Getting started with FPGAs: choices on HDL and devboards

[MacAttak]

Mojo is still on pre-orders 

They are very new (just launched about 2 weeks ago), and now that the initial pre-orders will have all been shipped this week I think they are opening up web orders again. This was launched through Kickstarter, so those boards had higher shipping priority than any web-based orders.

This board won't have all of the bells and whistles that a typical dev board might, but it is quite approachable and the vendor has been producing decent tutorials for the board (in Verilog) which are beginner-focused... starting with simple stuff like blinking an LED up to PWM and I/O.

[marshallh]

The biggest advantage of VHDL is that it is a lot like a programming language. Like Pascal its roots lie in Ada. The thing is that a lot of designers use VHDL to describe logic equations. That takes a lot of typing indeed.

In my experience one should approach an FPGA design as writing a piece of software and just don't care about how it is translated into hardware. VHDL offers a lot of powerful tools like functions and records (the C equivalent of a structs) which make life so much easier. A clever function can replace dozens of lines of code. A record can be used to easely convey a whole bunch of signals throughout a design like passing a pointer to a struct in C. It really pays off to study VHDL's advanced features.

 


 

[nctnico]

So I guess you still program everything in assembly language 

[free_electron]

So I guess you still program everything in assembly language 

come talk to the people that are trying to minimize the die-size.... or are trying to do the timing closure on your convoluted design...
designing hardware is not designing software ...

[nctnico]

If silicon is expensive... most people work on low / medium volume products where time to market is far more important than saving a dollar on component costs.  I've seen many projects where a lot of time and money got wasted because people tried to save pennies on components. Penny wise pound foolish 

Besides that developing code for an FPGA is exactly the same as writing software. There is a function Y which needs to be implemented with resources X in development time T. If you make X large then T gets small and vice versa. Unfortunately this relationship is exponential. If you make X smaller then T increases exponentially.

[ivan747]

Mojo is still on pre-orders 

They are very new (just launched about 2 weeks ago), and now that the initial pre-orders will have all been shipped this week I think they are opening up web orders again. This was launched through Kickstarter, so those boards had higher shipping priority than any web-based orders.

This board won't have all of the bells and whistles that a typical dev board might, but it is quite approachable and the vendor has been producing decent tutorials for the board (in Verilog) which are beginner-focused... starting with simple stuff like blinking an LED up to PWM and I/O.

Sounds good, if the price is right. I still prefer the Lattice board so far.

[free_electron]

whoa. stay away from lattice ! talk about sucking development tools !

stick to Altera or xilinx.
best devtool is still altera quartus.

[mikeselectricstuff]

whoa. stay away from lattice ! talk about sucking development tools !

stick to Altera or xilinx.
best devtool is still altera quartus.

Maybe (never used it but hear good things) but Altera have nothing at the low end of the market that competes with Lattice or Xilinx, and Lattice go a lot lower than Xilinx at the lowest "only just need an FPGA" end. Probably less difference as you go up in size.   
Lattice software seems to be pretty much the same as Xilinx ISE in many respects and I'd be highly surprised if most of the code wasn't the same, less umpteen gigbytes of useless bloat of device files for devices you can't even use with the free version.
Unlike Xilinx and Altera who have a PITA distribution system where you need to ask for quotes on production qtys, you can get quantity pricing easily from Digikey etc. on Lattice parts. 

[ivan747]

I don't think I will ever start a project complex enough to fully use the potential of a $60 FPGA. I found a handful of cheap boards searching around. I'll take a look in detail. I like Lattice's concept of having low end CPLDs for when you just need simple things. That's probably going to be my main use for programmable logic anyway.

[mikeselectricstuff]

Here's a very cheap FPGA board option, albeit with minimal IO accessible
http://hackaday.com/2013/05/08/hdmi-color-processing-board-used-as-an-fpga-dev-board-to-mine-bitcoins/

[ivan747]

Here's a very cheap FPGA board option, albeit with minimal IO accessible
http://hackaday.com/2013/05/08/hdmi-color-processing-board-used-as-an-fpga-dev-board-to-mine-bitcoins/

Just saw that. The time spent getting the thing to work properly for the first time isn't worth it, but hey, nice hack.

The second last thing I want is to try to debug a learning tool. The last thing is debugging a debugger...
I'm going for the Lattice devboad. It's readily available and I like it. Some say the software is bad but I've tolerated MPLAB X 1.0 so their software cannot be that bad.

[gocemk]

Hi everyone,

This is my first post on this forum, but i've been visiting here for a while now.
I wanted to learn how to work with FPGA's, so i ordered this Open3S250E (actually mine is 3S500E):

http://www.ebay.com/itm/XILINX-XC3S250E-Spartan-3E-FPGA-Development-Board-LCD12864-LCD1602-12-Kits-/261135683246?pt=LH_DefaultDomain_0&hash=item3ccce64eae

from ebay along with the appropriate usb jtag programmer and a few other items (sd card board, GLCD, and keypad). It says that it comes with Xilinx ISE 12, and with examples with both Verilog and VHDL. So, i was wondering if any of you had any experience with this dev board and maybe can share something?
I am still waiting for it to arrive, so maybe i'll post some pictures of it later.

Thanks!

[joelby]

I maintain a list of cheap FPGA development boards, which you might find interesting.

Personally, I would recommend spending a bit more to get a development board that includes some of the more interesting peripherals that an FPGA can talk to.

With a microcontroller, you can connect many of the external things you'd use with a few loose wires. An FPGA can talk to gigabit Ethernet PHYs, DDR memory, HDMI transceivers, PCIe buses, and so on. These high speed interfaces require attention to signal integrity and trace length matching during design and thus are much harder (or impossible) to breadboard on to a generic development board. I think that learning about these more complicated interfaces is good for developing more advanced FPGA experience.

[ivan747]

I maintain a list of cheap FPGA development boards, which you might find interesting.

Personally, I would recommend spending a bit more to get a development board that includes some of the more interesting peripherals that an FPGA can talk to.

With a microcontroller, you can connect many of the external things you'd use with a few loose wires. An FPGA can talk to gigabit Ethernet PHYs, DDR memory, HDMI transceivers, PCIe buses, and so on. These high speed interfaces require attention to signal integrity and trace length matching during design and thus are much harder (or impossible) to breadboard on to a generic development board. I think that learning about these more complicated interfaces is good for developing more advanced FPGA experience.

I have read this list as well as this website:

http://www.fpga4fun.com/

Thanks for the list. I am still considering my choices, but the site I mentioned has a great introduction I can use to guide myself and your list is a great place to get started.

Update: Dave should do an FPGA introduction/tutorial series. If he splits the tutorial into several videos he will get hundreds of thousands of views combined.

[mikeselectricstuff]

I maintain a list of cheap FPGA development boards, which you might find interesting.

Lattice XO2 board I linked to earlier in the thread isn't there

[ivan747]

Lattice XO2 board I linked to earlier in the thread isn't there

Mike, I have a question. On your iPod screen hacking video, part 2, is the CPLD operating at full capacity? And by that I mean, how many blocks were taken and if that is the maximum framerate you could get from it.
I'm asking because that board is the Lattice XO2.

[mikeselectricstuff]

Lattice XO2 board I linked to earlier in the thread isn't there

Mike, I have a question. On your iPod screen hacking video, part 2, is the CPLD operating at full capacity? And by that I mean, how many blocks were taken and if that is the maximum framerate you could get from it.
I'm asking because that board is the Lattice XO2.

Not much (see image)  but the logic isn't very complicated. On my PCB I used the 1200, of which it used maybe 50%, but there is significant unnecessary logic for test & debug (e.g. serial commands to send DSI packets from the PC). I'm sure it would fit a 640 part without much effort
It currently takes 35mS to display a frame from flash, but this is just limited by me not having yet implemented wide flash transfers as I had to get something built & working quickly. Bandwidth to the display is not an issue - I had it running at 99MHz, but slowed it down to make it easier to debug on the cope. - It could easily do 60FPS.
 

[ivan747]

More than capable for my needs, thanks!

[glatocha]

I would like to go back to the HDL question. From the future employment point of view, which Verilog or VHDL is better?
More widely used and so on?

[nctnico]

If you are in Europe: VHDL, if you are in de US: Verilog. I don't know about the rest of the world.

[joelby]

I don't think it's too hard to move from one to the other. The syntax is a bit different and VHDL is strongly typed, but the concepts as they apply to FPGAs are the same. Perhaps concentrate on whichever one is dominant in your geographic area, but make sure you're familiar with the other too.

[ivan747]

Would this be a good Verilog tutorial? I feel the author treats it more like a programming language than an HDL, but I'm not sure if this is the way it should be typed. 

Here's a page from it talking about the always blocks:
http://www.asic-world.com/verilog/verilog_one_day3.html

[joelby]

It's probably a little brief, but it might be okay as a basic introduction to the syntax. It doesn't make it very clear which parts of the language are synthesisable and which aren't (and what this actually means to you).. but to be fair it's a Verilog tutorial and not an FPGA synthesis tutorial.

I'd probably recommend Pong Chu's books (there are identical Verilog and VHDL versions) though they're expensive and I don't love absolutely everything about them.

[glatocha]

I found yesterday this course recorded. I didn't watch it yet, but maybe worth to give it a try

[nctnico]

I don't think it's too hard to move from one to the other. The syntax is a bit different and VHDL is strongly typed, but the concepts as they apply to FPGAs.

Bad mistake. VHDL is a full blown programming language where Verilog is a netlist format. If you are used to using the full potential of VHDL then switching to Verilog will be a cold shower.