Covox sound upgrade

[peteym5]

I wonder if this is put on with a dual pokey (stereo pokey) board and address it at $D280-$D283. Which is in the same page as pokey. I am thinking about this because I believe an upcoming video upgrade might be using page $D5 or $D6, might be at $D5. Think that black box thing also uses the same memory area, Some people might look to put multiple upgrades in their computer. I am just looking to play it safe, see if no other upgrades are using $D6 and $D7. We should decide upon a standard memory location so people can develop software for it.

[Rybags]

Well, Neotracker already supports it, so it seems.

 

I don't see much sense in making things even more complex just to have it share POKEY's page.

 

The multiple upgrade headache has been around for years - that's the entire nature of 8-bit machines.

 

The other pain is that a lot of good stuff is coming out, but little is being done is the way of English documentation.

 

Page $D5 should be a no-go zone - practically all bank-switching carts use it.

[Rybags]

Sorry about the crap picture, but my digital camera decided to have a flat battery so I used the one on my phone.

 

 

I wasn't brave enough to risk soldering the thing into one of my machines just yet, so assembled a proto with just a 74HC573, using 4 bits from the joystick port output to control the thing (3 bits sound, 1 bit strobe for the latch clock). Used an RCA jack, and connected it to some PC speakers.

 

Worked OK, albeit a bit crackly.

 

I seriously might have to investigate SM resistors otherwise this thing will end up being enormous once put on a circuit board.

 

I'm considering actually building the thing as an external device, to plug into the cartridge port.

 

Then, the only mod I'll need to do internally is grab a feed from the D7XX CS line.

[peteym5]

Well, Neotracker already supports it, so it seems.

 

I don't see much sense in making things even more complex just to have it share POKEY's page.

 

The multiple upgrade headache has been around for years - that's the entire nature of 8-bit machines.

 

The other pain is that a lot of good stuff is coming out, but little is being done is the way of English documentation.

 

Page $D5 should be a no-go zone - practically all bank-switching carts use it.

 

The one upgrade I see a few people using is Videoboard XE, and I think they were talking about using page $D5, it might have changed since their last announcement. I actually thought the board was to be on the market by now but have not seen anything.

 

With these being wave playback channels, I always wondered how they work. I know you just don't store a number there and it plays back a tone. I also noticed there are no volume or control registers. Wonder if we can using for game sound effects.

 

I might be looking for an internal upgrade or a PBI/ECI upgrade and keep the cartridge port free.

[Rybags]

It works virtually the same way as POKEY's volume only mode. Except it's 8 bits per voice instead of 4.

 

So, you need to have samples or a wave table in memory.

 

Then, the program must store data in the registers at a regular interval.

 

Once per scanline gives about 16 KHz, every second about 8.

 

 

So, it's not so useful for games as it's too demanding on CPU resources. But, just fine for music.

[peteym5]

I was not aware there was a volume only mode. So the value of the byte is like the amplitude and faster you change it up and down, higher the pitch of sound it will produce. Change it less or more for volume. Am I getting this right. You certainly would have to be constantly updating these voices then. I would suppose doing it with a VBI is out also because that can only update 50/60 fps. Might be able to go alittle higher with a continuous ML loop. Wonder if something can be built with a separate processor and ram on a small board. Probably have to have the ram shared and bank switched so stuff can be transferred from the main computer.

[Rybags]

I suggested a coprocessor board in another thread - but I wasn't thinking sound, more like having it do more important stuff like software sprites.

 

To get anything resembling quality sound with volume-only, you need to change values at least 4,000 times a second - preferably two or four times that amount.

 

Of course, it's main use is to do triangle, sawtooth waves, and stuff like speech. And drumbeats.

 

Back to Covox - I'm considering using discreet resistor values rather than a resistor ladder. But then, I guess it then brings up the problem of tolerance induced errors.

 

You can buy resistor ladders machine made in DIP style - problem is the shop I go to doesn't have them.

 

And the only surface mount ones they have come in a packet of about 50x70 values for about $50.

[peteym5]

I think a people on here may look for upgrades that can enhance the Atari 8-bit functions for retro game play. I am not sure hardware upgrades that dedicates most of computers resources to playing back sampled sounds are not practical. Also have to consider, the PC would be a better playback device for sampled sounds. Maybe if this upgrade was accompanied with a 65816 cpu at higher speeds or its own cpu on a board probably be what I would be look for in an upgrade. To have better sound effects in a game.

 

This does have me wondering, how hard would it be to program the Pokey chip to do a similar function on wave playback. I know there is the other thread on here that involves wave playback.

[MEtalGuy66]

Ok. Heres one posible layout..

 

This would piggyback in the antic socket in a 130xe and only require 1 wire (in addition to the audio outputs) to hook up.

 

Wouldnt fit in an 800XL though.. Or it would, but it'd have to be a 15 wire hookup.. (plus the two audio outputs).. because there no room above the antic socket in an 800XL...

 

Another note Ill make, which I just thoght of is that this board would overhang the GTIA and part of the OS ROM, and thus wouldnt fit in the same machine with a videoboard XE or any of the ATARIMAX upgrades that go in the ROM socket....

 

Unless you opted for the 15-wire hookup and stuck the board elsewhwhere...

 

I could rearange the board layout to put all the stuff to upper right of the antic chip, thus overhanging the CPU and part of the PIA...

 

 

Parts list:

 

4 x 74LS574

 

1 x 74LS138

 

4 x 2.4k "straight through" DIP resistor array

 

8 x 2.4k SIP resistor packs

 

8 x 1/4w 2.4k resistors

 

9 x 100nf ceramic caps

 

1 x 3-PIN .100"-spacing header

 

2 x 20-PIN .100"-spacing header

 

Optional:

 

Sockets for all the ICs

Rubber feet to support the free-end of the board.

Edited December 17, 2007 by MEtalGuy66

[peteym5]

Been reading and replying to people on another thread who might be looking to rebuild or upgrade an Atari computer. It has been mentioned about using a Arm processor to enhance the graphics functions of the computer. I wonder if this processor be more practical to handle the wave sound playback with this chip?

Edited December 29, 2007 by peteym5