On-chip debug (OCD) interfaces can provide chip-level control of a target device and are a primary vector used by engineers, researchers, and hackers to extract program code or data, modify memory contents, or affect device operation on-the-fly. Depending on the complexity of the target device, manually locating available OCD interfaces can be a difficult and time consuming task, sometimes requiring physical destruction or modification of the device.

JTAGulator is an open source hardware tool that assists in identifying OCD interfaces from test points, vias, component pads, or connectors on a target device.

Parallax, Inc. was the official hardware manufacturer of the JTAGulator. Production has ended as of April 28, 2023. Support will continue to be provided only for genuine JTAGulators, which are hot pink in color and contain verifiable serial numbers.

This design is distributed under a Creative Commons Attribution-3.0 United States license. The JTAGulator name and logo are registered trademarks of Grand Idea Studio, Inc. The trademarks may not be used on derived works without permission.

  • Detection of JTAG/IEEE 1149.1, ARM SWD, and UART/asynchronous serial
  • Direct connection to sigrok and OpenOCD
  • 24 channels with input protection circuitry
  • Adjustable target I/O voltage for level translation: 1.4V to 3.3V
  • USB interface for menu-based control from host computer
Additional Resources:
Raspberry Pi Zero W:

Environment to demonstrate JTAG, UART, and logic analyzer functionality.

Acrylic Case:
Sparkle Add-On Board:

Provides neon pink underglow for maximum aesthetics. Connects to the JTAGulator with pogo pins. LEDs will turn on when the target voltage (VADJ) is set.