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Quadro Pokey PCB (4x for TMC2)

Pokey Chipmusic TMC Quadro 4x

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#51 jmccorm OFFLINE  

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Posted Mon Mar 19, 2018 12:34 PM

NOTE: If I'm understanding this correctly (and I could very well be wrong -- I'm out of my depth here), it might suggest a cool additional feature, not actually part of the Major Havoc quad pokey but could be built onto a quad POKEY for 8-bit machines: a register which allows the audio channel from the 4th POKEY to replace/modify ground on the other channels?

 

This seems to be even more complicated. So, if someone with some audio electronics skills wants to chime in, here is a ZIP with the Major Havoc schematics (individual pages are in TIFF format). I've pre-digested this document, so to save you the time, here are the good parts:

 

Page 10A contains the Quad POKEY and the surrounding circuit. Find the large IC "QUAD CUSTOM IO" with the four audio outputs in the lower right of the chip. OUT1-3 are tied together and fed into a circuit, and OUT4 gets its own unique circuit. Then it appears that the output of those two circuits are tied together, and then all of it is processed yet again in a way that creates an AUD1 and AUD2 output that goes to the Atari Audio Regulator II board (as an audio amplifier). This is what mytekcontrols and shupac were talking about.

 

Page 02A picks up the AUD signals on the Atari Audio Regulator-II board, which is a standardized PCB (but with multiple revs which certain games will require). It creates speaker level outputs. Notice that the SPKRx-RETURN lines are tied to ground, which later a speaker would normally be connected to the SPKRx and SPKRx-RETURN lines.

 

Page 01B is where we take the SPKR* outputs from the AR-II board and actually feed them into the speakers. The oddity, as described earlier, is that normally, the SPKRx-RETURN lines from the AR-II board are used as audio ground and SPKRx have the audio signal. Instead, here, SPKR1 and SPKR2 are fed to the speakers (with no SPKRx-RETURN lines being used). So that's weird. And as mentioned, the speakers are also oddly wired. One speaker is connected directly to SPKR1 and SPKR2. Then there are two speakers which are connected in series before they are connected to SPKR1 and SPKR2. So this was the oddity on the other side of things that I was talking about.

 

All of this is so incredibly convoluted. Perhaps someone could help us make sense of what is going on here? Perhaps it was a way to select between sets of speakers? [Specifically, a way to dynamically balance the output of 3 POKEYs between two channels rather than having two fixed audio channels with 2 unique POKEYs on each side?] Or is it as I originally imagined, a way to put a cool twist on the standard POKEY output without burning CPU? Both? Something entirely different? This one is odd, so some expertise would be appreciated.

 

Possibly worth further examination: how the audio was handled in the official Major Havoc to Tempest conversion PCB kit. The kit made no modification to the cabinet, so it used the more conventional speakers of the Tempest cabinet. (This is how I played Major Havoc. The kit had an authentic Major Havoc PCB, but it included a wiring harness that adapted it to the wiring of a Tempest game's cabinet. It effectively replaced the Tempest arcade PCB.)


Edited by jmccorm, Mon Mar 19, 2018 1:05 PM.


#52 Matej OFFLINE  

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Posted Mon Mar 19, 2018 1:09 PM

Hey guys! Dont develop it. We have it almost done (95%).
Screenshot_20180319-185434.png

#53 mytek ONLINE  

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Posted Mon Mar 19, 2018 5:03 PM

Hey guys! Dont develop it. We have it almost done (95%).
Screenshot_20180319-185434.png

 

Matej I'm seeing individual Pokey chips in your layout. Where are people suppose to get 4 Pokeys in this day and age?

 

Best Electronics will only sell 1 maybe 2 (if you beg) per purchase, and his stock is dwindling fast. I really think it's time to do this via FPGA, and save what Pokeys are left for stock A8's and stereo boards. And it looks like the FPGA solution for quad Pokeys is getting ever closer to reality, just need to integrate the standard SIO, keyboard, and paddle functions to make it complete.



#54 Matej OFFLINE  

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Posted Mon Mar 19, 2018 5:10 PM

OK so we will make quadpokey for musicians (they love real chips) and you for gamers/users/arcade fans.Thats OK...
I have 20x pokey at home.But yes I am fanatic...FPGA is very good.There are also companies which can make from fpga normal asic chips.So can be interesting for future!!!

#55 mytek ONLINE  

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Posted Mon Mar 19, 2018 5:13 PM

OK so we will make quadpokey for musicians (they love real chips) and you for gamers/users/arcade fans.Thats OK...
I have 20x pokey at home.But yes I am fanatic...FPGA is very good.There are also companies which can make from fpga normal asic chips.So can be interesting for future!!!

 

i love real chips as well  :thumbsup:  :) . But sometimes due to limited availability you need to substitute newer technology. Do you have a picture of one of your new boards?



#56 Matej OFFLINE  

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Posted Mon Mar 19, 2018 5:34 PM

Not finished.Developer is playing with smaller footprint and better mixing (gtia+pokeys).But will post first prototype here!

#57 Matej OFFLINE  

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Posted Tue Mar 20, 2018 2:48 AM

Guys can you than test TMC2 music composer by Jaskier??? There is 4x pokey support. Just few notes each channel... Also maybe release your core under some kind of friendly licence??? Maybe someone will add filters like on C64 are. In future... Thats cool on FPGA that can be upgradable.Maybe downloadable core on Ataribits.Or just well documented...For future.

#58 electrotrains OFFLINE  

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Posted Tue Mar 20, 2018 5:14 AM

I'm happy to contribute my sources for dual pokey on the MAX10 fpga if this helps get an FPGA version going. The code is largely foft's VHDL pokey implementation, with just a bit of glue code from me to get it working on an Atari cartridge.

 

I may have posted it earlier in the thread (Yes - I did!), but here is my original post about the project, along with some sample sound output from TMC.

https://atariage.com...-ultimate-cart/

 

I didn't release the source originally, since it was just a quick hack/experiment, but if there is real desire for a dual/quad pokey implementation on an FPGA, then there's not actually much work to do... Add a few components to the PCB design for audio output, tweak the VHDL, and that's pretty much it. Happy to lend a hand if anyone is up for it...

 

Robin



#59 mytek ONLINE  

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Posted Tue Mar 20, 2018 11:06 PM

Instead of trying to replace the extended functionality of the stock Pokey in our A8's, why not retain it for what it's good for and do something more like this.

 

FPGA 4-CH Pokey A8 Board.png

 

I reserved a pin on the header for perhaps a MONO mode select (would require some analog switches), or perhaps for an additional address line if you wanted to add even more cores.

 

Stock audio still exists on the monitor port.



#60 Matej OFFLINE  

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Posted Wed Mar 21, 2018 4:23 AM

I like it. How you will do stereo on monitor plug??? Extra pin??? Or have stereojack also in case and some kind of switch between monitor and jack or signal will be outputed to both at same time???

#61 Matej OFFLINE  

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Posted Wed Mar 21, 2018 4:37 AM

Also in far far future maybe few build in dsp effects will be nice.Like reverb,flanger,echo...Controlable via cpu.I mean effect for one core or choosen channel...

#62 Matej OFFLINE  

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Posted Wed Mar 21, 2018 4:37 AM

https://m.youtube.co...h?v=ANxHyCAYGp0

#63 mytek ONLINE  

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Posted Wed Mar 21, 2018 7:43 AM

I like it. How you will do stereo on monitor plug??? Extra pin??? Or have stereojack also in case and some kind of switch between monitor and jack or signal will be outputed to both at same time???


In essence this is no different than the Simple Stereo board, and both left and right audio is brought out to a header for the user to terminate how ever they see fit (i.e., RCA jacks, or unused pin on monitor jack used for right channel). Since the A8's stock Pokey audio output goes through a buffer before connecting to the monitor jack, having that same audio output direct from the stock Pokey chip connected to the mixing circuit on this proposed 4-CH piggyback board allows simultaneous outputs with no switch required. However although it isn't shown, it might be nice to provide electronic switching to allow the stock Pokey's single output to pass through both left and right channels for mono operation (programs that don't support stereo), same as done on 1088XEL or Simple Stereo with U-Switch board added.

Speaking of the 1088XEL, a slightly different version of this board could be made to drop into and utilize the onboard mixer of the 1088XEL, thus automatically routing both channels to the 3.5 mm and the DIN-13 jacks.

So as it stands right now, the present proposal gives you 8 voices per audio channel output. Of course by adding an additional address line and cores this could be doubled. But at some point you would hit diminishing returns when considering CPU time available for both sound and graphics where games are concerned. A!though in a purely sound oriented application with simple graphics, the additional cores might be nice and put to use creating some great music.



#64 Vyper68 OFFLINE  

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Posted Thu May 10, 2018 12:42 PM

As a fan of 8-Bit Chip Music in general and the POKEY in particular 'cos I'm an Atari user, I can see the appeal of just having the Audio section of the POKEY "emulated" having no electronics training i just wondered how realistic is this concept to come to fruition? and when could we maybe expect something to happen as regards production of these type of boards?

They ( POKEY's ) seem to be quite scarce at the moment in Europe and something like this would be great - maybe you could even toggle between Dual or Quad POKEY's via a switch of some type.







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