Introducing the PiXi Add-on board


25 posts
by MrMarkus » Mon Nov 05, 2012 11:03 pm
Hi,

I'd like to open up a discussion on a board that i'm working on that I hope may be of interest to others out here. It's called the PiXi Board because its main component is a user programmable Xilinx FPGA.

I started to develop the board partly for my own project which is slow-scan astronomical camera. But after seeing some calls for additional GPIO functions on the Pi, i've modified the design to hopefully make it of interest to a wider audience. I have a fairly basic website that i'm working on that is very much work-in-progress but it is live and has all of the latest information on the development of this board. http://www.astro-designs.com/page14.php

The board designed to be a low-cost plug-on board that sits on top of the Pi, connecting to the Pi through its P1 connector (& P5 connector on the Rev 2, if it's fitted on the top of the board) to provide the following:

Up to 56 GPIO including 24 x 3.3v CMOS I/O, 16 x 5v CMOS I/O & 16 x open-collector outputs;

Interfaces to the Raspberry Pi via I2C, SPI & GPIO (uses both P1 & P5 connectors on the Rev 2, although P5 does not need to be fitted);

8 on-board LEDs;
4 on-board push-button switches;
RS232 serial port;
1k EEPROM provides non-volatile storage;
33MHz clock;
Ability to interface directly to a LCD or vacuum florescent display;
Ability to interface directly to up to 8 radio-control style servos or speed controllers;
User programmable 200,000 gate FPGA (XC3S200A);
4-channel analogue to digital converter;
4-channel digital to analogue converter;
3-Axis accelerometer;
3-Axis magnetometer;

A 2.5mm power connector for optional external 5V power supply (it can be powered from the 5v supply from the Pi if the Pi's 5V power supply is powerful enough). This can also be used to provide power to the Pi itself if the user is not using the USB connector on the Pi to provide the power;

An edge connector provides further expansion capabilities over 10 differential or 20 single-ended signalling;

The user can use freely available software tools available from the manufacturers of the FPGA to create their own designs to run on the FPGA;

No expensive programming hardware is needed, the PiXi will be provided with software to allow the Raspberry Pi to reprogram the FPGA through the GPIO on the Pi's 'P1' connector;

Re-design the I/O to your own requirements or protocol using either SPI, I2C and/or basic GPIO from the Pi. All interfaces on the P1 connector can be passed to the PiXi GPIO so that if any interface is not being used on the PiXi then it can be used off-board on other hardware;

Optional location for a 2mm 2x7 SMT header to allow the user to connect to a standard Xilinx programming & debug tool (if you have one). Please note that the Xilinx programming & debug tool would not be provided;

Example FPGA designs will be made available to link your Raspberry Pi to all features on the PiXi Board so that you can use them immediately. The FPGA can be entirely designed by the user or the user can use an example design that will be provided;

I'm tentatively working towards a target price of £35. For this the user would get the fully assembled board, some example FPGA designs, software to run on the Pi to load the FPGA and some example software.

The board is currently in the final stages of design and I hope to get some prototypes back in a few weeks time. While I can't sell any at present, i'd very much welcome any feedback anyone has on whether such a product would be of interest to many people here. So please let me have your thoughts

Thanks & kind regards,
Mark
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by pygmy_giant » Mon Nov 05, 2012 11:19 pm
Cool ... seems like its aimed at quadcopter type applications ... what sort of things do you imagine it being used for? Is it an expansion board or would it require the Pi to program and then run autonamously afterwards? Would replacing the 1K EEPROM with a 512K EEPROM cost much more or cause problems?
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by MrMarkus » Tue Nov 06, 2012 9:02 am
pygmy_giant wrote:Cool ... seems like its aimed at quadcopter type applications ... what sort of things do you imagine it being used for? Is it an expansion board or would it require the Pi to program and then run autonamously afterwards? Would replacing the 1K EEPROM with a 512K EEPROM cost much more or cause problems?


Thanks for your reply

The main feature with this board is the 200,000 FPGA which gives the user the ability to experiment with digital electronics or even use it for product development. Couple a low cost processor, in this case the Raspberry Pi, with a low cost small-medium sized programmable logic function and it could open the doors to more advanced applications while keeping the development costs very small.

It gives the user the chance to learn a new skill - VHDL or Verilog are industry standard languages and fairly easy to get to grips with, especially if you know some software.

I didn't really have an application in mind when I designed this - apart from my own 'AstroCam' project (which has been on the cards for about 10 years...), so I tried to put a few things on the board that would create some interest.

If this worked as a product then I'd love to see it appear in schools, colleges or universities alongside a few Rasberry Pi's as a tool for learning digital electronics and/or VHDL / Verilog. Hense why i'm trying to keep the price as low as possible.

It does need the Pi to load the configuration into FPGA on power-on / boot. It's a volatile component so it loses it's configuration when there's no power but it only takes a few seconds to configure it.

As for the question on the EEPROM, there is room for expansion, a larger device like a 512kbit part, could be fitted for around £1 extra, possibly less. I'm trying to keep the costs down to an absolute minimum so i've defaulted to a fairly small part but with a little surface mount soldering the user could replace the 8-pin chip with a larger capacity component. If there's significant call for a larger part then we could default to a larger part.

Thanks,

Mark
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by johnbeetem » Tue Nov 06, 2012 3:53 pm
You might consider adding an SPI Flash programming option so that the board doesn't have to be downloaded from RasPi or a JTAG cable on each use. This allows your board to be a custom interface board once FPGA development is complete. I believe SPI Flash chips are available in SOIC packages so they're easy to add later.
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by MrMarkus » Tue Nov 06, 2012 7:49 pm
Hi John,

I opted out of the SPI flash configuration option - or any configuration option that put the storage on the PiXi board, for two main reasons. Firstly cost but secondly because through force of habit (in my day job) I tend to opt to use a local processor to configure an FPGA because in 9 times out of ten there's a processor somewhere in the product, in this case it's the Pi.

The PiXi board is designed to accompany the Pi so the processor is always there to configure the FPGA so there's never any need for a separate configuration storage. I'm short of board space too so by using the processor to configure the FPGA it was one less component to fit.

There is always the option to fit the XC3S200AN instead of the 200A, the 'AN' part offers non-volatile storage and is pin compatible but it's more costly. But it's always an option...

Just a quick comment on the JTAG connector, please note that it's not normally fitted as most people using the Xilinx Webpack tools for this board probably wouldn't have the Xilinx JTAG programming tool. So again it came down to cost and I decided not to include the JTAG connector in the parts list. But the location is there on the board for anyone who wants to fit one.

Best regards,

Mark
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by bswiec » Tue Nov 06, 2012 10:48 pm
Hey Mark,

Out of curiosity, is there a reason you went with the older Spartan 3 device instead of, say, xc6slx9 for a similar price point? Has more resources/performance (including DSP slices and hard memory controller).

Packaging issue?
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by pygmy_giant » Tue Nov 06, 2012 10:54 pm
Also have you considered using the IvanSense MPU-6050 and AK8975 ?
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by MrMarkus » Wed Nov 07, 2012 4:56 pm
bswiec wrote:Hey Mark,

Out of curiosity, is there a reason you went with the older Spartan 3 device instead of, say, xc6slx9 for a similar price point? Has more resources/performance (including DSP slices and hard memory controller).

Packaging issue?


Hi. The reason was cost, I got a better price from Xilinx on the XC3S200A than the XC6SLX9. Well... it was when I started... they later came back with a closer price (still more expensive) but I was too far down to change so I stuck with the S3. I'd agree with you that the S6 is a better choice but 'cheaper' won the battle for now... The S6 is available in the same package so apart from some re-routing it shouldn't be too much effort to change it at a later date. Right now I'm fighting to keep the cost down so every peny saved give me a chance to put this into production.

Cheers,

Mark
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by MrMarkus » Wed Nov 07, 2012 4:58 pm
pygmy_giant wrote:Also have you considered using the IvanSense MPU-6050 and AK8975 ?


I haven't... But then I have years & years worth of experience with Xilinx & Altera FPGAs and haven't even heard of the IvanSense part or AK8975 so I went with what I know best. You can do anything with a Xilinx anyway... :D
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by MrMarkus » Sat Nov 24, 2012 9:12 pm
Hi All,

Just a quick post to highlight the latest news on the PiXi-200 http://www.astro-designs.com/page8.php. As of 22nd November, the design is complete and we've submitted the design to get the first prototypes manufactured, so we're making progress...

We're a little behind where we'd hoped we'd be by now and with Christmas comming up we're not likely to get the finished product back until some time in January. But there's plenty to do before then... I hope to be able to post some pictures of the space-model within the next 2-3 weeks plus I'm putting together a basic user-manual and cleaning up the schematics for release too.

All for now,

Best regards,

Mark
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by meltwater » Tue Nov 27, 2012 10:29 am
Looks like a great project, interesting to see what stuff can be produced on the FPGA.
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by MrMarkus » Wed Dec 19, 2012 12:12 am
Hello All!

The PiXi-200 project is moving forward. I recently took delivery of a sample of the bare PCBs so I took the opportunity to pop a few connectors on one of them and take some pictures to help illustrate what it'll look like and how it connects to the Pi.

If you're interested in looking at a partially assembled PiXi, please have a look at the latest PiXi-200 news page (http://www.astro-designs.com/news.php?category=2) and towards the bottom of the PiXi-200 project page (http://www.astro-designs.com/page14.php) to view the pictures.

Thanks & kind regards,

Mark
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by johnbeetem » Wed Dec 19, 2012 3:03 am
MrMarkus wrote:The PiXi-200 project is moving forward. I recently took delivery of a sample of the bare PCBs so I took the opportunity to pop a few connectors on one of them and take some pictures to help illustrate what it'll look like and how it connects to the Pi.

Very nice! I'm glad to see you're making progress.
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by MrMarkus » Sat Dec 22, 2012 8:50 am
Latest update...

Woohoo! - Christmas came early and the boards arrived early yesterday as hoped. So far it looks good. The Pi can program the FPGA, the lights flash, switches work... basic stuff but it'll be a little while before I've tested everything.

Anyway, I'll update the pictures on the website next and get on with testing the rest of the board - in between finishing off the Christmas shopping of course...

All for now, next update will probably be after Christmas, so have a Merry Christmas all!

Best regards,

Mark
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by NinjaJoe » Sun Jan 06, 2013 3:54 pm
MrMarkus wrote:Latest update...

Woohoo! - Christmas came early and the boards arrived early yesterday as hoped. So far it looks good. The Pi can program the FPGA, the lights flash, switches work... basic stuff but it'll be a little while before I've tested everything.

Anyway, I'll update the pictures on the website next and get on with testing the rest of the board - in between finishing off the Christmas shopping of course...

All for now, next update will probably be after Christmas, so have a Merry Christmas all!

Best regards,

Mark


Thumbs Up! :D will keep update on your progress.. looking forward to buy one of these!
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by adecold » Mon Jan 28, 2013 4:44 am
This is an awesome project. Keep up the good work
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by MrMarkus » Fri Jul 26, 2013 4:17 pm
It's been a while since I last posted so I thought it was about time for an update...

There's a full post at www.astro-designs.com/news.php but here's a clip of the more interesting bits:

We've been busy on and off over the last few months looking at improving the design,here's a quick run through the changes & improvements:

1) Wider input supply range from 6.5 to 15V using a built-in efficient 5V regulator as standard. The ability of the PiXi-200 to supply power to the Raspberry Pi and for the Raspberry Pi to provide the 5V power to the PiXi-200 remains in place;
2) The GPIO2 header has been changed so that it's better suited for connecting to eight radio control or 'hobby' servos plus it now has the option to drive up to four additional servos using the eight high-current open collector drivers to provide four extra servo ports;
3) The 100-way 'Expansion Connector' changed from the edge-connector to a 50-way 2mm header to make this more readily accessible for the majority of users. The functions on this interface remain the same and the connector can still potentially be used for data rates of up to 500Mbps;
4) An SPI flash has been added to configure the FPGA very quickly, prior to the Raspberry Pi booting. The option to program the FPGA directly at boot-up using the Pi has been retained for flexibility. The addition of the SPI flash also allows the product to be used stand-alone;
5) The MMA7660 3-axis accelerometer and MAG3110 magnetometer have been replaced with an InvenSense MPU-9150. This integrates a 3-axis accelerometer and a 3-axis magnetometer within a single package, plus it adds a 3 axis gyroscope;
6) The surface mount connectors have been replaced with through-hole versions so that the board is more rugged;
7) Power supply pins have been added to the GPIO1, GPIO2 & Analogue connectors so that the user has the option to power any accessories or add-ons through these connectors;
8) The number of ADC channels has been increased to 8;
9) GPIO3 will no longer be limited to being configured in banks of 8, all 16 I/Os will be individually configurable for input or output if required. Furthermore, the I/O voltage can be set to either 5V or 3.3V.
10) Introduction of an Arduino-compatible shield interface so that the PiXi-200 can now interface to a number of the 3.3v or 5v Arduino-compatible 'shields' already out there.

The introduction of the Arduino-compatible shield support has led to a slight increase of the overall board length by approximately 22mm. The width is now exactly the same as the Raspberry Pi.

So what's next...

Well, we've obviously got to get the next version built and tested and we're pushing this as hard as we can to get it done quickly. However, given the potential volumes involved, we're spending some time making sure that this stands every chance of being 100% correct in terms of design for performance, design for reliability and design for manufacture. With this in mind, please don't be too put-off when we tell you that we hope to have the first boards back in our hands for testing around the beginning of September.

Once we have the boards in our hands and we've got some pictures of the first boards and videos of the boards in action we'll then work towards launching the product for general availability.

So please don't give up hope if you're interested in getting your hands one one of these, it's getting quite exciting now and we're just as enthusiastic as ever about getting this product into market.

More news soon...

Kind regards,

Mark
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by elektrknight » Sat Jul 27, 2013 4:57 am
So please don't give up hope if you're interested in getting your hands one one of these,

Just "discovered" your board and I want the new one! Do you ship across the pond?
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by MrMarkus » Sat Jul 27, 2013 6:53 am
Just "discovered" your board and I want the new one! Do you ship across the pond?


That's the plan, we've had interest in the PiXi-200 from all around the world so we'd very much like to be able to support that interest and ship world-wide.

Regards,

Mark
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by MrMarkus » Fri Mar 28, 2014 12:14 pm
It's been a while since I last posted, ok it's been a very long time... so I thought it was about time for a quick update on the development of the PiXi add-on board.

Firstly, it's still going strong, despite a huge delay while we gathered our thoughts, not to mention having to work on the day-job which frequently and somewhat frustratingly gets in the way... but it's nearing completion. More importantly, it's nearing the time where we'll be launching our Kickstarter project, at which point you'll be able to get your hands on one!

Please take a look at the product pages on the Astro Designs website (http://www.astro-designs.com/pixi-200.html) for the latest information, specification, pictures and application notes.

We're currently waiting for pricing for the assembly of the next round of prototypes following the completion of the design for the second revision. Once we have these we'll be placing orders to build up to 100 units, some of which will be given away to the general public. To be in with a chance of winning one, simply follow us on twitter (http://twitter.com/AstroDesignsLtd) or email us at pixi@astro-designs.com. Once we have the next round of prototypes, apart from testing them and integrating them into some of our own projects, we'll also be lauching our Kickstarter project.

To help show how the PiXi add-on board can be used in education we'll be offering a reward on Kickstarter that include the "PiXi Expermienter" board. This will allow the user to imediately experiment with most of the functions on the PiXi add-on board, promoting the PiXi as a low-cost platform for learning about FPGA technology, VHDL & Verliog hardware definition languages. There's a diagram of the PiXi Experimenter on the gallery (http://www.astro-designs.com/pixi-200_gallery.html) and you can download the draft application note that describes it in a little more detail on the application notes page (http://www.astro-designs.com/pixi-200_appnotes.html)

We would love to hear any thoughts that anyone might have on the PiXi Experimenter - would you like to see anything else on it, is there anything we can remove to keep the cost down, too much? too little?... It's a concept at the moment so there's plenty of time to make some changes, so please feel free to comment.

Many thanks,

Mark
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by MrMarkus » Tue Apr 15, 2014 12:58 pm
The schematics for the original prototype PiXi-200 (1.1) have been released and can be downloaded from either GitHub (https://github.com/astro-designs/pixi-200/tree/master/board) or http://www.astro-designs.com/downloads_pixi.html.

There are also Autocad compatible files for the mechanical design of the PiXi 2.0 which include a reasonably accurate model for the Raspberry Pi that we put together.

Enjoy :)

Mark
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by MrMarkus » Tue Apr 22, 2014 1:09 pm
Something we did a little while ago was to try to demonstrate how the PiXi could be used to control a Lego robot that used Lego Mindstorm NXT sensors & servos. We took such an example to the Oxford Raspberry Jam back in February but only recently got around to creating a quick YouTube video and documenting some of it. You can see a quick video demonstration on YouTube here: https://www.youtube.com/watch?v=4rwRSgO6mbs plus we created a quick schematic that shows something of the design of the interface board that plugs on to the top of the PiXi in the demonstration which can be found at http://www.astro-designs.com/downloads_pixi.html. There's a more detailed description of the example here: http://www.astro-designs.com/pixi_project_33.html

Enjoy! :)
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by MrMarkus » Mon May 12, 2014 12:54 pm
Here's another random example of what can be done with the PiXi add-on...

http://www.astro-designs.com/pixi_project_15.html

Enjoy :)

Mark
PS 15 days and counting - until the next stage PiXi 2.0 arrives...
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by MrMarkus » Mon May 12, 2014 12:57 pm
Nearly forgot - if you're near Oxford (UK) and can get to the Oxford Raspberry Jam on the 15th May, one lucky attendee will win a PiXi (once they're in and tested...)

http://www.eventbrite.co.uk/e/oxford-raspberry-jam-may-15th-2014-tickets-11443322285?aff=eorg

Kind regards,

Mark
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by MrMarkus » Mon Jun 02, 2014 7:59 am
It's taken a while (as you can see from when this topic first started...) but we're pleased to announce that the latest version of the PiXi (2.0) is finally here!

http://www.astro-designs.com/pixi-200_gallery.html

Following our raffle at the Oxford Raspberry Jam earlier in May (http://raspberryjam.org.uk/oxford/show-and-tells/show-and-tell-may-2014/), we can also announce that Dave P. is the winner of the first PiXi 2.0 - well done Dave!

Please follow us on Twitter to help spread the word about this project (http://www.twitter.com/astrodesignsltd) if you do follow us (or drop us an email to pixi@astro-designs.com) then you'll automatically be entered into a draw to win one of two more PiXi (2.0) boards up for grabs!

So what's next... testing. It's looking good so far, but a week of intense testing awaits...

Thanks,

Mark
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