Releases for the NextJTAG tool
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NextJTAG is a standalone command line utility used for accessing Xilinx FPGAs over USB. It supports basic operations, such as checking the temperature and loading bitstreams. Platform and FPGA support are fairly limited, but more are coming soon. To gain access to all features, a license must be purchased. Check the releases to download the latest binaries.

Supported Features

  • Querying Device DNAs of attached FGPAs
  • Loading bitstreams in parallel (not persistent across power cycling)
  • Clearing the currently loaded bitstream
  • Reloading the bitstream from flash
  • Reading the min, max, and current temperature
  • Reading/writing SYSMON registers

Supported Xilinx FPGAs

  • XCVU9P (VCU1525, BCU1525, or BTU9P)
  • (More coming soon!)

Supported Platforms

  • Linux (x86-64)
  • Windows (x64)


Licensing is done per FPGA, and is tied to the FPGA's Device DNA (a unique identifier fused into the chip by the manufacturer). The majority of features require a license to use. The only feature that does not require a license is to list the Device DNAs of all FPGAs connected to the system.

Licenses are stored in a text file, with each line specifying the Device DNA and associated license separated by whitespace. Blank lines and lines starting with # are ignored. The license file is searched for in three places:

  1. If the NEXTJTAG_LICENSE environment variable is set, it will use the value as the (relative or absolute) path to the license file
  2. If the environment variable is not set, then it looks for nextjtag_license.txt in the current directory
  3. If that file does not exist, it looks for nextjtag_license.txt in the directory the NextJTAG tool is located in

Licenses must be purchased from Next Design Solutions directly or through an authorized third party vendor (see purchasing options). Licenses are valid indefinitely, but will only work with the same major version of NextJTAG. For example, a 1.x license will work with versions 1.0 and 1.1, but will not not with version 2.0. In general, bug fixes and basic new features will not result in a major version bump.

Purchasing options

  • (Paypal, Credit Card, or various crypto currencies)
  • Contact turekaj#2845 on discord (Ethereum only)

Permissions (Linux only)

NextJTAG needs access to the FTDI chip on the FPGA over USB in order to work, which requires special permissions on Linux platforms. There are two options:

  1. Run as root user (not ideal, but convenient)
  2. Install udev rules to allow non-root users access to read and write to USB FTDI devices (best practice)

To do option 2, simply copy the .rules files from the release (located in <release>/lib/udev/rules.d) into the /etc/udev/rules.d directory on your system. However, the rule will only apply to new USB connections. If you already have a FPGA connected over USB, you can manually trigger the rule by running udevadm trigger --action=add as root.

Driver Install (Windows only)

NextJTAG requires an open source driver, instead of the proprietary FTDI driver that Vivado and some miners use. In order to use NextJTAG, windows needs to forced to use the open source driver on the FTDI JTAG interface (Interface 0) of the FPGA cards.

  1. (optional) Install the proprietary driver. This will create a clean slate, and will use the proprietary driver as default the for all interfaces for the FTDI chip. If you are already using Vivado, this is probably not necessary
  2. Download the zadig tool and run it as administrator. This is a convenient tool to for installing drivers compatible with libusb
  3. In Zadig, select Options > Show all devices, and then use the dropdown to select Interface 0 for one of your FPGA cards. On the line below the dropdown, select libusbK and then hit the Replace Driver button. Repeat for Interface 0 for all of your FPGA cards. Do not replace the driver for the other interfaces, since some miners require the proprietary driver for those to work.

alt text

The changes made by Zadig will be persistent, even after reboots. To remove the open source driver, just install the proprietary drive again from step 1. You will need to do this in order to use Vivado again after running these steps


Query Device DNAs from all attached devices (no license required):

$ nextjtag
List of available devices:
  0: Xilinx VCU1525 Dev Kit (DNA = 400200000117ab282d410505)

Read the temperature from device 0:

$ nextjtag -d0 -t
[2018-11-12 03:32:50] Device 0: Temperature: 43.5624°C (min), 58.4837°C (current), 71.4155°C (max)

Program bitstream into all FPGAs in parallel:

$ nextjtag -a -m -b vcu1525_keccak_21_600.bit
[2018-11-11 21:38:34] Device 0: Programming bitstream: STARTING...
[2018-11-11 21:38:34] Device 1: Programming bitstream: STARTING...
[2018-11-11 21:38:34] Device 2: Programming bitstream: STARTING...
[2018-11-11 21:38:34] Device 3: Programming bitstream: STARTING...
[2018-11-11 21:39:21] Device 1: Programming bitstream: SUCCESS
[2018-11-11 21:39:21] Device 0: Programming bitstream: SUCCESS
[2018-11-11 21:39:21] Device 2: Programming bitstream: SUCCESS
[2018-11-11 21:39:22] Device 3: Programming bitstream: SUCCESS


How to fix some common problems.

No devices avaiable

$ nextjtag
List of available devices:
  (No devices found)

Check that your FPGAs are plugged in. On Linux, you can do lsusb and search for FT4232H or "Future Technology Devices International" (FTDI). On Windows, check device manager, and make sure you have gone through the driver install

Unable to open device (no device name)

$ nextjtag
List of available devices:
  0:  (Unable to open device)

On Linux, this is probably a permission problem. Try running as root or installing udev rules.

On Windows, this might be a driver issue. Sometimes a reboot will help.

Unable to open device (with device name)

$ nextjtag
List of available devices:
  0: Xilinx VCU1525 Dev Kit (Unable to open device)

The device is probably already open by another process. Check for other instances of NextJTAG that are running. Also check if Vivado is running, and if so, make sure it isn't connected to the FPGA. If that doesn't work, you can try rebooting.

Unable to initialize device

$ nextjtag
List of available devices:
  0: Xilinx VCU1525 Dev Kit (Unable to initialize FPGA)

This means that it was able to open the device, but it received something unexpected from the FTDI chip. For example, this can happen if you use NextJTAG with a non-supported FPGA. It is also possible that the FTDI chip is in a bad state, but that is pretty rare. You can try power cycling the card to see if it helps.

Bogus min/max temperatures

$ nextjtag -a -t
[2018-11-14 00:48:23] Device 0: Temperature: 228.5866°C (min), 53.5099°C (current), -280.2300°C (max)

This is a known issue with certain hardware/bitstream configurations, and something we can hopefully provide a workaround for in the future.

Weird characters being printed out for temperature command

This is probably an issue with your shell not rendering the degree symbol, which requires UTF-8 encoding.

On Windows, run chcp 65001 in the command prompt or [Console]::OutputEncoding = [System.Text.Encoding]::UTF8 in powershell.

On Linux, it depends on your terminal program.