Connections to a target GDB stub using Virtual Ethernet/TTY mode (Target-GDB-Virtual Ethernet)

If your target application requires TCP/IP communication with the debug host, you can connect to the target using Virtual Ethernet/TTY mode. Connections of this type are referred to as Target-GDB-Virtual Ethernet connections. This method is an extension to that used for connections to a target running an application with a GDB stub. The following figure shows an example:

Figure 55. Target-GDB-Virtual Ethernet connections

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In this method, debug hardware provides a network bridging feature to targets, and enables a target with only a JTAG connection to debug hardware to have access to the same network resources available to debug hardware. This works by intercepting IP packets on the network and examining them, and those packets that are addressed to the target are then sent over DCC alongside the normal GDB protocol. A driver is required on the target to interface the DCC channel to the protocol stack of the target, making the bridged network connection appear as an Ethernet device on the target. IP is the only network layer protocol supported.


To reduce the load on the DCC and JTAG connection, broadcast packets are not sent to the target.

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Use the Target-GDB-Virtual Ethernet connection method to communicate with a standalone application that has a TCP/IP stack. For example, an application might provide a web server that serves web pages to the host.


To use the Target-GDB-Virtual Ethernet connection method:

  • It is recommended that you compile the DCC driver and GDB stub into your target application using a GNU toolchain for ARM® architectures. The DCC driver is available as a Linux OS download from the ARM products and solutions website.


    On the GDB connection to the target, you must enable DCC and Virtual Ethernet/TTY mode before starting the processor.

  • The target application must be running a TCP/IP stack.

  • debug hardware acts as a network bridge between the target processor and the host PC using a virtual Ethernet link. The target must have its own IP address that is either fixed or obtained from a DHCP server, and that appears on the virtual Ethernet as an independent host.

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