Hey Folks,
I've been meaning to post this, but got tied up in
beginning-of-semester administrative stuff.
Beyond making sure the FPGA on the interface board puts out the
correct voltage levels, I wanted to start a discussion on exactly how
we're going to get a bitstream into the FPGA. Obviously, we'd like
the Beagleboard to be able to program the FPGA directly, but I think
a good backup plan would be to make sure the FPGA can be programmed
independently.
I don't have a whole lot of experience developing FPGA programming
interfaces (I usually just stick a JTAG connector on the board),
however, the Cyclone III can be set up to use a dual JTAG/Active
Serial interface. From my perspective, that's a plus, as we can put
a memory chip in the AS chain that will automatically program the
stored bitstream into the FPGA on powerup. Also, the JTAG has a mode
where a microprocessor can download a bitstream into the FPGA from an
external memory location (e.g., you could have the bitstream stored
on an SD Card and program it through the OMAP3).
The catch to using the JTAG mode is that it requires dedicating 4
pins on the expansion header to connect to the JTAG pins on the
FPGA. Obviously, we could make judicious use of Zero-Ohm resistors
so that an end user has the option of not using the JTAG programming
(and reclaiming those pins).
The big question I wanted to throw out there is: Is this a viable
method of programming the FPGA? Does anyone have any suggestions for
other/better options? I'd like to keep the AS method out there, as
the students will feel better if they can program the FPGA directly
(i.e., they can still demonstrate that the board works and get an "A").
Chris
-------------------------------------
Chris R. Anderson, Ph.D.
[EMAIL PROTECTED]
410-293-6185
Assistant Professor
US Naval Academy
Electrical Engineering Department
105 Maryland Avenue
Annapolis MD 21402
