Atari Analog Input - A/D Converter

[Blues76]

Hello,

 

Given the topic about plugging a guitar into the A8, I decided to open a new thread to discuss about what people know about getting Analog Input (e.g Guitar, Voice...) into the Atari. To Begin, I was given a few links from which, the most important (to me) is here:

http://www.atarimania.com/faq-atari-400-800-xl-xe-what-sound-digitizers-samplers-were-produced-for-the-atari_52.html and

 

which contains the list of some known devices / projects and a review of one here: http://www.atarimagazines.com/v5n9/AtariVoices.html

 

... now, given that we are in 2011 it's difficult one to find one, but just in case, if anyone has one to sell at a reasonable price, PM me.

 

 

Now, how difficult would it be to make an upgrade to make this possible. I don't know much about electronics, so for me this things are always difficult.

 

thanks for help and I'm looking forward to hear your comments, ideas and anything else about the topic...

[russg]

Hello,

 

Given the topic about plugging a guitar into the A8, I decided to open a new thread to discuss about what people know about getting Analog Input (e.g Guitar, Voice...) into the Atari. To Begin, I was given a few links from which, the most important (to me) is here:

http://www.atarimania.com/faq-atari-400-800-xl-xe-what-sound-digitizers-samplers-were-produced-for-the-atari_52.html and

 

which contains the list of some known devices / projects and a review of one here: http://www.atarimagazines.com/v5n9/AtariVoices.html

 

... now, given that we are in 2011 it's difficult one to find one, but just in case, if anyone has one to sell at a reasonable price, PM me.

 

 

Now, how difficult would it be to make an upgrade to make this possible. I don't know much about electronics, so for me this things are always difficult.

 

thanks for help and I'm looking forward to hear your comments, ideas and anything else about the topic...

 

I had a 'Parrot' device at one time, don't know where it is now. It took input from a device connected to the joystick port.

You could digitize any sound.

I may have sold it, anyway I don't know where it is.

[Blues76]

Hello,

 

Given the topic about plugging a guitar into the A8, I decided to open a new thread to discuss about what people know about getting Analog Input (e.g Guitar, Voice...) into the Atari. To Begin, I was given a few links from which, the most important (to me) is here:

http://www.atarimania.com/faq-atari-400-800-xl-xe-what-sound-digitizers-samplers-were-produced-for-the-atari_52.html and

 

which contains the list of some known devices / projects and a review of one here: http://www.atarimagazines.com/v5n9/AtariVoices.html

 

... now, given that we are in 2011 it's difficult one to find one, but just in case, if anyone has one to sell at a reasonable price, PM me.

 

 

Now, how difficult would it be to make an upgrade to make this possible. I don't know much about electronics, so for me this things are always difficult.

 

thanks for help and I'm looking forward to hear your comments, ideas and anything else about the topic...

 

I had a 'Parrot' device at one time, don't know where it is now. It took input from a device connected to the joystick port.

You could digitize any sound.

I may have sold it, anyway I don't know where it is.

 

I'll keep checking ebay... it would be a nice add-on to the atari to have

[Fox-1 / mnx]

Now, how difficult would it be to make an upgrade to make this possible. I don't know much about electronics, so for me this things are always difficult.

 

You first have to decide which way you want to go. Basically there are 2 ways:

 

1. Samples must be playable on standard Atari without the need of extra hardware.

 

In this case you just need a simple 4-bit A/D converter which you can connect to the cartridge port or a joystick port. It depends on the sampling software you want to use which way to go. Since PoKey can output 4-bits samples anyone can replay them on standard Atari. No separate D/A converter required.

 

 

2. Samples are playable on Atari but requires additional hardware (D/A converter)

 

In this case you need 2 devices. 1 For making samples (A/D) and 1 to replay them (D/A). 8-bits should be enough. More is possible but is of no use. The big disadvantage is that someone who hasn't got the 8-bit D/A converter can't replay the samples (at 8-bit resolution). To replay 8 bit samples on PoKey you need to convert them first (on the fly or at forehand) to a 4-bit or 6-bit resolution.

 

 

I guess Alphasys will jump in here. She wrote several articles about sampling in Atari magazines.

[Rybags]

There's a simple circuit design around somewhere that lets you just use a POT input on the joystick port for A->D conversion.

 

You can use fast potscan mode, so it'll be good for just under 8,000 samples/second.

 

Personally I just use the PC for that kind of stuff - any decent modern machine will do 16 or 24 bit sampling at 192 Khz, so you can start with top quality data then just reduce it to the bitsize and rate you want later.

[Blues76]

Now, how difficult would it be to make an upgrade to make this possible. I don't know much about electronics, so for me this things are always difficult.

 

You first have to decide which way you want to go. Basically there are 2 ways:

 

1. Samples must be playable on standard Atari without the need of extra hardware.

 

In this case you just need a simple 4-bit A/D converter which you can connect to the cartridge port or a joystick port. It depends on the sampling software you want to use which way to go. Since PoKey can output 4-bits samples anyone can replay them on standard Atari. No separate D/A converter required.

 

 

2. Samples are playable on Atari but requires additional hardware (D/A converter)

 

In this case you need 2 devices. 1 For making samples (A/D) and 1 to replay them (D/A). 8-bits should be enough. More is possible but is of no use. The big disadvantage is that someone who hasn't got the 8-bit D/A converter can't replay the samples (at 8-bit resolution). To replay 8 bit samples on PoKey you need to convert them first (on the fly or at forehand) to a 4-bit or 6-bit resolution.

 

 

I guess Alphasys will jump in here. She wrote several articles about sampling in Atari magazines.

 

I think option 1 is enough...

Is true that a any fast computer now day can do so much more, but the idea is just to play with the atari and see what I can get...

I would like to see if I could get the guitar tuner I did into the atari but 8,000 samples per second it may not be enough.

 

Now, I'm still left without an idea of how to build (or where to get) this add-on to be connected to the joystick port

 

 

For option number 2, how about using the stereo add-on (stereo expansion rev 2.1) http://translate.google.de/translate?u=http://mega-hz.no-ip.com/Angebote/Stereo/Stereo_small.html&sl=de&tl=en&hl=&ie=UTF-8

 

to the D/A to be able to get a better resolution...

[+David_P]

There's an ANTIC article on building your own mono input, using the POT, and including software. A quick scan of the archive didn't turn it up, but I'm certain someone out there can recall it...

 

Edit to add: And here it is:

 

http://www.atarimagazines.com/v8n8/anticsamplingproc.html

 

The Antic Sampling Processor

Edited February 21, 2011 by David_P

[UNIXcoffee928]

There's an ANTIC article on building your own mono input, using the POT, and including software. A quick scan of the archive didn't turn it up, but I'm certain someone out there can recall it...

Whoo-hoo, here it is!

http://www.atarimagazines.com/v8n8/anticsamplingproc.html

 

 

Edited February 21, 2011 by UNIXcoffee928

[UNIXcoffee928]

...& it references this older article:

 

http://www.atarimagazines.com/v2n4/talkischeap.html

 

 

[Blues76]

Great

[+Allan]

Check out the book "Your Atari Comes Alive"

 

It's the last book in the this page.

 

http://www.atarimania.com/documents-atari-400-800-xl-xe-books_1_8.html

 

The programs are in an ATR image on this forum some where.

 

Allan

[UNIXcoffee928]

Check out the book "Your Atari Comes Alive"

 

It's the last book in the this page.

 

http://www.atarimani...-books_1_8.html

 

The programs are in an ATR image on this forum some where.

 

Allan

Wow! That book is killer. Wish that I had had it back in the day. I had two of their other ones (Alpha), but I don't remember even hearing about that one. Great Link page, too, Thanks!

 

 

[UNIXcoffee928]

This may be of use to someone... a modern homebrew 6 port A/D unit. Here's the detailed write-up. Looks very easy to build, with a low component count.

 

If you added a little more logic to it, to do the downsample/bit-interpolation before it gets to the Atari, it should leave you with more resources, on the Atari, to perform more complicated effects algorithms.

 

I was also thinking that by strobing redundant audio digitizers, in sequence, on each joystick port, you should be able to achieve a better level of efficiency... Basically, like a striped RAID, except, with the same audio signal being split to each audio digitizer, then being selectively sampled on each joystick port, in sequence. It seems like the most efficient method of getting the data in. Especially with the 400/800 series machines, since they have four joystick ports.

 

I would venture a guess that if you built 2 to four of the latter Antic samplers, wrote a striping driver, and perhaps did the above Hackaday project as a Downsampling Front-End and per-treated your data with it... that you would probably have the Ultimate Atari Sampler. With the right software on the Atari, you could have a dedicated Atari Effects Box that was endlessly tweakable.

 

Anyone know, off-hand, what the calculations would be for the direct digital (already treated by the above A/D Frontend) on the Atari Joystick ports, instead of doing the A/D on the Atari? To re-phrase, "What's the max bps available Digitally per joystick port, and with combinations of joystick ports?". Would there be a benefit to doing the A/D conversion Externally, then just working in the digital domain on the Atari, instead of doing the A/D conversion on the Atari? I would presume that there would be.

[Kernal]

Check out the book "Your Atari Comes Alive"

 

It's the last book in the this page.

 

http://www.atarimania.com/documents-atari-400-800-xl-xe-books_1_8.html

 

The programs are in an ATR image on this forum some where.

 

Allan

where is this atr located, ive searched and cannot find.

[puppetmark]

where is this atr located, ive searched and cannot find.

 

Post number 8:

http://www.atariage.com/forums/topic/124127-looking-for-book-your-atari-comes-alive/page__p__1499944__hl__your%20atari%20comes%20alive__

[Alphasys]

Now, how difficult would it be to make an upgrade to make this possible. I don't know much about electronics, so for me this things are always difficult.

 

You first have to decide which way you want to go. Basically there are 2 ways:

 

1. Samples must be playable on standard Atari without the need of extra hardware.

 

In this case you just need a simple 4-bit A/D converter which you can connect to the cartridge port or a joystick port. It depends on the sampling software you want to use which way to go. Since PoKey can output 4-bits samples anyone can replay them on standard Atari. No separate D/A converter required.

 

 

2. Samples are playable on Atari but requires additional hardware (D/A converter)

 

In this case you need 2 devices. 1 For making samples (A/D) and 1 to replay them (D/A). 8-bits should be enough. More is possible but is of no use. The big disadvantage is that someone who hasn't got the 8-bit D/A converter can't replay the samples (at 8-bit resolution). To replay 8 bit samples on PoKey you need to convert them first (on the fly or at forehand) to a 4-bit or 6-bit resolution.

 

 

I guess Alphasys will jump in here. She wrote several articles about sampling in Atari magazines.

 

Well, I guess I'll add my 2 cents, thanks to the poke by Fox-1 / mnx.

 

Making an A/D convertor for the Atari used to be one of my projects anyways (Alphasys Sample Cartridge).

 

Like anything, there's a myriad of ways to do something. Some are easier than others, and it all depends on where you want to hook it up, and how much speed you want. Sample speed in this case.

 

Using a dedicated chip, like the ADC0804 will provide the most speed, but should be hooked up to the cartridge port. This chip is the "heart" I used in the Alphasys Sample Cartridge, and provides excellent quality with only a few discrete components added. Since it can use the CPU clock as a timing base, and it only takes a few clock-ticks to provide 8-bit resolution, you can sample up to 68kHz with this little thing. All that's needed in discrete components are a few resistors and capacitors doing the following tasks:

 

• Provide a steady voltage reference (typically half the supply voltage or 2.5Volts)
• Noise reduction (to kill static and switching noises generated by the digital circuit)
• Source decoupling (since you generally don't want DC current to leak from/to your input device and mess up your reference level).

I say 68kHz sample speed. This means that the highest "pitch" is actually 34kHz and a 34kHz sinewave would be converted to blockwave. So for a bit of quality sound, pitches higher than 17kHz are not advisable. And these are MAXIMUM values, since the Atari won't be able to keep up with anything higher. Ofcourse, with this type of device, you may still only want to store 4 bits per sample for easy output over a pokey channel. Recording the highest 4 bits is sufficient in this case.

 

Another means of acquiring a digital stream is by using a resistance ladder to drive transistors, which could be connected to one or more joystick ports, depending on output resolution. This is a tricky system though, since it'll basicly output a digital number with an increasing number of bits "turned on" depending on input level, and not a true binary number. (0001 0011 0111 1111) These number would then have to be converted, which limits the sample quality a bit, but with a lookup table, still pretty speedy.

 

The number of states are limited by the number of leads though, so even when 2 joystick ports are used (8 bits in) you'll only achieve a 3-bit sample resolution. (Ralf David's Sound 'n' Sampler used this scheme, and even though it had 4 leads connected to the joystick port, it could therefor only achieve 2 bit resolution.)

 

To achieve a true binary number on the inputs would mean a whole lot more components. For 4-bit resolution, you'll need 16 transistors, 32 highly accurate resistors and a few dozen logic circuits to convert the numbers to their binary representation. This will have to be doubled for any added bit of resolution. A device like that will easily become a huge board.

 

Now for the D/A bit... This is actually a whole lot easier to achieve than A/D.

 

Ofcourse, one could just use a pokey channel in "volume only" mode, and output 4-bit samples over it. By combining all 4 channels, a 6-bit resolution could theoretically be achieved, but the delay in calculating the values, and updating all 4 registers makes for a very sloppy and noisy output. Should not be used in my humble opinion.

 

If one has an 8-bit sampling device, one would of course love to output those too.

 

One way would be, adding a DAC0804 to the ADC0804 circuitry, which would also only need a few extra discrete components to output full 8-bit resolution and awesome sample speed. Since basicly no conversion is needed, it'll output as fast as the CPU can deliver the data, so 68kHz would be possible here as well (256kB would not even hold 4 seconds of sample data though).

 

If you don't want to use the cartridge port for these expansions, a Covox-like device could be attached to 2 joystick ports, to achieve 8-bit D/A conversion as well. A Covox device is basically an R/2R ladder and the switching logic is provided by the PIA. One should however not underestimate the currents involved, and although a PIA has buffered outputs, it's best to use external transistors to do the actual R/2R ladder switching.

 

So... Depending on where you want to hook stuff up, the sample resolution you want, and the sample speed you want to achieve, there are options.

 

If someone is interested in making a cartridge based device with 8-bit resolution, A/D D/A or both, I'll be willing to start shoveling in the basement for my schematic and/or prototype so you have good data to build of. Maybe I can even still find the original PCB layout I used when I made a batch of these things with John Maris for the Halle meeting we attended. The ADC0804 is only one of a myriad of similar devices though, and some may now be easier to come by or cheaper. Should not change the schematic much in any case.

 

Also if someone would like to build a Covox-like device, I'm willing to cook up a schematic of how to make such a device intelligently (and safe for your computer). This kind of device could also be made as a cartridge, but it would then include a PIA chip on the board for the switching logic. This would have the added benefit of having 2 8-bit ports for this purpose, enabling stereo digital output in 8-bit resolution.

 

Of course, none of these devices will work without appropriate software. They are really easy to adress though and the original Alphasys Sample Cartridge was made to be compatible with the Replay cartridge by 2-bit systems. (Although this was an added feature on the prototype and was enabled by switch.)

 

That's my 2 cents to this topic... For the amount of typing, maybe worth 2 dollars.

[UNIXcoffee928]

Wow, thanks! If you could dig up that stuff it would be great!

[Alphasys]

Wow, thanks! If you could dig up that stuff it would be great!

 

I'll have a go at it and see what I can dig up from the dungeon... But what are you most interested in? The Sample Cartridge, or the cartridge based DAC, or the covox type stuff? Or all of the above?

 

Using the same kind of ADC and/or DAC stereo could of course also be a possibility. Using 2 ADC/DAC's would only mean using 2 more addresses, and with a full page at your disposal on the cartridge port, that could even mean full 5.1 Dolby could possibly be achieved, but I shiver at the memory requirements for samples for that.

 

[edit]

 

This won't be an easy task though, since storage space is so limited, it'll literally mean digging through all of what's in there and finding the relevant pieces. Since the PCB layout is only 2 pieces of 4 inch squared paper, I really have to get lucky and find that.

 

While I'm digging in there though, one of the easiest to find will be my 130XE+ bigtower. It'll be the rectangular box that's weighing 140+ lbs... If someone's interested in pictures and explanations for that monstrosity, I'd be happy to oblige as well.

 

Added bonus of that is: It contains the prototype of the sample cartridge.

 

[/edit]

Edited February 25, 2011 by Alphasys

[Mathy]

Hello Alphasys

 

Yes please, tell us more about the 130XE+ bigtower.

 

BTW a couple of the more modern versions of the Dual Pokey upgrades already have Covox (Eastern-European Covox, not American Covox) inside. One of the guys working on such an upgrade is Candle, he's the guy that also does the VBXE PCBs.

 

sincerely

 

Mathy

[Alphasys]

Hello Alphasys

 

Yes please, tell us more about the 130XE+ bigtower.

 

BTW a couple of the more modern versions of the Dual Pokey upgrades already have Covox (Eastern-European Covox, not American Covox) inside. One of the guys working on such an upgrade is Candle, he's the guy that also does the VBXE PCBs.

 

sincerely

 

Mathy

 

Well, a Covox type device is an R/2R ladder, and no matter where you come from, that would still be the same. It's like pigs... No matter if you're European or American, you still get bacon and ham from a pig, and it squeals.

 

But I'll take you up on the request... Won't be easy though. There's so much stuff going on in there... Basically why I haven't taken up the task of repairing it yet. .oO(Outside of not being able to find the right parts yet.) I assure you all, that everything worked before I stupidly infused the baby with 12 volts instead of the regular 5.

 

(Reason for edit: Typo's.)

Edited February 26, 2011 by Alphasys

[Mathy]

Hello Alphasys

 

There was an American company called Covox that sold sound sampling devices for all kinds of 8 bit computers. They regularly advertised in ANALOG Computing and ANTIC. And did this years before the Eastern-Europeans developed their R/2R devices and called this Covox.

 

So American Covox is sound sampling (A2D), Eastern-European Covox is sound creating (D2A).

 

sincerely

 

Mathy

[Blues76]

I have been so busy that I haven't been able to reply to this thread.

AlphaSys, what you posted is very cool stuff...

I'm going to read it and digest it a bit... This topic of doing dsp in the atari is something that I really want to do... kind of a hobby... I have done some DSP in the Texas Instrument TMS320C6713. But I'm no dsp expert and the electronics part is what really kills me, since I don't know much about it... i'm in the cs side.

Anyways, the amount of information provided by AlphaSys is great...

 

Mathy? About the candle, which I purchased a vbxe2 ... what is the upgrade he is working on you

 

In general, I would like a solution that would work as best as possible without me having to do so much electronics...

 

 

GREAT TOPIC!!!!

I have to mention that I started this topic given that there was a similar topic about plugging the guitar into the Atari... so, I just want it to mention that... since I kind of stole the topic, but not in purpose... I want to talk more generic about A/D D/A for the A8

[Blues76]

One way would be, adding a DAC0804 to the ADC0804 circuitry, which would also only need a few extra discrete components to output full 8-bit resolution and awesome sample speed. Since basicly no conversion is needed, it'll output as fast as the CPU can deliver the data, so 68kHz would be possible here as well (256kB would not even hold 4 seconds of sample data though).

 

Alphasys, if you have time, can you give a How to (for non-expert) how to build this circuit... like part numbers and so forth... or anyone else for that matter...

 

thank you

Edited February 27, 2011 by Blues76

[Blues76]

Hello Alphasys

 

Yes please, tell us more about the 130XE+ bigtower.

 

BTW a couple of the more modern versions of the Dual Pokey upgrades already have Covox (Eastern-European Covox, not American Covox) inside. One of the guys working on such an upgrade is Candle, he's the guy that also does the VBXE PCBs.

 

sincerely

 

Mathy

 

Here is the thread that Mathy is talking about (for the one that candle is working on)

http://www.atariage.com/forums/topic/148511-soundboard-gravisultrasound-for-8bit-atari/

[Alphasys]

Alphasys, if you have time, can you give a How to (for non-expert) how to build this circuit... like part numbers and so forth... or anyone else for that matter...

 

thank you

 

Once I've dug up the relevant schematics or hardware (to be able to reproduce the schematic), I'll give all the data you'll need. More than that even. That'll be a thread of its own I guess. I'll have to create a thread just for the 130XE+ in any case. Some of the extensions might need a thread of themselves even. Yeah, it's that much. It wouldn't fit in the original XE housing anymore, even with distance bushings and a gap, it would not fit right.

 

Part numbers may be a problem, except when it comes to IC's. I've noticed that transistor designations are quite different in the US. Other stuff just has values, so that won't be a problem and you can find part numbers for them easily, but the form factor may differ a bit. Won't be a real trouble though.

 

In any case, I intend to explain the workings of the hardware, as well as how to put it together. I'll even throw in some remarks about what would be different when using higher/lower values of components.

 

I'm not an electronics expert though. I only been to a higher technical school for 4 years. In the electronics division. So I'm knowledgeable, yet no expert.

 

[Editreason]Typofixes.[/Editreason]

Edited March 2, 2011 by Alphasys