Easter holiday project - Dual pokeys on an Ultimate Cart

[electrotrains]

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...

 

 

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.

SynthyGambol_vhdl_pokey.mp3

Edited April 1, 2016 by electrotrains

[TheMontezuma]

What about SIDs?

[+MrFish]

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

[Level42]

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

[gozar]

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

[electrotrains]

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!

[gozar]

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?)

 

 

Sent from my iPhone using Tapatalk

[Kyle22]

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?

[foft]

Cool!

 

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

[electrotrains]

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 April 1, 2016 by electrotrains

[bugs]

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

 

....award winning feature creep lol

 

 

 

Sent from my SM-G920W8 using Tapatalk

[Defender II]

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.

[pazuzu72]

On 4/1/2016 at 5:58 PM, electrotrains said:

 

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!

Hi, but is the firmware for this project working? I could redo the pcb with the addition of the low pass filter and the headphone jack if that's ok with you. It would be really cool!!!!!!!!