Chipmunk JTAG – Inexpensive JTAG adapter for hackers

We designed a CPLD breakout board many months ago based on Ian Lesnet’s CPLD breakout design. Like many other CPLD/FPGA platforms, you need a JTAG programmer/adapter to program the onboard CPLD. Many of the JTAG programmers out there that supports Xilinx CPLDs seems to cost a couple hundred dollars at a minimum. One of the cheapest JTAG adapter you can find would be Ian’s Bus Pirate (Approximately $30, We used a bus Pirate to test the CPLD prototype board ourselves). Bus Pirate is a great value for money since it supports a multitude of other protocols besides JTAG.

We gave away some CPLD breakout PCBs a few months back and some readers assembled and tested them successful. There were many people asking if they could buy fully assembled board through our store. It was a great idea to sell the boards but we thought it was pointless to sell the CPLD breakout unless we offer an inexpensive JTAG hardware that people can buy along with the board. Our thoughts were along the lines of “No Bells and Whistles” generic JTAG hardware that can be used with a small Windows/Linux application utility to download SVF/XSVF stream to the CPLD. A flexible SVF/XSVF implementation would allow the hardware to be used with many different CPLDs and FPGAs. here are some of the goals we want to achieve with Chipmunk JTAG adapter design.

Inexpensive hardware (less than $10)
Flexibility in terms of different JTAG device support
A serial (USB CDC) console based command line interface for easy hacking
A packet based interface for better speed (Speed is not a high priority item at least for now)
Multiple feature/personality support by switching firmware (Using bootloader)
Open design
So far we made some progress in designing the hardware and planning the features. We will share more details in future posts, stay tuned!

Cipmunk JTAG update 06/16/2013

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