I think it might be worth while to make a small PCB that will do the
level shifting between the Cyclone III starter kit and the Beagle
Board expansion header.
There is no 1.8V reference coming from any of the expansion headers on
either of the boards, but the IO pins on the CIII FPGA board is 2.5V
and the OMAP pins are 1.8V.
The CIII board supplies both a 12V and 3.3V power rail and the Beagle
Board supplies a 5V and 1.8V rail. Since none of these actually have
the 2.5V rail that the IO has, it seems a regulator is going to have
to be used on the board. The good news is there are plenty of
supplies available to tap.
While it may not be the most ideal option, I suggest a quick
interfacing board that has:
- Header to connect to Beagle Board
- Header to connect to Cyclone III Starter Kit
- Prototyping area for unused Cyclone III Starter Kit pins
- Regulator to provide 2.5v supply (can run off either 12V, 5V or
3.3V rails supplied)
- Bidirectional level translators
(http://www.analog.com/en/interface/level-translators/ADG3308/products/product.html)
The level translators support up to 50Mbps officially, and while it's
a little slow, the MMC interface is supposedly clocked at 52MHz (max)
and the McBSPs can run at that rate as well.
To get something going quickly, and with boards that are viable off
the shelf, this seems to be a pretty quick and easy way to get the
Beagle Board talking with a cheap (yet still pretty powerful) FPGA dev
kit.
Brian
