usbjtag - Variations on the implementation of a USB JTAG adapter.Copyright (C) 2005,2006 Kolja Waschk, ixo.de----usbjtag is free software; you can redistribute it and/or modify it under theterms of the GNU General Public License as published by the Free SoftwareFoundation; either version 2 of the License, or (at your option) any laterversion.usbjtag is distributed in the hope that it will be useful, but WITHOUT ANYWARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FORA PARTICULAR PURPOSE.  See the GNU General Public License for more details.You should have received a copy of the GNU General Public Licensealong with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA----== Purpose ==The goal of the project was to build a budget USB JTAG adapter. Basicallyit should allow direct I/O access to the JTAG signals from an USB host, butadditionally implement some sort of parallel/serial conversion as well forhigher transfer rates. While a combination of USB I/O device like FTDI FT245BMwith a custom logic for the parallel/serial conversion could be used, I startedwith a prototype implementation in software on a Cypress EZ-USB FX2 controller.That happens to be the controller in a device manufactured by my employer,where it is used to configure an Altera Cyclone device. That gave me a niceplatform for testing.I release the code for this homebrew firmware here. FX2 code is in the fx2/subdirectory. The "usbjtag.c" file contains a descriptive text about themechanism how the host PC controls the JTAG chain via USB. Before compiling,you'll have to rename the *.c.dist files to *.c!For people who like to read VHDL better than C or English, I later also wrotecpld/jtag_logic.vhd. When synthesized with Altera's Quartus II, its logic fitsinto an EPM7064 CPLD and can interface to a FTDI FT245BM USB controller. Both "hardware variants" are now interchangeable; the FX2 behaves like theFT245BM with CPLD. It even simulates the EEPROM that has to be attached to theFT245BM for configuration of Vendor ID etc. (but it ignores most of the extraconfiguration sent by FTDI drivers to the FT245BM).== USB IDs ==Because I do not have a vendor ID, the "0x6666" prototype vendor ID is used.This should never ever appear in any device to be used outside your lab/homeenvironment! To use a different ID, change eeprom.c and dscr.a51 accordingly.== Hardware ==Unfortunately, I do not have the time to present finished schematics for eithervariant of the USB JTAG adapter. As the source is quite incomplete anyway, ifyou're using it you're probably one of those people who easily can make uptheir own schematics. In principle, they are like the drawings below (bestviewed with fixed-width font!). Add power supply, voltage regulator(s), levelshifter, termination resistors, and more, as required...Variant A: Cypress FX2 as USB JTAG Adapter, booted from host PC (no EEPROM)              ____________             |            |             | Cypress    |        USB__| EZ-USB FX2 |__JTAG(TDI,TDO,TCK,TMS)             | CY7C68013A |             |____________|              __|__________             |             |             | 24 MHz XTAL |             |_____________|Variant B: FTDI FT245BM plus EEPROM 93C46 plus CPLD EPM7064              _________             |         |             | AT93C46 |             |_________|              __|__________    _________             |             |  |         |        USB__| FTDI 245BM  |__| EPM7064 |__JTAG (B_TDO,B_TDI,B_TMS,B_TCK)             |_____________|  |_________|              __|__________    _|___________             |             |  |             |             | 6 MHz XTAL  |  | 25 MHz Osc. |             |_____________|  |_____________|== Notes ==Both variants haven't been gone through thorough testing, so please do notconsider it "production quality"!I have only included code here that is purely my own work or taken from Cypresslibrary for the FX2 firmware.  If you include support for this device in yourhost software, please let me know, so I can mention it in this README. And then please be so kind to include support for the USB-Blaster made by Alterain your software as well, because: if your software does work with the FTDI +CPLD variant presented here, chances are good that it could also make use oftheir adapter (VID 0x9FB, PID 0x6001, "Altera" / "USB-Blaster"). But beware!Don't conclude that my adapter could be used as a substitute for an Alteraadapter. It doesn't support Active/Passive serial mode and it certainly isn'tlegal to build something that pretends to be made by someone else!!!Quartus and USB-Blaster are trademarks of Altera Corporation.