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Thursday, September 4, 2014

FPGA - My second FPGA dev board

I am back playing with FPGAs.
Meanwhile I bought a new FPGA borad, not that the tiny one I already had did not do, but I found that connecting and disconnecting stuff all the time to the GPIO was not really a convenient way to go.
So I went for another Cyclone IV board, a bit more expensive, but it has a bit of everything onboard.
Most of all it has external SDRAM, a VGA connector, Ethernet, an internal B/W LCD, some 7 segment leds, USB, a buzzer...
Looks like a perfect platform for Nios II stuff.

This board is a Black Gold Cyclone IV EPCE15 (15K LEs) which seems to be designed and built with some quality criteria in mind.
Not sure what the exact brand is as I found references to Alinx, and OSH (you can see an OSH logo in the picture, top right).
The url on the bottom right part says , but that appears to be a domain for sale :)

Ok, not exactly a Terasic product, we get it, right?
Still they went the extra mile and packaged the whole thing in two plastic transparent sheets (laser cut), PCB finish seems to be really nice and you get an amazingly good looking box which even has magnets to keep the front flap closed (I know, it is a tiny useless detail, but at least it shows they are trying to give a quality image, which never hurts).

In my case the box contained the assembled board, a psu, an usb blaster with cables and a vga cable plus a container with 3 DVDs.
Yup, 3 DVDs of docs, samples, software, videos illustrating every single experiment included... which is all great provided you can read Chinese.
It seems there are detailed instructions for every single step, every single detail, but not a word in English.
Actually the parts datasheets are in English once you find them in a folder structure that has Chinese directory names.
Same thing if you try to find something in internet, looks like there is plenty of info there, but pretty much none in a  language I can understand.
Looks like it's a good time to start learning Chinese, after all, I wish they taught me that instead of Latin back when I was young!
Now I already speak 3 languages (plus I can curse in Latin too, does that count as a 4th?) and about learning a 4th which has a complex and completely new (to me) alphabet... call me lazy, but, seriously, I am already trying to learn FPGAs, I might pass on this one!

Finally, scavenging in the discs and renaming folders in a way I can understand them, I found a lot of useful material.
Verilog is Verilog, schematics are schematics and to be fair there are very few times when I found comments that were decent enough to be somewhat useful, so, no big deal if they are written in Chinese after all!

Verilog modules and variables in the examples are in English, plus you get a separate folder with a full Quartus II project for each experiment.

I already tried most of the experiments and started to modify a few of them.
Particularly I focused on the VGA interface, which -at least on this board- is not really suitable for a practical purpose.
The signal appears not to be clean enough (might require some proper shielding) and the color depth is only 3 bit (1 bit per color component).
On top of that the voltage I get for each color component seems to be too low, so, what you would expect to be a white pixel (111) turns out to be a pale grey.
Maybe toying around with the IO bank settings on the Cyclone IV could solve that last issue.
That said, all is completely fine to run experiments and learning from them.
I will write another post about VGA, here a picture of a binary color pattern I did yesterday (is it a form of art? :) )

Meh, I know, kinda useless, right?
That's why I call it art!
Seriously that kind of experiment makes you realize how a VGA sync module works, how to interface with it etc and from a dev perspective, with FPGAs, the  color depth does not change much your design.

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