Author Topic: Absolute bare minimum FPGA thats breadboardable?  (Read 3809 times)

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Offline cvriv

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Absolute bare minimum FPGA thats breadboardable?
« on: January 11, 2022, 07:07:35 pm »
I want to get into FPGAs but I dont want a kit with all the bells and whistles. I want the absolute bare minimum so I can do it all myself and learn. I think id love to just have a FPGA presoldered to a breakout board that i could connect to a breadboard. Kind of like the CMOD FPGA boards. I cant find any bare kits like what i want. Any ideas?
 

Offline dorkshoei

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Offline mikeselectricstuff

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Offline asmi

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #4 on: January 11, 2022, 07:24:58 pm »
There are a few toy FPGA (like the tinyFPGA listed above), but most serious FPGAs are simply not breadboardable due to a whole host of issues like complex power delivery, signal integrity issues, etc. If you want to see what it takes to design a custom board for somewhat modern FPGA - take a look at the project in my signature. It's not barebones because while aimed at beginners I still wanted to make it practically useful, but it's open source so you can remove anything you don't want while keeping all essentials there, and design your own board.

Offline nctnico

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #5 on: January 11, 2022, 07:42:14 pm »
I want to get into FPGAs but I dont want a kit with all the bells and whistles. I want the absolute bare minimum so I can do it all myself and learn. I think id love to just have a FPGA presoldered to a breakout board that i could connect to a breadboard. Kind of like the CMOD FPGA boards. I cant find any bare kits like what i want. Any ideas?

Something like this:
https://www.seeedstudio.com/Sipeed-Tang-Nano-FPGA-board-powered-by-GW1N-1-FPGA-p-4304.html

I have used this FPGA in a project and it is quite straightforward to use.
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Offline fourfathom

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #6 on: January 11, 2022, 07:51:00 pm »
There are a few toy FPGA (like the tinyFPGA listed above), but most serious FPGAs are simply not breadboardable due to a whole host of issues like complex power delivery, signal integrity issues, etc. If you want to see what it takes to design a custom board for somewhat modern FPGA - take a look at the project in my signature. It's not barebones because while aimed at beginners I still wanted to make it practically useful, but it's open source so you can remove anything you don't want while keeping all essentials there, and design your own board.

I wouldn't call that tinyFPGA a "toy", but yes, it's limited.  I've used the larger tinyFPGA "BX" board to prototype a design with multiple inputs in the 100-200 MHz range, and lots of high-speed internal logic as well as an on-chip PLL.  It was easy to use and did the job.  I've also soldered a Lattice MachX02-1200 onto a small breakout board with the bypass caps tacked across the header pins.  and the whole thing plugged into a protoboard.  No doubt the signal integrity wasn't as good as with a proper PCB layout, but it certainly worked well enough for me to do some good testing and development.

Of course the Spartan-7 board asmi has uses a faster and more capable FPGA than my MachX02-1200, so it depends on what you want to do.
 

Offline SiliconWizard

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #7 on: January 11, 2022, 07:55:57 pm »
Have you looked at the Cmod S7 Fred27 suggested?

And there are a handful more such boards. The OrangeCrab with an ECP5 for instance.
Sure those boards are limited in some ways, but if the OP is looking for exactly that - a breadboardable FPGA board - then certainly they can have at it.
 

Offline dorkshoei

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #8 on: January 11, 2022, 08:00:09 pm »
Have you looked at the Cmod S7 Fred27 suggested?
[tangent] $70 seems a bit spendy to me for a bare bones product but that's the Digilent stuff for you.
« Last Edit: January 11, 2022, 08:03:42 pm by dorkshoei »
 

Offline asmi

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #9 on: January 11, 2022, 08:56:18 pm »
[tangent] $70 seems a bit spendy to me for a bare bones product but that's the Digilent stuff for you.
For that money you are getting a real FPGA with over 25K LUTs, not a toy with measely 256 LUTs. So on a LUTs per $ scale that Digilent board is at least an order of magnitude better value.

Offline BrianHG

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #10 on: January 11, 2022, 09:02:00 pm »
There are 2 units still stock of the 37$ Arrow DECA boards.  You are getting quit a bit for that price, not to mention the FPGA has 50kgates and the onboard DDR3, ethernet, USB, hdmi, and SD card slot plus additional flash ram. And it comes with cables and external power supply, or can be powered from one of the USB ports with functional demos and a Quartus setup template so you do not need to worry about messing up all the IO positions.
« Last Edit: January 11, 2022, 09:04:07 pm by BrianHG »
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Offline kizmit99

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #11 on: January 11, 2022, 09:36:46 pm »
I've had fun with boards like the following:
https://www.ebay.com/itm/284411856560?hash=item42384486b0:g:SzAAAOSwjRdhGg4r

It's basically just an Altera Cyclone II with power circuits on a PCB with a bunch of headers.  It's certainly not cutting-edge FPGA tech at this point, but in my opinion a very capable device for learning...

Note that the ebay link above was simply the first current listing I found - the price $34 seems absurdly high to me.  I have bought these in the past for between $12 and $15 each (in qty 1) - so if you do decide to go that route - search around for a better price.
 

Offline cvriv

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #12 on: January 11, 2022, 09:43:00 pm »
Wow. So many replies and so quickly too. Thanks. Im going to read through all your suggestions. I think i might get the CMOD S7 but also maybe one or two of the cheaper ones too just so i have a variety to mess with. Thanks again for the help!
 

Offline rstofer

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #13 on: January 12, 2022, 12:19:13 am »
I'm going to vote for the Digilent board and recommend you don't buy another brand right now.  It's about the toolchain!  You will spend a lot of time getting familiar with the tools and the hardware is almost an afterthought.  Pick a vendor based on their tools and use their products until you have a good deal more experience.

 

Offline cfbsoftware

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #14 on: January 12, 2022, 03:29:53 am »
I'd also highly recommend a Digilent board - their documentation is always very good. The CMod-S7 is hard to get right now, but the CMod-A7 is still available:

https://digilent.com/reference/programmable-logic/cmod-a7/start
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Offline brucehoult

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #15 on: January 12, 2022, 07:24:17 am »
[tangent] $70 seems a bit spendy to me for a bare bones product but that's the Digilent stuff for you.
For that money you are getting a real FPGA with over 25K LUTs, not a toy with measely 256 LUTs. So on a LUTs per $ scale that Digilent board is at least an order of magnitude better value.

I guess it depends what you want to do.

256 LUT4s and 2 k bits of distributed RAM is not much -- but it might almost be enough to implement a small CPU core. If you boringly used every LUT to implement a 4-input NAND or NOR or AND gate then it would be equivalent to 128 good old TTL 74LS20, 74LS22, 74LS29 chips. Or a whole lot more than that for more complicated functions. A LUT4 can implement a 2:1 mux with a bonus "enable" input. Or the sum or carry for a 1 bit full-adder -- so two LUTs can do the job of a lot of 2-input gates -- 2 AND, 2 XOR, 1 OR or 9 2-input NAND. So that's somewhere between 0.5 and 1 TTL chip per LUT.

Maybe half a TTL chip per LUT would be a good average, given you'd sometimes be using MSI TTL not just the original SSI. 128 chips is a pretty decent sized board, and it will cost a lot more than $13, and use a lot more power too.

Of course 16k LUTs for the CMOD S7 or whatever is a lot better if you have a use for them.
 

Online woofy

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #16 on: January 12, 2022, 10:32:11 am »
I also would recommend the DECA board. It has loads of I/O that you can easily link across to your breadboard and represents astounding value for money. You can still do the simple stuff and ignore the bell & whistles until you need them - and you will.

Offline asmi

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #17 on: January 12, 2022, 04:23:43 pm »
Of course 16k LUTs for the CMOD S7 or whatever is a lot better if you have a use for them.
Don't forget that S7 has LUT6, not LUT4. So a single LUT can do more in many cases as well. This is not to mention much faster fabric in general.

In my book anything less than 15K LUTs is a toy as it's generally not suitable as a main processing device, and is more of a companion chip to a main processing device.

Offline dorkshoei

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #18 on: January 12, 2022, 04:25:49 pm »

In my book anything less than 15K LUTs is a toy as it's generally not suitable as a main processing device, and is more of a companion chip to a main processing device.

Did the OP say he wanted it as a MAIN processing device?   He said he's trying to learn. "I want to get into FPGAs .... and learn".  Maybe he does want 25K LUTs or maybe he doesn't.
« Last Edit: January 12, 2022, 04:28:39 pm by dorkshoei »
 

Offline asmi

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #19 on: January 12, 2022, 04:31:05 pm »
Did the OP say he wanted it as a MAIN processing device?   He said he's trying to learn. "I want to get into FPGAs .... and learn"
And that's fine. Toys are useful for learning. But just don't kid yourself as to what it can or can not do.
I sometimes read Digilent support forums, and I noticed that all too many beginners have unrealistic expectations and end up being disappointed when the board they purchased can't do what they want it too. So setting expectations right is super-important.

Offline dorkshoei

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #20 on: January 12, 2022, 04:35:05 pm »
Did the OP say he wanted it as a MAIN processing device?   He said he's trying to learn. "I want to get into FPGAs .... and learn"
And that's fine. Toys are useful for learning. But just don't kid yourself as to what it can or can not do.
I sometimes read Digilent support forums, and I noticed that all too many beginners have unrealistic expectations and end up being disappointed when the board they purchased can't do what they want it too. So setting expectations right is super-important.

I have no clue what the OPs expectations are.  Why not ask?   You may be right in what he needs,  or not.     I view this as his thread and getting into a debate about what is or isn't a toy seems tangential.
 

Offline rstofer

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #21 on: January 12, 2022, 04:40:34 pm »
I'd also highly recommend a Digilent board - their documentation is always very good. The CMod-S7 is hard to get right now, but the CMod-A7 is still available:

https://digilent.com/reference/programmable-logic/cmod-a7/start

And spend the extra $14 to get the 35T variant.  I personally prefer the 100T variants where available if for no other reason than they have more BlockRAM and you simply can't have too much internal RAM.

I have that Digilent device...

See page 3

https://www.xilinx.com/support/documentation/data_sheets/ds180_7Series_Overview.pdf
 

Offline fourfathom

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #22 on: January 12, 2022, 05:45:43 pm »
And that's fine. Toys are useful for learning. But just don't kid yourself as to what it can or can not do.
You seem pretty hung up on the "toy" characterization, and that's hardly fair.  Smaller and simpler devices can be extremely useful and much more than toys.  As we have been saying, it depends on what you need (or want) to do.
 

Online Cerebus

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #23 on: January 12, 2022, 06:43:19 pm »
And that's fine. Toys are useful for learning. But just don't kid yourself as to what it can or can not do.
You seem pretty hung up on the "toy" characterization, and that's hardly fair.  Smaller and simpler devices can be extremely useful and much more than toys.  As we have been saying, it depends on what you need (or want) to do.

When I hear that kind of characterisation, that something is a toy because it only offers relatively modest capabilities versus something high end, I can't help but think the person making the characterisation either doesn't know how to design things to be efficient and needs all that real estate just to get something simple done (e.g. we all know people who take megabytes and lots of MIPs to do something that many of us can do with a few bytes and a few hundred CPU cycles AKA "python programmers"  :))  Or they are compensating for other feelings of inadequacy - cf "big car syndrome".  Or it's like the boss who needs the biggest and fastest computer in the office just to read emails and surf the web, pure self aggrandisement. I'm not saying that is the case here, just that it's what that kind of posturing always makes me think.

As far as FPGAs that have modestly sized and modestly priced breakout boards available (on the same scale as bluepill and blackpill boards for STM32 microprocessors) there are quite a range of boards for the Lattice iCE40 series of FPGAs. I won't recommend specifics, as the one I have personal experience of, the original upduino, is no longer available (it was all of $7 for a complete board with a 5k LUT FPGA!!!). There have been other boards produced under the 'upduino' name that are currently available. Typically they have 4k or 5k LUTs wihich is a useful middle ground, not so large as to be expensive or encourage wasteful inefficient implementation ( :)), not so small that you'll be fighting to find enough LUTs to do more than implement relatively trivial logic.

An upside for those who care is that the iCE40 range has a completely open source toolchain available for it. I have no philosophical axe to grind on that front, but the availability of a toolchain that is all command line orientated rather than GUI oriented better suits my way of working, and may better suit other folks of a similar bent.
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Offline dorkshoei

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Re: Absolute bare minimum FPGA thats breadboardable?
« Reply #24 on: January 12, 2022, 06:48:54 pm »
An upside for those who care is that the iCE40 range has a completely open source toolchain available for it. I have no philosophical axe to grind on that front, but the availability of a toolchain that is all command line orientated rather than GUI oriented better suits my way of working, and may better suit other folks of a similar bent.

Toolchains are an important part.  @rstofer raised this above.

I know when I started the board I was working even though still available had already been obsoleted in the current Xilinx sw offering and I had to download an old version and that had issues wrt Windows 10.    Sometimes even though it's less polished opensource has advantages (if you like to use the cmdline,  or want better legacy support).

The next board I bought was an IceBreaker due to the opensource toolchain.      I did just get an ARTY S7 but only because someone was selling it here for $30.

It is definitely an important factor in leaning.   It might be the most important.
 


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