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The Universal USB to Serial breakout board is designed to allow the maximum flexibility for all your serial protocol needs, the FT2232H is specially designed to take advantage of several common serial protocols. The board includes an onboard 3.3V regulator, access to +5 and +3.3V if your project is to run on bus power, and a blank EEPROM for configuration data(such as modes, VID/PID).
The available serial modes are: - Dual Channel RS232/RS422/RS485 - Dual Channel 245 FIFO - Sync/Async - Dual Channel JTAG <---------------------- what you need - Dual Channel I2C - Dual Channel SPI - Dual Channel Bit Bang - Sync/Async - Dual Channel CPU style FIFO Interface - Dual Combination of any of the above interfaces - Fast Serial Optical Interface - 8051 Host Bus Emulation
The datasheet can be downloaded from FTDIChip.com. As well, they have information on all the configuration modes, and custom DLL's for the I2C, SPI, and JTAG interfaces.
In order to use a ft2232 as gnICE usb-jtag, you have to program the onboard EEPROM. FTDI has a program called FT_PROG. Download and run the program and parse the FT2232 information. As you can see from the image, after parsing the data, you need to navigate to the hardware settings under each port and select 245 FIFO mode. Once this is done, write the data to the FT2232 chip. I have noticed that the FTDI_Prog seems to have a bug where string descriptors do not get read back right if you change them. As far as I can tell they write properly, but do not read back correctly and appear as garbled characters.
method1: do a custom configuration, programming the ft2232 eeprom
Every FT2232 universal serial module has an EEPROM (1) on board that is programmed with a default set of parameters including the
- VID:0x0403 default
- PID:0x6010 default
- VID:0x0456 gnICE
- PID:0xf000 gnICE
The EEPROM can be changed onboard using the FTDI Windows utility FT_Prog or any other Linux stuff. If you change the VID & PID to match gnice then every software looking for gnICE can detect the module.
(1) EEPROM, AT93C46
method2: hacking urjtag
urjtag is handling is at urjtag/src/tap/cable/ft2232.c & ft2232_list.h This is where the gnice and gnice+ are defined.
so you could aldo modify the urjtag code replacing
URJ_DECLARE_FTDX_CABLE(0x0456, 0xF000, "-mpsse", "gnICE", gnice)
URJ_DECLARE_FTDX_CABLE(0x0403, 0x6010, "-mpsse", "gnICE", gnice)
it has been used here: http://www.mindchasers.com/topics/jtag.htm