Very Cool Low-Power $5 FPGA Module

DIPSY is cute in an NE555 kind of way (my first 8-pin DIP :-) but I usually need a lot more than 5 I/Os for any useful FPGA project.  I'd much rather see a QFN or small TQFP brought out to 50 mil centers as a prototype-friendly module.  If it could be plugged into a 44- or 68-pin PLCC socket that would be even better.  That's probably not possible for $5.

It would be cute to do a 555 emulator using DIPSY, with one-shot and astable functions programmed in.  Not very useful, but cute.

I don't know if IceStorm is planning on supporting any Lattice chips other than HX1K.  I'd rather use the free-as-in-freedom IceStorm than Lattice's free-as-in-beer proprietary software.

@betajet: It would be cute to do a 555 emulator using DIPSY...

I can't remember how many 555-based projects I built as a lad ... but then, of course, I can't remember what I had for breakfast today LOL

I agree the pincount is small, but modern FPGA/CPLD packages are getting so small that having something to throw on a breadboard would be a welcome relief - and maybe the next step would be a 24 pin version.  But I'm with you on the PLCC module - put a small microcontroller alongside the FPGA and land both on a pcb that drops into a 44 pin PLCC and you would have a great platform for building an embedded controller with custom microcontroller peripherals.

One neat thing, if you are into this kind of things, is that there's a purely Open Source toolchain for Lattice ice40 FPGAs. Apparently it is quite fast

http://www.clifford.at/icestorm/

Why would one care? well, for one thing, because it is portable and small, it is possible to put the toolchain on the embedded device and compile and change the FPGA configurations on the fly.

Would a cheap device like this be a good educational tool for someone who wanted to learn or teach FPGAs?

What would be a good series of texts to read while doing so?

@perl_geek: What would be a good series of texts to read while doing so?

I'll ask Antti to comment

I've been using IceStorm for a couple days now and it's terrific.  See my 'blog and comments here: IceStorm: Reverse-Engineering the Lattice iCE40 Bitstream

I believe the current version of IceStorm only supports the iCE40-HX1K.  I don't know if it does DIPSY's iCE40-UL1K.  However, the differences are probably minor and IceStorm's author would be likely to support the chip if DIPSY is mass-produced. 

perl_geek asked:  Would a cheap device like this be a good educational tool for someone who wanted to learn or teach FPGAs?  What would be a good series of texts to read while doing so?

Personally, I like the Lattice iCEstick which costs US$21-25 and plugs into a USB A port.  It uses an FTDI FT2232H to program its iCE40-HX1K, which is similar to DIPSY's part and has 144 pins.  iCEstick has five LEDs, a Digilent Pmod connector, and two rows of 10 holes on 0.1" centers for user I/Os.  It's more expensive than DIPSY, but it's available now and has a built-in programmer.

iCEstick is directly supported by the free-as-in-freedom open-source IceStorm Project. 

I don't have any personal experience with FPGA texts for the beginner, but the Front de Libération des FPGA (FPGA Liberation Front) has favorable reviews (in French) of FPGA Prototyping By Verilog Examples and FPGA Prototyping By VHDL Examples, both by Pong Chu and both for Xilinx Spartan-3.

There is also the iCEblink40 evaluation kit, available with either the LP1K or HX1K device, for U$39.39 at DigiKey.
One interesting feature is that it supports 3.3V Arduino Shield boards, as well as other expansion boards, by providing 63 3.3V digital I/O pins on 0.1" thru-hole connections.

Hi I have been involved with open source bitstream level stuff also!

I had under NDA bitstream info for AT40K, also used in FPSLIC and I have done some bitstream RE. I talked to author of icestorm, he did give permission to link to his site from my project, I did not ask about support for ice ultra, but as ice as such is already supported adding ice ultra is not a problem at all, if there is interest or someone with free time. I will have to develop some bitrstream manipulation tools for DIPSY anyway, so I can also peek in into icestorm to see what is needed to add new device support there.

@betajet: Personally, I like the Lattice iCEstick...

I like that one too -- I like its Pmod interface that lets you connect a load of different Pmod sensors and suchlike.

openchip wrote: Hi I have been involved with open source bitstream level stuff also!

Since you know a lot about taming bitstreams, I'd be interested in your opinion of what open bitstream documentation and/or software is available for Xilinx Spartan-6 and/or Spartan-3.  I found out recently about Wolfgang Spraul's fpgatools, but I've heard it's dormant and incomplete at this time.  There's From the Bitstream to the Netlist by Jean-Baptiste Note and Éric Rannaud, but that's more a how-to-do-it and I don't think their software is available any more.  There's also Flavia: the Free Logic Array but it only programs LUTs and flip-flops, and doesn't attempt to reverse-engineer Spartan-3 or Spartan-6 routing.  (Flavia's author is in the USA and is nervous about exposing too much.)

There are probably other efforts I don't know about, and some of them might be published.

Flavia seems to be just a re-incarnation of "meta-FPGA" except it is is "meta-PLD".

http://florianbenz.github.io/bil/index.html

This seems also be abondoned, I have the sources and I have recompiled them, for some reason. BIL did with almost no changes at least partially "eat" 7 Series bitstreams too.

A lot of information is available as part of the Xilinx partial reconfiguration flow, but this is of course protected with licensing/legal stuff and is not freely available except a few universities.

There is nothing impossible with bitstream RE, but there should be a good reason for this. ICE is really a good choice and candidate for free flow. The bleeding edge FPGAs from A (intel?) and X are not.

It seems that all free fpga tool projects, die, for reason not disclosed.

ICEblink40 kits are of course not bad value for the price. Well I must say I am biased here: ICEblink kits do not use FT2232H based USB interface, but from some legacy reason are based on the overleft adept support originating from the Silicon Blue iceMAN65 kit. For iceMAN65 I never got the adept stuff to work, and ended up writing my own tools to program the spi flash for ICE65. So I would prefer any ICE kit-board with FT2232H based interface. All lattice tools do support FTDI based "simple" interfaces, Digilent (now owned by NI) Adept (uses ATUSB162 or ATUSB82), my bet is that NI has little interest to support Lattice development tools. Lattice did get the "adept" deal as legacy from Silicon Blue, in newer ICE boards it is replaced with on-board FTDI solution, except the ICEblink40. As said I am biased on this topic. ICEstick, ICEultralitebreakout and ICEultrabreakout board all do use FTDI solution.

Thank you for the references to MPGA and BIL.  Perhaps the reason free-as-in-freedom FPGA projects in the past have died is that not enough people found out about them.  I wasn't familiar with either MPGA or BIL, and I've wanted open FPGA documentation for decades.

I think IceStorm will be different, since its documentation is mostly complete and the iCE40 architecture is simple enough that one can write good tools.  Also, free-as-in-freedom software is a lot more accepted nowadays.  It's not just for hippies any more :-)

The Altera MAX10 is also a nice choice although you have to use Altera's software... The Arrow BeMicro MAX 10 Evaluation Kit is $30 and looks to be useful. I'd like to have one but realisitically don't have time to play with it...

Adafruit has a nice FTDI FT232H Breakout Board for US$15.  This is a single-port version of the FT2232H.  I'm going to have to try it out with my iCEblink40 HX1K one of these days.  I got the iCEblink several years ago when they were on sale for $19, but never had time to download the Lattice software or read its EULA :-)

You most likely do not need and probably can not use the FTDI breakout board with iceblink40, I think the on-board adept circuitry will also work for you. SPI pins are on header, so theretically you can connect external programmer, but I do not know if the ATmega on board releases the spi pins and reset when it has no usb connection.

openchip said:  I do not know if the ATmega on board releases the spi pins and reset when it has no usb connection.

I'm pretty sure I can just short the ATmega reset to ground and it will release the SPI pins.  One nice thing about iCEblink is that it has 0.1" headers for most signals.  I do need to find a convenient pin for iCE40's CDONE and wire to it.

The problem with using the Adept circuitry is that I don't know what communications protocol is implemented on the ATmega.  I'd rather just wire up my Adafruit FT232H Breakout Board so I can use IceStorm's iceprog out of the box, or use my own FTDI software.

Rush order for REV 1 PCBs placed and confirmed to arrive on 21 july. This is not a final PCB design, but we had hard deadline to get the boards in the morning of 21st because of some one coming to visit us. More infos later.

Besides the 44-pin and 68-pin PLCCs, there is also an 84-pin PLCC. I see that PLCC sockets contact the edge of the PLCC. How would one make the edge contacts on a PCB module to plug into a PLCC socket? Can one get sufficiently-accurate edge dimensions in a PCB? The apparently-obsolete CLCC would have been perfect for a PCB module, as CLCC contacts are on the face, not the edge. Digi-Key lists only one CLCC socket, for 68 pins, for $17, too expensive.

I'm not sure how you'd make contacts on the edge of a PCB. I suspect it would be expensive though...

Maybe a better idea would be to do a larger DIP size. That could easily be done just expanding what they're doing now and for probably not much more cost.

traneus asked: How would one make the edge contacts on a PCB module to plug into a PLCC socket?

The Japanese company HuMANDATA LTD does it: http://www2.hdl.co.jp/en/index.php/plcc68-series.html

It's not clear how the PLCC pins are attached to the edge of the PCB.  HuMANDATA modules are expensive.

Update :  Ironwood Electronics has a number of PLCC adapters, and you can get a "PLCC SMT Foot" that solders onto the bottom of a PCB and plugs into a PLCC socket.  Ironwood uses them as a component of their own adapters, but you can get the feet as a separate item.  Here are the 68- and 84-pin versions.

http://www.ironwoodelectronics.com/catalog/Content/Drawings/SF-PLCC68-J-S-01Dwg.pdf

http://www.ironwoodelectronics.com/catalog/Content/Drawings/SF-PLCC84-J-S-01Dwg.pdf

Unfortunately, they're very expensive too.

I suppose you could get an empty PLCC package and dead-bug solder a chip-scale package to it.  That would make the other solutions seem cheaper.

I have been the PLCC68 path many times. The socket adapters are high quality, but rather expensive. Doing it with PCB technology alone, could maybe be cheaper, but it does require a lot of routing with small sie router bit. I should maybe talk once more with my favorite PCB fab. What they can do is pretty cool, the DIPSY PCB's have under the FPGA 50 micron track and space as example. I was not sure they can do that until I got the PCBs.