Super Circus AtariAge (new WIP)

[Andromeda Stardust]

The inexpensive analog to digital conversion method seems like it has to be subject to a lot of variation from one console to the next. The small amount of total rotation used somewhere in the middle (away from the ends) seems to me to be a way to deal with that uncertainty.

 

Okay here's how the ADC conversion on the Atari works:

 

The paddle consists of a potentiometer connected to VCC and input. Inside the console, there is a capacitor connected between the high impedance input and ground. When the console sends a refresh signal to initiate the paddles, this input is dumped to ground by the output of a tri-state buffer. When this refresh signal is released, the pot inside the paddle charges up the capacitor inside the console. This causes the voltage on the input of the logic to climb until reaches a level sufficient to register as high logic. A numerical counter increments a value held in a memory register for each scanline until the paddle input reads high. This value is then stored in memory and used to position a player sprite onscreen.

 

The exact amount of time the paddle takes to register a high input is related to the RC time constant of the circuit. For further reading:

https://en.wikipedia.org/wiki/RC_time_constant

 

Several factors can affect the paddle range including the exact values of the resistance and capacitance, how quickly and whether the reset signal can completely dump the input to zero volts. In the event that the paddle measures zero ohms resistance, the effective time constant is zero and the input will never pull low. For values above a few kohm, the time delay will be fairly linear with resistance up until the point is reached that the total resistance approaches the DC resistance of the capacitor and the input impedance of the digital input. A bigger effect on paddle range and response time will depend upon the exact input voltage at which the chip registers a high logic signal. Suppose a typical logic chip is rated for 5V and low logic signal must be below .8V and high logic is above 2.4V to be in compliance. This means that an invalid logic level input between .8V and 2.4V could register as either low or high and will vary depending upon the exact batch of components, the hysteresis of the input (a low to high transition may occur at a different input voltage level compared to a high to low transition), temperature of the logic chip, and a lot of other factors. So the margin of error for variance between .8V and 2.4V is a factor of up to 3x. So in theory, an Atari with a logic chip input that transtions at .8V would cover a range with three times as much travel compared to an Atari containing a logic chip that transitions at 2.4V. This level of variance could even potentially exist on the same chip on the same Atari, with all four paddles (two paddles per joystick port) showing a slightly different range of movement.

 

An Op Amp or digital comparator would be much better to buffer the input as opposed to using raw digital logic. A reference voltage, say 2.5V, could be generated on the reference input by a simple pair of resistors connected to Ground and VCC, then the paddle line connected to the control input, and the logic transition would occur at exactly the same level on every production console, and each paddle would provide the same range of motion, provided for the component tolerance of the pot and capacitor. The Op Amp has no tri-state buffer but the reset signal could easily be provided by a switching transistor, with a small series shunt resistor to protect it from damage when a zero ohm load (short to VCC) is present. I believe 14-pin DIP quad comparators were available cheaply at the time of manufacture, and Atari could have used these one quad-comparator per console to handle all four paddle inputs, providing quality control to prevent paddle ranges being all over the place from one system to the next, by not relying solely on the transition level of a digital chip not designed to process analog signals.

 

But alas, Atari were cheapskates and cut corners on everything they produced. for instance, the 7800 should never have shipped without the Pokey chip preinstalled (a Pokey in every console is cheaper than including it in every game - no wonder only two games ever used it bitd), but I digress. If every 7800 had built in Pokey, then every 7800 game could have used polyphonic Pokey BGM and only relied on the TIA for explosions and in game sound effects, then the 7800 would have had much better reception among late 80s gamers while still retaining b/c with 2600. Of course, that is not what happened and we cannot rewrite history...

[iesposta]

... so did these work ok?

Works great!

Used both Geminiand Atari Paddles.

 

And chance this "like ballblazer" version with the updated paddle sensitivity will be the version that I purchased already????

[PacManPlus]

Being that I only made this change on Sunday, I don't think so. When I finished this game a few years ago, I used the original Atari paddles. They worked fine. I had no idea that the 'new' AtGames paddles (or the Gemini paddles) had a different range.

[Jinks]

Thats fine by me. Got a ton of atari paddles. Thanks for looking into this!

[Andromeda Stardust]

Being that I only made this change on Sunday, I don't think so. When I finished this game a few years ago, I used the original Atari paddles. They worked fine. I had no idea that the 'new' AtGames paddles (or the Gemini paddles) had a different range.

Wait, the AtGame paddles don't start at zero ohms?

 

It's all good though really. My Atari paddles (0-950ohm) and my custom paddles (0-470 ohm) should do fine hopefully.

[BigO]

Wait, the AtGame paddles don't start at zero ohms?

 

It's all good though really. My Atari paddles (0-950ohm) and my custom paddles (0-470 ohm) should do fine hopefully.

Your extreme of 470 is about the middle of the standard range. I'd be afraid of bumping up against the end of travel on some game somewhere along the line. Do report back on your success with that. I guess if you do run into that, you could add a series resistor (or pot) to bump the maximum end up.

 

At a minimum, you'll have to turn the paddle of your custom controller through more degrees of rotation to get the same level of response as a 1 Megohm paddle controller.

[Andromeda Stardust]

Dang, I forgot the "k" in Kohm.

 

Nearly every game I've encountered for 2600 has used barely a quarter of the full paddle range if that. Bob's Crazy Brix played flawlessly with my custom paddles as well. The stock 1M paddles are too twitchy for my tastes which was why I went with 470k.

 

According to this document, there is a 1800 ohm resistor in series with the TIA input, and a .068 microfarad cap tied between the input and ground.

http://retro.portablesofdoom.org/images/schematics.png

 

Feed 1Mohm and .068uF into a time constant calculator like the one found here:

https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-time-constant

 

This yields a time constant of .068 seconds or roughly four frames of NTSC video, and although the rise time to trigger a high input on the TIA may well be shorter than this if a logic high registers at less than .63 * VCC. I took a stack of vintage Atari paddle games and measured the resistance in ohms at the near and far ends of travel for a variety of games, and none went past approximately 300 kohms before reaching the end of travel, and most sooner than this. So I personally found the usable range of movement on the stock paddles somewhat short which made them feel twitchy. Dividing the total resistance by half gave me a paddle with more usable travel without running out of headroom in most games.

 

So for all intents, it is very likely impossible for a game to read the entire 1Mohm range of a stock paddle while refreshing the signal every frame, and I think it is unlikely that even that a 470kohm would do so. If a game refreshed the paddles once every four frames, it would be possible then and only then to read the entire 1M range of motion. So I think it is safe to say the last half of the paddle travel on the stock paddles almost never gets used by any game.

[MrBeefy]

So I'm dumb with all the technical jargon so I will ask this. Does the Atgames paddles affect gameplay much on a standard atari?

[Andromeda Stardust]

So I'm dumb with all the technical jargon so I will ask this. Does the Atgames paddles affect gameplay much on a standard atari?

In layman's terms, it takes longer than one frame of video to read the entire paddle range, so the vast majority of the paddle range never gets used in any game.

[MrBeefy]

In layman's terms, it takes longer than one frame of video to read the entire paddle range, so the vast majority of the paddle range never gets used in any game.

So you don't have to turn the Atgames paddles as much as the regular ones?

[Andromeda Stardust]

So you don't have to turn the Atgames paddles as much as the regular ones?

I don't know what the range is on the AtGames paddles, but if the pot value is smaller, you turn it more for the same effect. The originals were extremely twitchy for my taste.

[Andromeda Stardust]

Super Circus AtariAge works fine with my custom 470kohm paddles. A bit of bumbling around and hotswapping of the cable in the "unboxing" video due to the fact I had the paddles built into the joystick. Also failure to read the manual before starting the game...

[+GoldenWheels]

Lots of beer and Super Circus last night. Great fun. Even played "Classic" mode for a while.

 

I get some weird static in the audio sometimes though as the game progresses. This is on my new modded system, which hasn't given me any troubles with any other games. And Bentley played and sounded great. Curious.

[AtariBrian]

Lots of beer and Super Circus last night. Great fun. Even played "Classic" mode for a while.

 

I get some weird static in the audio sometimes though as the game progresses. This is on my new modded system, which hasn't given me any troubles with any other games. And Bentley played and sounded great. Curious.

During gameplay or in between boards ?

[+GoldenWheels]

During gameplay or in between boards ?

During gameplay, and it comes and goes, growing a bit loud, then cutting out, then coming back intermittently. All the sound fx seem to be firing fine, and I've had no issues with any other games. No sound issues on menu screen at all.

 

I've rechecked all my connections etc. But again it seems to be just this game.

[Trebor]

During gameplay, and it comes and goes, growing a bit loud, then cutting out, then coming back intermittently. All the sound fx seem to be firing fine, and I've had no issues with any other games. No sound issues on menu screen at all.

I've rechecked all my connections etc. But again it seems to be just this game.

 

That happens with one of my Ballblazer cartridges.

Could be the POKEY chip going or gone bad.

[+GoldenWheels]

 

I have had that happen with one of my Ballblazer cartridges. Could be the POKEY chip going/gone bad.

Well *&^%.

 

Trebor I tried it on my RF only system and though it was hard to get the cord positioned JUST right to not have the normal RF static, I DON'T think it had this audio issue on the RF system. Does that make any sense or point towards anything more?

 

(and normally if I tested that and got those results, I'd blame the system itself or the hookups for sure, but again my modded system has been performing flawlessly with all my other games)

[Trebor]

Well *&^%.

 

Trebor I tried it on my RF only system and though it was hard to get the cord positioned JUST right to not have the normal RF static, I DON'T think it had this audio issue on the RF system. Does that make any sense or point towards anything more?

 

(and normally if I tested that and got those results, I'd blame the system itself or the hookups for sure, but again my modded system has been performing flawlessly with all my other games)

 

I know it may be tedious, but see if definitive consistent or inconsistent results are obtained over several trials.

That may help eliminate possible variables and factors.

 

For instance, in the aforementioned RF system with the cable positioned just right, and it is definitively certain there is no static in any other game, try a half-dozen to dozen trials with SCAA and see if static is ever produced.

 

If you never experience static, it is likely the issue lies elsewhere other than with the cartridge itself; especially so, if you always or usually experience static on the other system with SCAA.

[AtariLeaf]

This is freaking awesome. My favorite 2600 game ported to the 7800

 

MUST. . . OWN. . .THIS. . . CART

 

Quoting my own post from almost seven years ago because now, today, that dream has come true

[CPUWIZ]

 

That happens with one of my Ballblazer cartridges.

Could be the POKEY chip going or gone bad.

 

SCAA carts have Ballblazer's inside, only the ROM was replaced and an inverter added.

[karokoenig]

 

Quoting my own post from almost seven years ago because now, today, that dream has come true

 

...and I've just seen the video you made about it. Now, I don't want to search this whole thread, so someone tell me: When will this be available in the store to us mere mortals? I must have this. F*** the shipping and customs cost.

[Trebor]

...and I've just seen the video you made about it. Now, I don't want to search this whole thread, so someone tell me: When will this be available in the store to us mere mortals? I must have this. F*** the shipping and customs cost.

 

For $30 a year (or $50 for two years)*, you're a Subscriber and not (necessarily) immortal.

 

A mortal who paid $30 for a subscription would already had the option to purchase the game and it would have been sent out to them. An immortal who did not subscribe would be in the same boat as the non-subscribing mortal.

 

Regardless, SCAA and a slew of other titles will be available in the store, for mortals and immortals, *very* soon.

 

*If viewed from a monthly average it's costing an individual only $2.50 a month or less than $2.09 a month.

[karokoenig]

For $30 a year (or $50 for two years)*, you're a Subscriber

 

I was thinking about a subscription anyway, regardless of the benefits - because this is such a great place and it should be supported.

 

So thanks for mentioning this to me. I subscribed.

[Andromeda Stardust]

 

That happens with one of my Ballblazer cartridges.

Could be the POKEY chip going or gone bad.

"replacement chips are available at Mike's Arcade..."

 

Damn, dude, $20...

http://www.mikesarcade.com/cgi-bin/store.pl

 

How many more Ballblazers have to die? Hokey can't come soon enough...

[CPUWIZ]

How many more Ballblazers have to die?

 

All of them.