The Bus Blaster v1 is a prototype board (from Dangerous Prototypes) that allows to access the JTAG connection of integrated circuits through USB, using the FTDI FT2232H chip for the conversion. The prototype is on sale at around 35$ as they say on their page, but keep in mind that it is still a prototype, so I would advise buying it if you know how to solder and desolder, in case an error slipped in the PCB design and you need to fix it without re-buying the board. Still, the price is interesting since there are some commercial products in the range of 100$. Moreover the board design is open source, which is a nice addition and offers a starting point for hobbyists to begin developing their own debugging board or integrate the design into their own bigger board.
Connecting the Bus Blaster with the JTAG port of a supported microcontroller allows to debug the software running on it using GDB. This is possible also thanks to software like OpenOCD that translates debugging commands to JTAG sequences to send through the FT2232H to the microcontroller. It’s also possible to have more devices connected to the JTAG interface in daisy chain; this is common in board designs that mount more than one complex integrated circuits (for example a SoC and an FPGA).
Example of a multi-chip JTAG connection, that allows debugging through the Bus Blaster.
See also:
- JTAG tutorial at fpga4fun
- List of debugging hardware supported by OpenOCD
- List of CPU cores supported by OpenOCD
Entries
dinsh
2011/03/05
Does it support xilinx JTAG usb cable? Thx!
Balau
2011/03/05
You mean something like this?
You want to program an FPGA using the Bus Blaster JTAG debugger instead of the xilinx JTAG usb cable, is that correct?
If this is the case, I think it can be done only if the Xilinx tools support the FTDI chip. I don’t know if they do, but I think that, since Xilinx sells the cables, they have little incentive to support them.
dinsh
2011/03/07
Thx for your answer. I have a xilinx JTAG usb cable. And now I want to use it to debug Openrisc which is proved to be compatible to GDB and OpenOCD. I cant find the xilinx cable in your list of debugging hardware supported by OpenOCD.
So I want to ack does the xilinx JTAG usb cable support OpenOCD? Thx!
dinsh
2011/03/07
The cable I have is like you point —http://www.xilinx.com/products/devkits/HW-USB-II-G.htm
Balau
2011/03/07
I’m sorry but OpenOCD does not support the Xilinx JTAG USB (DLC10) cable; the closest to it is the parallel port version (DLC5).
If you want to debug the OpenRISC you need to buy another debugger such as the Bus Blaster or the OrSoc debugger which is based on the FT2232D chip and has a 10-pin JTAG connector.
dinsh
2011/03/08
Thanks a lot. Now I start to try OrSoc debugger. It’s a long way for me… Thanks!