FPGA board

Mathew Benson mathew.benson at gmail.com
Wed Apr 3 12:34:32 UTC 2013

I have been evaluating inexpensive FPGA based boards to eventually port RTEMS.  I have the XuLA2 (http://www.xess.com/prods/prod055.php), and started with the OpenRISC.  XuLA2 has a Spartan 6 LX25 and 32 MB of SDRAM and costs $119.  I got the OpenRISC core loaded but switched to Microblaze before I tried running code on it.  With the minimum options, OpenRISC takes up about 90% of the area and looks like a jumbled mess.  Microblaze takes up 25% and looks clean.  I can't get the OpenRISC to pass timing tests over 50 MHz.  Microblaze goes up to 100 MHz.  But, the Xilinx tools don't support the XuLA2 SDRAM.  I will have to eventually find or write my own SDRAM controller.  The Xilinx software development tools don't support the XuLA2 loader, so I purchased a Xilinx JTAG.  Now I'm having problems getting the XuLA2 to work with JTAG, but I finally got an email from the manufacturer.  

I just purchased a beta Pipistrello board (http://pipistrello.saanlima.com/index.php?title=Welcome_to_Pipistrello) which should arrive Friday.  They will be available in multiple sizes with the largest being the Spartan 6 LX45 for $149.  It has 64 MB of DDR SDRAM, which is supported by the Xilinx tools.  It also has a USB loader, though the beta board does not.  It has more pins but is a larger board than the XuLA2.  He expects to make production boards available in the next couple weeks.  What I really find interesting is that he already has Linux running on a Microblaze core on it and has posted files and instructions on his website.  He even has Arduino ported with the Arduino SDK and IDE ported and available on his site.  The LX45 is almost twice the size of the LX25, and I believe the Pipistrello uses the faster -3 grade FPGA.  I've read people have even fit software based radios into the LX45.  Lastly, I've been getting better support on Pipistrello.

I like the XuLA2 because of the smaller physical size, low cost, and the fact it's breadboardable, but the Pipistrello is better in every other aspect.  Once I get the Pipistrello, I want to start porting RTEMS to the Microblaze.
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