simple commandline jtag stuff


Quick hack commandline tools to interact with Altera FPGA Virtual JTAG interfaces,
using the USB Blaster device (as integrated on Terasic dev boards, etc).

Not terribly fancy or optimized but only depends on libusb-1.0

Currently does not support multiple devices on the chain.

jtag.c - provides simple jtag interface
jtag-virtual.c - provides simple virtual jtag interface

jload.c - example of using the virtual jtag interface for a downloader interface
          with a CTRL/ADDR/DATA register set.  CTRL[0] asserts reset, writes to
          DATA store to [ADDR] and auto-increment ADRR.

jinfo.c - dumps idcode and virtual jtag hub and device info table

Why?  Scripting the Altera quartus_stp tool in TCL was driving me nuts.