
It’s finally here! The Bus Blaster v2 JTAG debugger is now in stock and shipping at Seeed Studio.
Read the full hardware design article
There’s a ton of JTAG debuggers out there, what makes the Bus Blaster v2 so special? V2 has a reprogrammable logic chip (CPLD) that sits between the FT2232H USB chip and the JTAG output header. The pinout and buffer logic can be updated on the fly.
Have an app that’s only compatible with a simple JTAGkey-type debugger? Program the JTAGkey buffer logic. Want to try the proposed Serial Wide Debug support in OpenOCD and urJTAG? Program the KT-link-type buffer. If a new programmer type becomes popular, we can release new buffer logic for it too.
The design is so flexible and fun, we can’t believe it wasn’t the standard FT2232 JTAG debugger design already. It’s a JTAG debugger that can clone many other debuggers, and it’s an all-in-one CPLD development board. And it’s cheap!
A patch that supports v2’s self-programming feature was accepted by urJTAG and will be included in the next release. Until then, we have a patched nightly compile that can be used to switch buffer logic.
At a glance:
- Based on FT2232H with high-speed USB 2.0
- Buffered interface works with 3.3volt to 1.2volt targets
- Reprogrammable buffer is compatible with multiple debugger types
- Compatible with ‘jtagkey’, ‘KT-link’ programmer settings in OpenOCD, urJTAG, and more
- Should support Serial Wire Debug when available
- Mini-CPLD development board: self programmable, extra CPLD pins to header
- Open source (CC-BY-SA)

The Bus Blaster is used to program and debug devices with a JTAG interface like ARM processors, CPLDs, flash memory, and more.
A FT2232H USB chip gives us two high-speed JTAG interfaces. The 16 pins of the primary interface are connected to a CoolRunner-II CPLD. The CPLD is a programmable buffer that translates between the FT2232H at 3.3volts, and a 1.2volt to 3.3volt target.
Many JTAG debuggers use the FT2232 chips, but they have slightly different buffers. The CPLD can be programmed to imitate many of them, so it works out of the box with our favorite open source debugging apps. Updates are done over USB using the second JTAG interface on the FT2232H.
This project was developed in a public forum, and progress was documented on a wiki.

Resources
You can get a Bus Blaster v2 for $34.95 only at Seeed Studio.