usb_jtag using Cypress FX2 chip
===============================

== General information ==

The code in this directory is for Cypress FX2 (e.g. CY7C68013A) and can be
compiled with the SDCC compiler (I tried version 2.6 as shipped with Ubuntu
6.10). Once I had a version that could be compiled with Keil tools (until early
2007), but switched to SDCC because I usually develop on a Linux host.

No logic beside the FX2 itself and only a few external components are required
for a basic JTAG adapter. I don't have detailed schematics available; my test
setup consists of a FX2 on a custom board where it's directly connected to a
Cyclone FPGA.

        ____________
       |            |
       | Cypress    |
  USB__| EZ-USB FX2 |__JTAG(TDI,TDO,TCK,TMS)
       | CY7C68013A |
       |____________|
        __|__________
       |             |
       | 24 MHz XTAL |
       |_____________|


Similar boards are available from fpga4fun.com - the boards named "Saxo-L" and
"Xylo-EM" are pre-wired for use with an adapted version of my code, while
"Saxo" and "Xylo" can be used after soldering 4 extra wires:

	http://www.fpga4fun.com/board_Xylo.html

There's a discussion thread in the fpga4fun forum about this firmware:

    http://www.fpga4fun.com/forum/viewtopic.php?t=483


== Use with Nexys 1 / 2 Boards ==

Through a contribution by Sune Mai, this code can be used with the Digilent
Nexys / Nexys2 boards.

    http://www.digilentinc.com/nexys/
    http://www.digilentinc.com/nexys2/

The hardware-specific code file is hw_nexys.c, just change the line
"HARDWARE=hw_basic" to "HARDWARE=hw_nexys" in the file "Makefile" to use it.

Also, you may use the "nexys2prog" script by Andy Ross, available from the
same place this code is available from:

    http://ixo-jtag.sourceforge.net/


== Adapting the code to your hardware ==

As is, the code assumes the following pin assignment:

 Port C.0: TDI
 Port C.1: TDO
 Port C.2: TCK
 Port C.3: TMS

Other assignments are possible. If you have your signals connected to
bit-addressable I/O pins (port A,B,C or D), I suggest you make a copy of
hw_basic.c and adapt the definitions and ProgIO_Init() in it to your needs.
The file hw_saxo_l is even simpler to adapt if you want only JTAG and no AS/PS
mode.  If your signals are not on bit-addressable I/Os (that is, you're using
port E), you could base your adaptation on the slower hw_xpcu_i.c. You may
specify the name of your adapted hardware-specific file when "make"ing, e.g.:

  make HARDWARE=hw_saxo_l


The USB identification data (vendor/product ID, strings, ...) can be modified
in dscr.a51. The firmware emulates the 128 byte EEPROM that usually holds
configuration data for the FT245 and which can be read from the host; its
content (including checksum) is computed from the data in dscr.a51 as well.  

The WAKEUP pin should be high for the re-numeration to work reliably (thanks
Jean/fpga4fun!).


== Using it with Xilinx JTAG cable ==

There is code to support running in the "Xilinx Platform Cable USB". If you
select HARDWARE=hw_xpcu_i or hw_xpcu_x at the top of the Makefile, a firmware
for the XPCU will be built. I've tested this only with unmodified CPLD version
18 (0x12) on a Spartan-3E starter kit, as it was programmed by my WebPack 8.2i.
The code needs optimization; yet it is merely a proof of concept.
Compile for the XPCU with e.g. "make HARDWARE=hw_xpcu_x".

 hw_xpcu_i: Access "internal" chain (the XPCU CPLD, IC3, itself)
 hw_xpcu_x: Access "external" chain (the Spartan 3E, PROM, etc.)


== History ==

Changes since previous release 2008-07-05:
  - Imported to SourceForge, please see the project page:
    http://ixo-jtag.sourceforge.net/

Changes since previous release on 2007-02-15:
  - Jean Nicolle contributed hw_saxo_l.c for the FX2 boards from fpga4fun.com
  - fx2/Makefile fixed to build correct libfx2.lib even under Windows.

Changes since previous release on 2007-01-28:
  - Initial suppport for running on Xilinx XPCU.
  - New FX2 code, based on USRP2 from the GNU Radio Project;
  - Firmware can now be compiled using SDCC 2.6. No more Keil support.
  - EEPROM content is automatically computed from dscr.a51, including checksum.

Changes since initial release on 2006-04-23:
  - added this readme.txt
  - reorganized my project folder: diff now created from Subversion repository
  - stripped *.dist extension from eeprom.c and dscr.a51 
  - added unique proper product and vendor ID (thanks to Antti Lukats!)
  - fixed checksum in eeprom.c
  - added comments about AS/PS mode pins in usbjtag.c

