XESS

I woke up famous this morning: my interview was online. Thanks to EEWeb for providing the opportunity and the venue. (Make sure to scroll to the bottom for a list of interviews with other engineers almost as fascinating as me.)

A new VHDL textbook was released a few days ago. *Yawn*, right? There's like a hundred of those on Amazon already.

But the good thing about this one is that it covers the basics of using VHDL in a concise and attractive 129 pages. It goes over the syntax and semantics of the language and illustrates behavioral and structural description styles with an emphasis on synthesis. But you don't have to take my word that this book is good - you can download Free Range VHDL for free!

Well, it's Thanksgiving in the USA. A few years ago, at a gathering of my girlfriend's family, we each made lists of things we were thankful for. "Family" and "togetherness" appeared quite a bit, but my list, naturally, was a bit different - it had things like "clean water" and "absence of minefields" on it.

I wrote last month about using Upverter, and now there's a new OSHW repository on the scene: Solderpad. While Upverter is trying to provide both cloud-based design tools and a repository, Solderpad has taken a more modest path and provides only a place for you to store your designs after you've used whatever tool you want to create them. So you might ask how that's any different from just storing your design on Github. Well, in addition to the Git-based repository, Solderpad adds these capabilities:

• You can pan-and-zoom on a multi-page schematic of a design.
• You can pan-and-zoom on a view of the PCB of a design.
• You can view and download a bill-of-materials (BOM) for a design. You can also click on a component in the BOM and get a bunch of information about it from Octopart, which is pretty neat.

As FPGAs work their way into the hobbyist/maker community, I'm guessing a lot of you are trying to learn VHDL and Verilog. (You can try to use schematics, but the Xilinx editor is pretty poor.) Which language you choose is up to you, but I'll only talk about VHDL in this post. There's general agreement that if you know one, it's easy to learn the other.

There's no shortage of VHDL books (around 100 on Amazon) or online tutorials (Google lists 278,000 but I haven't checked them all), so there's no need for me to waste my energy doing another. Instead, what I will do is tell you how to use the existing books & tutorials to learn the use of VHDL in synthesizing logic for FPGAs.

This is how things get out of hand...

I was making a clone of my hard drive to keep at my sister's place. (I do this in case my ex-wife ever decides to come by and burn my house down.) As I'm sitting there doing other things, I notice the computer reboot while there's still two minutes to go on the cloning countdown timer.

"That's weird.", I thought, "That's probably not a good thing."

Upverter is a website/service that allows people to collaborate on hardware designs. It looks like they've got some VC funding and they're pitching themselves to the OSHW community as the place to store their designs.

A DangerousPrototypes blog post called Upverter a "closed source vampire" for trying to profit from the OSHW community while still keeping their web-based tools closed. Kinda harsh. Without knowing the Upverter people's true intentions, I can't say if it's true or not. Regardless, I don't care. I'm a pragmatist and I'll use anything that's effective - open or closed - to get my design done.

I get some comments like this: “All the other FPGA boards have loads of blinking LEDs. And they have bunches of buttons and switches! My XuLA board has nothing!”

A few years ago, my sister and I decided to plant a stand of corn in addition to the regular garden on her farm. This entailed tilling a 50' x 15' area, hoeing the dirt up into about twenty mounds, shaping the mounds for holding water, punching four holes in each mound, and, finally, placing a few kernels in each hole. Then we planted beans among the mounds to try and crowd out the weeds.

Some people have commented that the 12 MHz clock on the XuLA FPGA board is too slow for practical use. What they've missed is the Spartan-3A FPGA has on-chip digital frequency synthesizers (DFS) that can multiply the clock to over 300 Mhz. To show how easy it is to do this, I've added another chapter on using the DFS to my new book about doing FPGA design using Xilinx ISE WebPACK and the XuLA board. It just takes a few lines of VHDL and you can have almost any clock frequency you want between 5 MHz and 320 MHz.*