Cheap Xilinx LX9 Starter Board

for bbc micro/electron hardware, peripherals & programming issues (NOT emulators!)
User avatar
hoglet
Posts: 8529
Joined: Sat Oct 13, 2012 6:21 pm
Location: Bristol
Contact:

Cheap Xilinx LX9 Starter Board

Post by hoglet » Tue Oct 27, 2015 7:47 pm

Hi Guys,

Just noticed this on eBay:
http://www.ebay.co.uk/itm/XC6SLX9-Start ... 1687888503
Cheap_LX9.JPG
Features:
  • Based on Xilinx Spartan 6 FPGA XC6SLX9
  • On-board 50MHz oscillator
  • +3.3V LDO for IO supply
  • 4-digit seven segment dislay
  • RS232 interface
  • 12-bit VGA dispay
  • PS2 interface for keyboard
  • Eight blinky LEDs
  • Three pushbuttons
  • One 8-bit DIP switch
  • Two Pmod compatible headers for low speed Pmod modules
  • One 30-Pin headers,with +5V,+3.3V and 26 GPIOs Breakout( Pin numbers are clearly marked on PCB )
  • 14-pin header for JTAG configuration
  • Configuration device : W25Q64BV
  • One reset button for device reconfiguration
  • 5V power supply( 500mA PTC fuse protected )
  • PCB Size : 10cm*10cm
Seems very good value for money at £22 :shock: so I've ordered one to try out.

The only thing it's missing is an SD Card slot, but this could easily be added externally.

Dave

User avatar
BigEd
Posts: 2609
Joined: Sun Jan 24, 2010 10:24 am
Location: West
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by BigEd » Tue Oct 27, 2015 8:32 pm

That would have "just" the 64k of on-chip memory? Should be enough for many 8-bit purposes!
(You can squeeze a little more memory out of the random logic)

User avatar
hoglet
Posts: 8529
Joined: Sat Oct 13, 2012 6:21 pm
Location: Bristol
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by hoglet » Tue Oct 27, 2015 9:04 pm

Hi Ed,
BigEd wrote:That would have "just" the 64k of on-chip memory? Should be enough for many 8-bit purposes!
(You can squeeze a little more memory out of the random logic)
Yes, I agree it will be tight for many of things.

But I've had an Atom FPGA working on a vanilla Papilio, which has only 40K of on-chip memory.

Some more options.....

Moving up from this, most cheap FPGA boards with memory use DRAM. For example, the Numato Mimas V2 is nice and is $50:
http://numato.com/fpga-boards/xilinx/sp ... sdram.html
Mimas_V2_FPGA_Board_Large.jpg
But this uses DDR SDRAM, which is much harder to use (but not impossible....)

The cheapest board that includes SRAM is the Flea FPGA board, which is $65:
http://www.fleasystems.com/fleaFPGA.html
Flea_FPGAjpg.jpg
But this uses a lattice FPGA, and I have no experience of that or it's tool chain.

Edit: There's also a new Flea FPGA Uno which is $50 and has SRAM: http://www.fleasystems.com/fleaFPGA_Uno.html

The only Xilinx board I know of with SRAM is the Papilio Duo. And that costs $88 for the FPGA board and $35 for the Classic Computing Shield and $15 shipping, which is £90 (i.e. more than 4x as much :shock: )
PapilioDuo.jpg
CC-Shield.jpg
Here's an up to date comparison of cheap boards:
https://joelw.id.au/FPGA/CheapFPGADevelopmentBoards

Dave

User avatar
BigEd
Posts: 2609
Joined: Sun Jan 24, 2010 10:24 am
Location: West
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by BigEd » Tue Oct 27, 2015 9:31 pm

Thanks for the info and especially for that comparison link - the one I had at
http://forum.6502.org/viewtopic.php?f=10&t=1787
had become quite outdated. (Edit: although it does seem that I'd already noted the link at the end of the thread!)

With 26 GPIOs, it should be possible to hook up an external bytewide SRAM, at least 128k and maybe bigger. (Especially if you also used an address latch.)

User avatar
hoglet
Posts: 8529
Joined: Sat Oct 13, 2012 6:21 pm
Location: Bristol
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by hoglet » Sun Nov 01, 2015 9:44 am

Here's another one, sold on the Hackaday store for $69.97:
http://store.hackaday.com/products/ardu ... pga-shield
hackaday_fpga.jpg
- LX9 FPGA
- 128Kx16 async SRAM

Dave

poink
Posts: 963
Joined: Tue Mar 01, 2011 10:27 am
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by poink » Sun Nov 01, 2015 1:52 pm

I picked up an Altera based board to play around with a bit ago. Not had a great deal of time to play with it, unfortunately.

It seems to have a reasonable selection of onboard devices (DDR RAM, ADC, VGA, PS/2 etc) and I *think* there's JTAG onboard (although, you do pay for that convenience in terms of the spec of the FPGA - it's a 6K Cyclone IV)

User avatar
hoglet
Posts: 8529
Joined: Sat Oct 13, 2012 6:21 pm
Location: Bristol
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by hoglet » Sun Nov 01, 2015 2:10 pm

poink wrote:I picked up an Altera based board to play around with a bit ago. Not had a great deal of time to play with it, unfortunately.

It seems to have a reasonable selection of onboard devices (DDR RAM, ADC, VGA, PS/2 etc) and I *think* there's JTAG onboard (although, you do pay for that convenience in terms of the spec of the FPGA - it's a 6K Cyclone IV)
Do you have any links to specifications or manuals? This looks quite interesting.

derekw
Posts: 6
Joined: Fri Nov 14, 2014 11:39 am
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by derekw » Sun Nov 01, 2015 10:35 pm

Another board for the list. This is a less complex XC6SLX9 Spartan board with limited peripherals (LEDs, buttons and USB) but with 72 GPIO pins.
picture.JPG
It's programmed via JTAG so some additional cost involved but at just over £20, it's not bad value. I've added 512Kx8 50ns SRAM, SD Card, 9 bit VGA, PS2 keyboard and audio out allowing it to run Dave's Electron and Atom fpga implementations. The added peripherals would probably cost around between £10 - £15 although all but the memory came from other projects.

Derek

User avatar
hoglet
Posts: 8529
Joined: Sat Oct 13, 2012 6:21 pm
Location: Bristol
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by hoglet » Sun Nov 01, 2015 10:44 pm

derekw wrote:It's programmed via JTAG so some additional cost involved but at just over £20, it's not bad value. I've added 512Kx8 50ns SRAM, SD Card, 9 bit VGA, PS2 keyboard and audio out allowing it to run Dave's Electron and Atom fpga implementations. The added peripherals would probably cost around between £10 - £15 although all but the memory came from other projects.
Ooooh, nice! Can you post a piccie of what you ended up with as a "wing"?

Dave

derekw
Posts: 6
Joined: Fri Nov 14, 2014 11:39 am
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by derekw » Sun Nov 01, 2015 11:27 pm

Describing them as "wings" would be a bit extreme. One is a memory board with some extra pins for a digital joystick. The other is really a miniature motherboard into which plugs the VGA/PS2 board, SD card and audio output. There are also some additional pins for configuration such as controlling multiboot at some later stage. When I've some time and and I've finalised what additional peripherals to put on, I will produce a wing - I was thinking of including some parallel flash memory to save loading roms from spi and also, very tentatively, rather than use multiboot, include an Arduino Pro to load from an SD card or PC via JTAG amongst other uses.

Anyway, some quick pictures below and as you'll see, very much a hacked prototype.

Derek
IMG1.jpg
IMG2.jpg
IMG3.jpg

User avatar
flynnjs
Posts: 825
Joined: Tue Jul 06, 2010 9:33 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by flynnjs » Mon Nov 02, 2015 12:15 am

That is from the same ebay seller as the orginal board that kicked off this thread.
It looks suspiciously like the same pinout and size as a DE0-nano.

poink
Posts: 963
Joined: Tue Mar 01, 2011 10:27 am
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by poink » Mon Nov 02, 2015 10:42 am

hoglet wrote:Do you have any links to specifications or manuals? This looks quite interesting.
Best I've found seems to be in this survey of FPGA boards.

Documentation-wise, it's pretty basic. The supplied discs are mostly filled with general FPGA stuff ripped from Altera's website (all in Chinese). The only manual I'm aware of is the one page schematic. Having just read it, there's no on-board JTAG; although ByteBlaster clones are very cheap.
Attachments
schematic_v200.pdf
(138.33 KiB) Downloaded 72 times

User avatar
flynnjs
Posts: 825
Joined: Tue Jul 06, 2010 9:33 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by flynnjs » Tue Jan 12, 2016 6:01 pm

Just to follow up, I now have one of the cheap "eepizza" LX9 boards running in the CPU socket of my B.
Photos a bit later. Also, I can confirm it is the same pinout as the DE0-nano.

User avatar
flynnjs
Posts: 825
Joined: Tue Jul 06, 2010 9:33 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by flynnjs » Wed Jan 13, 2016 12:02 am

Here's my adapter board (left), cheap LX9 board (mid) and DE0-nano (right)
IMG_0807.JPG
Adapter board and LX9 sandwiched (left)
IMG_0808.JPG
Underside of adapter showing pins that fit in CPU socket and level shifters (left)
IMG_0810.JPG
Had this stuck in my B with Dave's ICE running and seems to run just fine.
At £20 it's a good modern and cost effective alternative to the GODIL 500.

J

User avatar
danielj
Posts: 7497
Joined: Thu Oct 02, 2008 4:51 pm
Location: Manchester
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by danielj » Wed Jan 13, 2016 6:29 am

=D> Jason, where did you find the adapter board? I've been searching and drawing a blank?

d.

User avatar
flynnjs
Posts: 825
Joined: Tue Jul 06, 2010 9:33 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by flynnjs » Wed Jan 13, 2016 7:58 pm

Homebrew. I've got 20 prototype boards but was going to re-spin and add some SRAM on the unused pins.

User avatar
BigEd
Posts: 2609
Joined: Sun Jan 24, 2010 10:24 am
Location: West
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by BigEd » Tue Jun 06, 2017 4:28 pm

Just wondering Jason, did you make any progress with your prototype? SRAM/40pin/LX9 is an attractive combination!

User avatar
myelin
Posts: 726
Joined: Tue Apr 26, 2016 9:17 pm
Location: Mountain View, CA, USA
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by myelin » Tue Jun 06, 2017 5:07 pm

hoglet wrote:Just noticed this on eBay:
http://www.ebay.co.uk/itm/XC6SLX9-Start ... 1687888503

Seems very good value for money at £22 :shock: so I've ordered one to try out.
Not bad, given that the XC6SLX9 costs $16 (£11) just by itself!
SW/EE from New Zealand, now in Mountain View, CA, making BBC/Electron hardware projects for fun.
Most interesting: Arcflash, FX2+PiTubeDirect Tube/Cartridge adapter, USB cart interface.

User avatar
flynnjs
Posts: 825
Joined: Tue Jul 06, 2010 9:33 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by flynnjs » Tue Jun 06, 2017 6:15 pm

More than £11 in small quantities... £11 plus VAT at least!

The adapter worked first time and I got Dave's ICE working on the LX9 so
as a minimum was an upgrade and cheaper than the GoDIL which is
Spartan 3 based.

As for the evolution, it's odd that you ask, because I'd not done anything
on it until last week. I'm not finished it yet but it is my main priority
right now.

User avatar
myelin
Posts: 726
Joined: Tue Apr 26, 2016 9:17 pm
Location: Mountain View, CA, USA
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by myelin » Fri Jun 09, 2017 7:05 pm

I just got my Scarab miniSpartan6+ (XC6SLX25 with micro-SD, 32MB SDRAM, 2 x HDMI, USB serial) adapter board up and running, so now I have a nice big FPGA hooked to my Electron's expansion connector. Working well; I got it to load Snapper off a block ROM last night. This should be a fun prototyping environment :)

Unfortunately I didn't consider the possibility of wanting to host a CPU on the 'outside' of the Electron when I designed this, but I've updated the design, and the next version should let me desolder my 6502 and emulate one in the FPGA, so I can test out my shadow RAM ideas.
SW/EE from New Zealand, now in Mountain View, CA, making BBC/Electron hardware projects for fun.
Most interesting: Arcflash, FX2+PiTubeDirect Tube/Cartridge adapter, USB cart interface.

bprosman
Posts: 333
Joined: Sun Mar 29, 2015 10:27 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by bprosman » Sun Sep 08, 2019 7:10 pm

I'm trying to figure out how Jason's level shifter board is working.
I do understand the working of this one :
http://www.ti.com/lit/ds/symlink/sn74cb3t16211.pdf
Bit puzzled though about the resistors used. Are they in series with the 5V DIL signals ?

//Edit, looks like its the same sort (connection) as used in the Godil

Kind regards, Bram
Last edited by bprosman on Sun Sep 08, 2019 7:24 pm, edited 1 time in total.

bprosman
Posts: 333
Joined: Sun Mar 29, 2015 10:27 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by bprosman » Mon Sep 09, 2019 10:24 am

Looking at Jason's level shifter board, it looks it is a copy of the level shifter part of the Godil, including the resistors and the same IC's.

@David - Hoglet
But weren't the resistors the parts that caused issues ? (like in the MPF-1?) What I understood from our previous discussions is that you choose the 74 series because they were more "hand solder-able", or did you have other reasons to do ?

Fully agree that they are a lot easier to solder, downside is that you have to choose on beforehand the data direction , so for an ICE-T65 you need a different board than for an ICE-T80, there Jasons (Godil's) solution seems more universal.

Giving it a 2nd thought , as it is only 38 signals max. One might even consider this one (or does that have downsides as well ?
Level_Shifter.jpg
Kind regards, Bram
Last edited by bprosman on Mon Sep 09, 2019 10:44 am, edited 1 time in total.

User avatar
hoglet
Posts: 8529
Joined: Sat Oct 13, 2012 6:21 pm
Location: Bristol
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by hoglet » Mon Sep 09, 2019 10:42 am

bprosman wrote:
Mon Sep 09, 2019 10:24 am
@David - Hoglet
But weren't the resistors the parts that caused issues ? (like in the MPF-1?) What I understood from our previous discussions is that you choose the 74 series because they were more "hand solder-able", or did you have other reasons to do ?

Fully agree that they are a lot easier to solder, downside is that you have to choose on beforehand the data direction , so for an ICE-T65 you need a different board than for an ICE-T80, there Jasons (Godil's) solution seems more universal.
The main reason I prefer the 74F "push-pull" level shifters is that GODIL's level shifters (with 1.5K pullups) do cause real problems on many systems:
- On the Beeb they cause the tube detection code in the MOS to fail (with a false positive).
- On the Spectrum, with the split data bus, they don't work well either

You could omit the 1.5K pullup resistors, but then the level shifter would only drive to a maximum of about 3.2V. This might not be high enough for some CMOS devices.

That's why I think on the long term it would be better to have dedicated 74F "push-pull" based adapters for each of the supported processors. My preferred device for these was the 74LVC4245, because these have dual supplies (5V and 3.3V). This means the 5V side can drive to ~4.5V levels.

Dave
Last edited by hoglet on Mon Sep 09, 2019 10:47 am, edited 3 times in total.

bprosman
Posts: 333
Joined: Sun Mar 29, 2015 10:27 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by bprosman » Mon Sep 09, 2019 10:45 am

Hi Dave,
is that GODIL's level shifters (with 1.5K pullups) do cause real problems on many systems
In that case the BSS138 solution would have the same issue ?
That's why I think on the long term it would be better to have dedicated 74F "push-pull" based adapters for each of the supported processors.
Understood.
Last edited by bprosman on Mon Sep 09, 2019 10:46 am, edited 1 time in total.

User avatar
hoglet
Posts: 8529
Joined: Sat Oct 13, 2012 6:21 pm
Location: Bristol
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by hoglet » Mon Sep 09, 2019 10:48 am

bprosman wrote:
Mon Sep 09, 2019 10:45 am
In that case the BSS138 solution would have the same issue ?
Yes, all bidirectional FET based level shifters will have this issue.

Dave

bprosman
Posts: 333
Joined: Sun Mar 29, 2015 10:27 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by bprosman » Mon Sep 09, 2019 10:55 am

One more question.

Instead of using a Schottky diode to transform the 5V from the "Host" system into 3V3 would a voltage regulator add any benefit ?

User avatar
hoglet
Posts: 8529
Joined: Sat Oct 13, 2012 6:21 pm
Location: Bristol
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by hoglet » Mon Sep 09, 2019 11:06 am

bprosman wrote:
Mon Sep 09, 2019 10:55 am
Instead of using a Schottky diode to transform the 5V from the "Host" system into 3V3 would a voltage regulator add any benefit ?
That's not what the Sckottky diode is doing.

The FPGA board already contains a 3.3V regulator (fed from several places, including directly from the VIN power pins on the 2x20 connectors).

The purpose of the schotty diode on the new adapter design is to prevent back-flow of current, in the event the FPGA board is powered from the USB port, and the host system is switched off.

Dave
Last edited by hoglet on Mon Sep 09, 2019 11:10 am, edited 2 times in total.

bprosman
Posts: 333
Joined: Sun Mar 29, 2015 10:27 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by bprosman » Mon Sep 09, 2019 11:29 am

The purpose of the schotty diode on the new adapter design is to prevent back-flow of current, in the event the FPGA board is powered from the USB port, and the host system is switched off.
Indeed, now I recall , was lost in "space" (aka my brain).

User avatar
myelin
Posts: 726
Joined: Tue Apr 26, 2016 9:17 pm
Location: Mountain View, CA, USA
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by myelin » Mon Sep 09, 2019 3:51 pm

hoglet wrote:
Mon Sep 09, 2019 10:42 am
You could omit the 1.5K pullup resistors, but then the level shifter would only drive to a maximum of about 3.2V. This might not be high enough for some CMOS devices.
Note that a lot of 80s/90s era CMOS devices still use TTL levels on their inputs, and all the Acorn machines I've looked at are like this at least for the address and data buses, so most of the time 74LVC buffers (74LVC125 for open collector, otherwise 74LVC245 or 74LVC16245) is perfect for communicating between them and non 5V tolerant logic.

(Lots of non-bus stuff need full CMOS levels though -- clocks on the 65C102, CL-PS7500FE, etc.)
Last edited by myelin on Mon Sep 09, 2019 3:52 pm, edited 1 time in total.
SW/EE from New Zealand, now in Mountain View, CA, making BBC/Electron hardware projects for fun.
Most interesting: Arcflash, FX2+PiTubeDirect Tube/Cartridge adapter, USB cart interface.

User avatar
flynnjs
Posts: 825
Joined: Tue Jul 06, 2010 9:33 pm
Contact:

Re: Cheap Xilinx LX9 Starter Board

Post by flynnjs » Mon Sep 09, 2019 9:24 pm

Dave and I had a longish conversation about using proper directional level shifters
and we decided for compatibilty that it would be the best thing. However, I wanted
to aim my adapter at any 40pin device, not just 6502 so it would not be possible to
have one direction pin from the FPGA for the entire data bus because you wouldn't
know which shifters that bus was on. It would therefore require TWO FPGA pins for
each IO (one for data one for direction) and there are not enough pins available on
the DE-0 nano headers (or the LX9 starter board which uses the same pinout).
So it was a cost/compatibility decision. The level shifter is cheap, as are the
starter boards. The shifter can be strapped for any pinout but the tradeoff is the
pull-ups which break a few systems.

The perfect solution would be something similar to the GODIL form factor (a
combined board) with a BGA FPGA and individually directional shifters. It wouldn't
be cheap. I have a draft PCB but I think the market would be more for the
professional market than hobbyists due to cost.

Post Reply