Xilinx Virtual Cable (XVC) is a TCP/IP-based protocol that acts like a JTAG cable and provides a means to access and debug your FPGA or SoC design without using a physical cable. A full description of Xilinx Virtual Cable in action is provided in the XAPP1252 application note.

Xvcpi implements an XVC server to allow a Xilinx FPGA or SOC to be controlled remotely by Xilinx Vivado using the Xilinx Virtual Cable protocol. Xvcpi uses TCP port 2542.

The xvcpi server runs on a Raspberry Pi which is connected, using JTAG, to the target device. Xvcpi bitbangs the JTAG control signals on the Pi pins. The bitbanging code was originally extracted from OpenOCD.

Note: The Raspberry Pi is a 3.3V device. Ensure that the target device and the Pi are electrically compatible before connecting. 100 Ohm resistors may be placed inline on all of the JTAG signals to provide a degree of electrical isolation.

JTAG uses 4 signals, TMS, TDI, TDO and, TCK. From the Raspberry Pi perspective, TMS, TDI and TCK are outputs, and TDO is an input. The default pin mappings for the Raspberry Pi header are:

TMS=25, TDI=10, TCK=11, TDO=9

The pin mappings can be changed by optional flags of xvcpi: -c(for TCK), -m(for TMS), -i(for TDI), -o(for TDO).

./xvcpi -c 22 -m 23 -i 24 -o 25

Above command changes the pin mappings to:

TMS=23, TDI=24, TCK=22, TDO=25

In addition a ground connection is required. Pin 6 of the Model B+ 40-Pin header is a conveniently placed GND.

Note that XVC does not provide control of either SRST or TRST and xvcpi does not support a RST signal.

Start xvcpi on the Raspberry Pi. An optional -v flag can be used for verbose output.

Vivado connects to xvcpi via an intermediate software server called hw_server. To allow Vivado "autodiscovery" of xvcpi via hw_server run:

hw_server -e 'set auto-open-servers xilinx-xvc:<xvcpi-server>:2542'

Alternatively, the following tcl commands can be used in the Vivado Tcl console to initiate a connection.

connect_hw_server
open_hw_target -xvc_url <xvcpi-server>:2542

Full instructions can be found in ProdDoc_XVC_2014 3.

The initial purpose of xvcpi was to provide a simple means of programming the Snickerdoodle.

This work, "xvcpi.c", is a derivative of "xvcServer.c" (https://github.com/Xilinx/XilinxVirtualCable)

"xvcServer.c" is licensed under CC0 1.0 Universal (http://creativecommons.org/publicdomain/zero/1.0/) by Avnet and is used by Xilinx for XAPP1251.

"xvcServer.c", is a derivative of "xvcd.c" (https://github.com/tmbinc/xvcd) by tmbinc, used under CC0 1.0 Universal (http://creativecommons.org/publicdomain/zero/1.0/).

Portions of "xvcpi.c" are derived from OpenOCD (http://openocd.org)

"xvcpi.c" is licensed under CC0 1.0 Universal (http://creativecommons.org/publicdomain/zero/1.0/) by Derek Mulcahy.