We’ve just completed verification of the Bus Blaster v2 JTAG debugger. V2 is much more flexible than v1, and uses a programmable logic chip (CPLD) for the buffer. The logic chips in v1 were expensive to source and place, but v2 uses a $1 CPLD with a bunch less pins to solder and inspect. Bus Blaster v1 will be available soon in limited production, then we’ll switch to v2.
The CPLD can be programmed to resemble just about any existing FT2232-based JTAG debugger. Proprietary software needs some funky connection to a JTAG device? No problem, just implement it in the CPLD.
Our first CPLD implementation is a clone of the Amontec JTAGkey. This is a common debugger that’s copied in a lot of projects, like OpenMoko. Eventually we’d like to have a full library of different interface clones that can be used with Bus Blaster v2.
We used Bus Blaster v1 to program the Bus Blaster v2 CPLD, though the goal is to make v2 self-programming. The CPLD is connected to the secondary JTAG interface on the FT2232 so it can be done, in theory. The problem is that our loader software doesn’t support the B interface yet. Robots and Tornado are currently looking into it.
We’re going to start the Bus Blaster v2 production process. We hope to have the ability to upgrade the CPLD without an external programmer before launch, but if not that’s ok. The current interface is sufficient for most uses, and it clones the Bus Blaster v1 connections. The great thing about open source is that anyone can contribute these features later, we don’t have to have a complete project from the beginning.
You might notice the fly wire from C1 to C19 – this happened because the supply pin wasn’t fully connected in the Eagle schematic. Simple problem to fix in the v2a production version.