FPGAARCADE minimig compatible board, comments?

[tonyyeb]

mikej wrote:

Edit: clicking on the link doesn't seem to work, but then hitting reload does. Odd.

You have a full stop at the end of the link.

[mikej]

"Excellent work/news Mike.

I hope you don't mind if we create a new section over on www.Minimig.net for your board."

Sure Darrin, feel free.
The forum at fpgaarcade will be active shortly as well.
/Mike

[mikej]

Latest schematics are up if anybody wishes to have a look / comment. A few days to go until manufacture now....

www.fpgaarcade.com

Cheers,
MikeJ

[jkonstan]

Mike,

After looking at your updated schematic, the updated design looks pretty good to me. The only thing that I might have done differently is the power supply design because using a fixed 5V input power supply can lead to a fried pcb if someone uses the wrong power adapter (wall wart). At a Xilinx training seminar that I attended last year, our instructor fried a brand new Spartan3A DSP evaluation board by using the wrong power adapter (used a 12V power adapter instead of the required +5V power adapter).

Thus, you should populate zener D9 and R121 polyfuse and depopulate R120 for protection against this occurance since these populated pcbs are likely to cost a fair amount.
Since Dc to DC switchers were used, your other option would have been to just design the switchers with a wider DC input voltage range (5v to 19v) and add a +5V output switcher to the design.
 

Keep up the good work and keep us posted on the prototype pcb fabrication!

 :-)

[Illuwatar]

Did a quick look at the schematics - interesting thing. I may be interested in one if the price is acceptable. But as the previous poster said - requiring external +5V with no tolerance is a bummer. That was the first thing I modified in the MiniMig design when I made the mini-itx version. Polarity reversal protection, wide input voltage acceptance (an on-board switching regulator for the +5V - Something out of the SimpleSwitcher series maybe) and over voltage protection in combination with EMI-filters.

[mikej]

Hi Chaps,
Thanks for the comments.

One thing I added in the latest version was the polyfuse and TVS diode for this reason. They will be populated assuming there is no problem with them.

The TVS diode will start to clamp at 5.somthing volts and the polyfuse will open. Likewise for reverse polarity the diode will go into full conduction and the fuse will open (fast). It is not a perfect solution as the 5v devices are still exposed to some risk, but I think it is an acceptable compromise. There is not much on the 5V rail apart from the switchers and protection diodes.

I would prefer a 12v to 5v step down like you did, but I can only fit it on if I compromise the other power supplies, and I am expecting to be pulling quite a bit of power on the FPGA core and 3V3 rails. The 2V5 supply also drives the termination regulator so I can't do much there either. I am trying to keep the cost down as much as possible also.

I imagine that normally the board will be used in a mini-itx case with a decent 5v regulated supply.


These polyfuses by the way fix themselves when the problem is removed.

Best,
Mike.
oh Illuwater, I am also in Sweden (Stockholm) although I am not Swedish.

[mikej]

There is going to be another update.

Originally for hard disk usage I was going to use an IDE connector and either hard disk or CF disk on the daughter card. It would be a great feature to have hardfile support from the SD card for the base platform. The AVR SPI transfer speed in this case is limited to about 300KBytes per second. This is ok for floppy and booting, but not great.

So, I am going to add a multiplexer which lets the FPGA master the SD card directly. The AVR will still contain the knowledge of the file system and talk over the current SPI link to the FPGA. The FPGA will then enable it's second SPI interface (reusing the 4 IO programming pins which conveniently already go to the AVR part of the PCB) and take over the job. Depending on the SD card we should get transfer speeds of several MBytes per second. This will delay the board a week or so.
so comments can still change things
/Mike

[mikej]

While I am changing the SPI routing, Jakub has convinced me to replace the AVR with the ARM7S chip he uses for the hardfile demo. Amazingly, the cost of the chip and the USB socket is the same as the AVR. I have managed to fit all on the PCB, just need to fix the routing (again).

The main benefit is I can pick up Jakub's work for hardfile support, which save time. It also goes faster, and we have gained a USB port for flashing the microcontroller - and we can potentially use the USB port from the FPGA.

Updated schematics and layout in a few days. Assembly pushed back two weeks.

/Mike

[tonyyeb]

@mikej

Remind me Mike, how much are these boards going to be (assembled)? And will we be ordering from you or a supplier?

[mikej]

At the moment there are too many variables to get an exact pricing, I am waiting for some more quotes. The aim is less than 200E for boards from the initial small run. Production boards should be significantly cheaper. There are a few options for suppliers, but initially they can be ordered through me.

Best,
Mike.

[Palm]

Hi. You know, Toni Westbrook made some PSX64 adapters which lets you use PSX controllers amiga/atari/c64. The nice thing is that you can use wireless psx controllers, plus the pic (?) on his adapter opens for macro-editing buttoncombinations for the psx buttons not used as fierbutton. This is programmable directly from the psx controller using dedicated buttons for this.

It would be nice if you were able to implement this on your pcb so that we can natively use psx ontrollers via this mega8 chip. Of course, general outputs for vintage joysticks are also needed

This enables "sofa friendly playing (SFP)" when they are wireless :-)

http://www.synthdreams.com/psx64.php for more info and you can find schematics + firmware here: http://www.synthdreams.com/knowledgebase?art=10


Regs
Espen

[mikej]

Latest ARM schematics and layout update.
www.FPGAArcade.com

right, this is it, no more changes....

[mikej]

For those interested I have posted pictures of the Replay board PCB I have just brought back from China.

www.fpgaarcade.com

I will get the boards built this week, but it will take a little while before we have the system up and running.

/Mike

[mikej]

Board is complete and initial testing is going well.
Power supplies, FPGA and ARM controller all working ok.
/Mike

[jkonstan]

Keep us posted on your progress on the FPGAARCADE board Mike.

 :-)

[Darrin]

mikej wrote:
Board is complete and initial testing is going well.
Power supplies, FPGA and ARM controller all working ok.
/Mike

Great news.  What sort of transfer speeds are you getting from the hard file, better than on the Minimig v1.1 or the same?