SNES2Atari Adaptor - Programming Interface

[+wavemotion]

Greetings programs.

 

So for emulation purposes, I tried (unsuccessfully), to understand how the interface to the SNES2Atari adaptor works. My rough guess from looking at the 7800basic assembly is that it's done serially - clocking in and out bits to the adaptor to figure out what buttons are being pressed. I would imagine similar to how the SaveKey is interfaced. But it was a bit too much and overloaded my feeble circuits. I'm going to have another look at the code today with two cups of coffee to see if that helps improve my understanding.

 

In the meantime - is there a guide or topic (Google failed me) that explains it at a level where mere mortals can understand it?

 

I tried to find the code in A7800 but came up short there too. 

 

Thanks in advance for any help!

 

[The Usotsuki]

Given the similarity to the NES controller - which is serial - that makes sense.

[RevEng]

Documenting the SNES2Atari is still on my TO-DO list. I'll try to get it out this weekend.  Presently there's no support in A7800, and there likely won''t be in the short term.

 

You've grokked the driver correctly - it's a serial device, and the button data is latched and clocked in. I've attached @Danjovic's driver, (it's his design) which is simpler and has better comments than the 7800basic one.

 

 

[removed. The driver is now available at the wiki]

[+wavemotion]

No rush @RevEng - that driver was commented well enough that I think I can manage! 

[+wavemotion]

@RevEng I've got most of it worked out... question: is it expected that the SNES2Atari adaptor will only be used on Port 2?  Are there expectations for using it on Port 1 as well?  Will games generally use the auto-detection on both ports?

 

I'm excited to offer this in the future as a controller choice. A7800DS has the standard classic Nintendo controller layout which is identical to the SNES (D-Pad, ABXY, LSH, RSH, Start and Select) so this works out perfectly.

 

[RevEng]

That is a stunning development.

 

For various reasons, I don't think you can count on the snes2atari being in a particular port. e.g. If a game supports atarivox and snes2atari, then the snes2atari will almost certainly be expected to be plugged into port 1.

 

Does A7800DS pull and use controller info from the a78 header?

 

[+wavemotion]

24 minutes ago, RevEng said:

Does A7800DS pull and use controller info from the a78 header?

Yes - though it only supports a few of the controller types right now. I'll be looking for 11 = SNES2Atari for both ports ... however, my emulator only really supports a single controller (being a single-player handheld) so ...  The user can override the controller type on a per-game basis.

 

Let me ask the question another way... if I only (for now) supported SNES2Atari on Port1... would that likely be usable on games supporting the controller scheme?

 

Lastly - the driver provided is well documented but is for Port 2. I assume for Port 1 it's just re-purposing the the UP/DN pins for P1 (instead of P2) and using the low bit in INPT4 instead of INPT5 as the serial shift feedback to the 6502 program?

[RevEng]

 

44 minutes ago, llabnip said:

Let me ask the question another way... if I only (for now) supported SNES2Atari on Port1... would that likely be usable on games supporting the controller scheme?

Yeah, but there may be exceptions. Sometimes authors put optional controllers on port 2, to avoid making the user unplug their main controller from the game. Having an oddball controller plugged into port 1 also makes it difficult or impossible to navigate flashcart menus, depending on the cart.

 

44 minutes ago, llabnip said:

Lastly - the driver provided is well documented but is for Port 2. I assume for Port 1 it's just re-purposing the the UP/DN pins for P1 (instead of P2) and using the low bit in INPT4 instead of INPT5 as the serial shift feedback to the 6502 program?

Yup to all of that, with the slight correction that it's the high-bit of INPT4/5 we're dealing with.

 

[+wavemotion]

It's working! Thanks again, @RevEng for the detailed responses and help with this.

 

Mike even went out of his way to provide me a little test program to help me get my logic right. The 7800 Community is lucky to have him!

 

[+mksmith]

39 minutes ago, llabnip said:

It's working! Thanks again, @RevEng for the detailed responses and help with this.

 

Mike even went out of his way to provide me a little test program to help me get my logic right. The 7800 Community is lucky to have him!

 

Well done! And yes we are very lucky to have Mike in our community 👏👏👏

[RevEng]

Thanks for the kind words, guys!

[ZippyOasys]

Does this work with the 2600+?