which we can see the IP address of the Ethernet interface. For the instructions below, we will call this address <host_ip_addr>

  • You may lose connectivity to the FPGA board since Windows will assign it a new IP address. To find the new address, type: 
     arp -a

    Look for IP addresses in the same subnet as the IP address of the Ethernet interface, in our example, 192.168.137.x. Try pinging those IPs to see which one has connectivity. For example, it could be 192.168.137.139

  • There is a possibility that you do not see any IP addresses when you run arp -a. In this case, you will need to find the IP address as follows:
    • Log into via the USB serial interface (see below)
    • Run 
         ip addr show eth0
    • Look for an IP address in the same subnet as the <host_ip_addr>. For example, in our example, this could be 192.168.137.x.
  • You should now be able to reconnect the browser to the http://192.168.137.139:9090/lab or whatever the IP address of the Pynq board is
  • For Windows host, the FPGA board should automatically acquire a gateway and DNS server. You can test as follows:
    • Open a terminal on the FPGA board (e.g., via Jupyter lab)
    • Try ping 8.8.8.8 meaning the gateway is set up
    • Try ping www.google.com meaning the DNS is working

Setting Up a Linux Host

  • On the Linux host machine, run 
    ip link show

    This will list your IP interfaces.

  • Try to identify the Internet-facing interface. On the machine in NYU, it is enp0d31f6 since it is state UP. Sometimes, it may be eth0 or wlan0.
  • Then in the terminal of the host machine run 
      sudo sysctl -w net.ipv4.ip_forward=1
  sudo iptables -t nat -A POSTROUTING -o enp0d31f6 -j MASQUERADE
  • Get the name of the interface on the PYNQ board connected to the host:
    • On the PYNQ board terminal, ifconfig.
    • If you are connected via USB, the interface should have a name like usb0 with an IP address like 192.168.3.1.
    • In the instructions below, we will call this interface name pynq_if_name.
  • Get the IP address of the host machine interface to the board:
    • In the terminal of the host machine, type ifconfig.
    • This will list a number of interfaces. Find the interface likely associated with connection to the board. It will likely be on the same subnet as the interface on the PYNQ.
    • On the NYU lab machine, the IP address is 192.168.3.102
    • Test that this is the correct IP address by trying to ping that IP address from the board.
  • Open a terminal on the FPGA board (e.g., PYNQ-Z2). You can do this from Jupyter Lab.
  • On the PYNQ terminal 
      sudo route add default gw <host_ip_addr> <pynq_if_name>

    So, in our example with the Windows host:

      sudo route add default gw 192.168.137.1 eth0
  • Finally, you may need to add a DNS server. you can add Google’s DNS server: 
      sudo bash -c 'echo "nameserver 8.8.8.8" > /etc/resolv.conf'
  • Test ping www.google.com to make sure you have connectivity.

Connecting via the USB port

When all connectivity is lost, your lifeline to the FPGA board may be the serial USB connection. This USB option is available on the Pynq-Z2 and the RFSoC 2x2. To connect to the board via serial connection:

  • Find the port (e.g., COM4) corresponding to the USB connection to the FPGA board
    • On Windows: Go to Device Manager->Ports.
      • You should see something like USB Serial Port (COM4), USB‑UART Bridge (COM3) or Silicon Labs CP210x USB to UART Bridge (COMx)
      • The number COMx is the number you want.
    • On Linux:
      • Run 
          dmesg | grep ttyUSB

        or

          ls /dev/ttyUSB*
      • You’ll typically see /dev/ttyUSB0 (sometimes /dev/ttyUSB1 if multiple devices are connected).
      • That device path is what you’ll use in your serial terminal.
  • Open a serial terminal application.
    • On Windows, you can install Putty
    • On Linux, you can use minicom, screen, or picocom.
      • Example with screen: 
          screen /dev/ttyUSB0 115200
  • Open a session. Select Serial session and set Speed (baud) to 115200.
    • Note that if you do not set the baud rate correctly, the connection witll not work. This baud rate seems to work with Pynq-Z2. Other FPGA boards may have other baud rates. Sorry
  • You should be able to log in. Default credentials for Pynq boards:
    • Username: xilinx
    • Password: xilinx.
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