FPGA Pokey replacement - discuss!

[VectorGlow]

$40 per replacement Pokey isn't too bad - if it's a choice between that and having a board that isn't fully functional I feel that most people would go for it.

How about quad Pokey support?

 

[Nes4life]

I've got a few requirements for a flexible 40 pin replacement module.

1 - 5V CPLD such as ATF1508AS

2 - PSOC4 from Cypress

3 - Spartan7 FPGA + logic translators

...probably looking at 40$+ per module still

Hey Mike, can you give us a bit of information on these options? Sounds really good and quite interesting!

Is there an entry-level / bare-bones version that'd work or do you essentially need all of these 'requirements' to get any type of Pokey replacement?

Don't be discouraged if $40 (£30) is as low as you can go at the moment; that's basically the current tipping point anyway as NOS stock becomes unavailable. It's also worth considering that these modern replacements perhaps will last longer than their 30 year old counterparts. Do these modern components (FPGA / CPLD) become cheaper over time or do they just become unavailable and a new faster / larger version takes its place at the same price?

 

[John Bennett]

If a working model is created, then perhaps we can create a bespoke module at a later date if there's significant cost savings over a universal version? (Max V CLPDs are available under a tenner).

 

[foft]

Mike J pointed out this thread to me. Did you see my project?
http://atariage.com/forums/topic/282166-abbuc-hardware-contest-entry-pokeymax/?fromsearch=1

 

[Mitchell Gant]

Mike J pointed out this thread to me. Did you see my project?
http://atariage.com/forums/topic/282166-abbuc-hardware-contest-entry-pokeymax/?fromsearch=1

Welcome to the forum. You've shot straight into the lead for POKEY replacement here!

Fixed your link:

http://atariage.com/forums/topic/282166-abbuc-hardware-contest-entry-pokeymax/?fromsearch=1

That's an impressive bit of PCB layout there for it's required size, as well as more functionality than any of the arcade games (that I'm aware of) will need to use.

I like the chip enable logic to combine voltage level shift and the two inputs.

The only two drawbacks I see are the cost and the size of the PCB overhang for fitting into some arcade PCBs.

What are the exact dimensions of your PCB?

I just measured a Star Wars sound board spacing and from pin 1 of the first POKEY to pin 1 of the second I measure 24mm.

On a Space Duel/Gravitar I measure 26mm, and a Tempest it's about 35mm.

So the Star Wars is the closest chip spacing I measured in the PCBs I have to hand.

If your PCB is wider than that then there's a couple of options. One is to redesign the PCB so it loses the JTAG header and squeeze it to be narrower.

A better option that also improves the other drawback of cost is to make it a dual POKEY and make one of your POKEYMAx's replace two chips on the game board. You'd need to link over the /CS and audio out pin from the second POKEY, and adjust your VHDL to suit.

It would only work for Star Wars though, as the other games with two POKEYs use the pot inputs on each chip.

A "Quad POKEY" is simply 4x POKEY dies on a single carrier, with only the 4x /CS pins brought out (no CS), and a single bank of pot inputs, I *assume* from the first POKEY. I guess you would need a PCB re-design to cater for that though.

I think looking at a standard single/dual POKEY would cater for many arcade repairs right now, and worry about Quad POKEYs later.

A recent bulk order here on UKVAC got almost 30 chips ordered, so building 100 or so POKEMAx's could easily achieve sales and keep costs lower. I've replaced probably 10 faulty chips or so myself over the about last 2 years. There is certainly a demand for them!

If you have any built and for sale I'd be willing to buy a couple and test them out in a few game PCBs that I have. I have a couple of USB Blasters and some Quartus experience, so could do updates to try out those options if you liked. Or if you just have bare PCBs I'm capable of building SMT parts myself no problem. Though that looks like a BGA MAX10 you're using, so would surely need a solder paste screen and reflowing in an oven?

 

[VectorGlow]

I was also thinking of the overhang issue on some boards, I like your ideas. I love what foft has done so far.

VectorGlow2018-10-18 08:45:05

 

[Nes4life]

This is exactly what we need! @foft it'd be great if you'd let one or two of the guys here help out in reducing the size of the design so we can get it down to nearly the same footprint as the original, or we'd love to work with you on getting it tested on a selection of arcade machines and make improves / adjustments as needed. Otherwise, are you open-sourcing the design or happy to share it with us? Looks like you've put a lot of work in to this!

 

[foft]

What are the exact dimensions of your PCB?

52mmx29mm

I just measured a Star Wars sound board spacing and from pin 1 of the first POKEY to pin 1 of the second I measure 24mm.

On a Space Duel/Gravitar I measure 26mm, and a Tempest it's about 35mm.

So, it needs to be a little smaller for Star Wars and Space Duel.

There is an easy 1mm by removing the extra audio output pins, which would be 52mmx28mm

Then the power circuit and jtag would need relocating.

There is more space on the bottom half because I don't need the paddle capactors and resistors, I had included those in error. I think that will be enough room for the power circuit. The jtag could be replaced with a smaller header (and use an adaptor).

A better option that also improves the other drawback of cost is to make it a dual POKEY and make one of your POKEYMAx's replace two chips on the game board. You'd need to link over the /CS and audio out pin from the second POKEY, and adjust your VHDL to suit.

Well it is currently a dual pokey... Though /CS from pokey2 would need level conversion I guess.

I'd be keen to modify the PCB so that it can work as a single, dual and quad pokey. I wonder how different the pinouts are.

A "Quad POKEY" is simply 4x POKEY dies on a single carrier, with only the 4x /CS pins brought out (no CS), and a single bank of pot inputs, I *assume* from the first POKEY. I guess you would need a PCB re-design to cater for that though.

I think there is not room on the exisitng FPGA for quad pokey. That said, with some refactoring and sharing of logic it will not be a problem.

A recent bulk order here on UKVAC got almost 30 chips ordered, so building 100 or so POKEMAx's could easily achieve sales and keep costs lower. I've replaced probably 10 faulty chips or so myself over the about last 2 years. There is certainly a demand for them!

A larger quantity order will indeed make it cheaper. I also need to change the pcb layout to increase the spacing under the FPGA. The PCB company charged me a lot more because I have 5 mil spacing under there.

If you have any built and for sale I'd be willing to buy a couple and test them out in a few game PCBs that I have. I have a couple of USB Blasters and some Quartus experience, so could do updates to try out those options if you liked. Or if you just have bare PCBs I'm capable of building SMT parts myself no problem. Though that looks like a BGA MAX10 you're using, so would surely need a solder paste screen and reflowing in an oven?

Yes I have a few floating around here. Some paddle circuits may not work since as I mentioned I accidentally included the resistor/capactors that are also on most motherboards...

Yes it is a .8mm BGA part, so would need an oven. Since some of the other parts are so small I got them professionally assembled.

 

[foft]

This is exactly what we need! @foft it'd be great if you'd let one or two of the guys here help out in reducing the size of the design so we can get it down to nearly the same footprint as the original, or we'd love to work with you on getting it tested on a selection of arcade machines and make improves / adjustments as needed. Otherwise, are you open-sourcing the design or happy to share it with us? Looks like you've put a lot of work in to this!

Yes it'd be good to test it out 'as is' on some arcade machines. Then we can come up with a revision 2 to fix anything found, try to reduce cost further and also to make it smaller to fit everywhere.

 

[Nes4life]

Just an update that this project is very much still underway. @foft has sold Neil & I a PokeyMax or 2 and is working on getting the software suitable for a few of the games. I'll keep you all posted as to when either of us have it in a pcb. We will be working toward improving the design for arcade and (if possible) making it more affordable.

 

[VectorGlow]

Excellent, thanks for the update and thanks to those working to make this happen.