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Easter holiday project - Dual pokeys on an Ultimate Cart

pokey cartridge fpga ultimate cart

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#1 electrotrains OFFLINE  

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Posted Fri Apr 1, 2016 6:15 AM

Thanks to the efforts of foft (Mark Watson) and his Atari FPGA project, there is an open source FPGA pokey implementation available. As a little Easter bank holiday project, I thought I'd have a go at using it to make a dual pokey cartridge using a prototype of the Ultimate Cart as the starting point...

 

pokey.jpg

 

Two of the fpga pins act as audio left and right, and I've hooked them up to a low pass filter on some perfboard, along with a 3.5mm stereo jack (which leads to my TV's audio input).

 

It was pretty easy to make a firmware for the Ultimate Cart that included two of foft's pokeys, his DAC and a bit of VHDL to hook them up to the cartridge port.

 

Then I modified TMC and RMTPlayer (with a hex editor) to output to the two pokeys at $D50x and $D58x.

I guess technically this atari has 3 pokeys now (one inside, and two on the cartridge). The two pokeys use about 10% of the Ultimate Cart's FPGA, so there is plenty room for more.

 

This was just for fun, and perhaps to show a little of what is possible with a FPGA hooked up to the cart port. To make a proper external dual pokey, we'd probably want to use ECI+Cart port, so the pokeys could appear in the correct places in the memory map.

 

MP3 of TMC playing via the dual pokeys attached.

Attached Files


Edited by electrotrains, Fri Apr 1, 2016 6:28 AM.


#2 TheMontezuma OFFLINE  

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Posted Fri Apr 1, 2016 6:57 AM

What about SIDs?



#3 MrFish OFFLINE  

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Posted Fri Apr 1, 2016 7:16 AM

Nice choice of tunes btw. Haven't heard that one from X-Ray in a while.



#4 Level42 OFFLINE  

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Posted Fri Apr 1, 2016 9:34 AM

Very cool, I can never get enough of POKEY, especially stereo :)



#5 gozar OFFLINE  

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Posted Fri Apr 1, 2016 9:38 AM

I'm assuming this can't be added to the current Ultimate cart? :-)



#6 electrotrains OFFLINE  

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Posted Fri Apr 1, 2016 9:58 AM

I'm assuming this can't be added to the current Ultimate cart? :-)

 

The need for the low pass filter (2 resistors + 2 caps) and headphone jack would make it a pretty messy addition to the board as it stands, which is why I haven't posted the firmware or source for this. Also, although there are spare pins on the FPGA, they are not brought out to a header.

 

Of course someone could always redesign the PCB a bit, and add an audio jack to the board. Then there could be an option on the boot menu to enable dual pokey mode... or SID mode... or....

 

But I think that it would be better still to make a PBI/ECI+Cart version of the ultimate cart, then the pokeys could live at their normal location. Plus it could act as a RAM expansion too.

 

SD Multicart + 1 Meg RAM + Dual pokey all one one board - that would be a nice thing!



#7 gozar OFFLINE  

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Posted Fri Apr 1, 2016 10:05 AM

Well, if you're going to add all that, then add alternate OS mode, stackable carts, and SD card access as a hard drive. :-)

That would be an amazing device. Oh, and an RTC.

(Cart mode wouldn't work on the PBI, right?)


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#8 Kyle22 OFFLINE  

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Posted Fri Apr 1, 2016 10:37 AM

I propose a dual purpose board in 800 card form factor. +5 and ground picked up from the card slot, with an additional power connector for XL/XE users.

This would simply plug in the 800 with a short PBI cable to the Incognito, or in XL/XE format, the board could be in a case with a PBI cable to the computer.

 

One board for both 800 Incognito and XL/XE.

 

Would there be enough room in the FPGA for a VBXE along with sound chip cores?



#9 foft ONLINE  

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Posted Fri Apr 1, 2016 2:03 PM

Cool!

The pbi/eci+cart could be the Atari's Chameleon... Perhaps include a hdmi and vga port too:)

#10 electrotrains OFFLINE  

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Posted Fri Apr 1, 2016 2:06 PM

Cool!

The pbi/eci+cart could be the Atari's Chameleon... Perhaps include a hdmi and vga port too:)

 

Hey I don't think I actually committed to building such a thing!

 

EDIT - though I am tempted.


Edited by electrotrains, Fri Apr 1, 2016 2:07 PM.


#11 bugs OFFLINE  

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Posted Fri Apr 1, 2016 9:08 PM

Wow...from a dual pokey to a new Atari in under 24hrs.

....award winning feature creep lol



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#12 Defender II OFFLINE  

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Posted Fri Apr 1, 2016 9:21 PM

Cool!

The pbi/eci+cart could be the Atari's Chameleon... Perhaps include a hdmi and vga port too:)

 

 

Hey I don't think I actually committed to building such a thing!

 

EDIT - though I am tempted.

 

OK, put me down for one for now, maybe two. ;)







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