Making a cart from scratch...

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the_wizard_666
Posts: 62
Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

I'm kind of confused now. The spot on the board for the VRC chips is a DIP40 socket. If the chips aren't DIP40, what will I need to do to put them in the socket? Am I correct in assuming I'd have to map the pins from the chip onto the board somehow? Or am I missing something here?

Either way, I'll read over the documents. I'm in no real hurry, as the boards haven't arrived yet, so I've got plenty of time to figure this all out.
lidnariq
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Re: Making a cart from scratch...

Post by lidnariq »

You're unfortunately exactly right: the only things that are already correct for the sockets on that board are the real VRC2, VRC4, and the 3rd party clones I mentioned.

Anything else will require some kind of adapter board to use instead.
the_wizard_666
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Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

Well, sounds like I'll just have to cross that bridge when I come to it. And not order the VRC boards again unless I can figure out a way to do it that won't take forever to do :P
the_wizard_666
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Re: Making a cart from scratch...

Post by the_wizard_666 »

Alright, so most of my supplies have arrived, and I tried out an NROM for a start, since the boards are simple enough. However, I encountered an issue - when booting the cart, it comes up with a scrambled start. There are a few possible issues that I can see. I'm using a system with the lockout disabled, so that shouldn't be an issue (I'll test that chip once I know the game is working otherwise). I figure those with more experience can rule out issues on this list for me so I can narrow down my diagnostic focus.

Possibility 1: The CHR chip
Simply put, I used an 8KB chip (M27C64A), but the board specifies a 16, 32, or 64 KB chip (M27C128/M27C256/MC27C512). I have the other chips, so that isn't an issue, I would just prefer to use the smallest possible, and figured it should be fine. If this is the likely issue, I'll just switch the chip and do the double-write thing on an M27C128 instead. But again, if the C64A is compatible, I'd rather use that.

Possibility 2: The Capacitor
Basically, my capacitors haven't arrived yet. The only capacitor slot on the board is located above the lockout. I assumed the capacitor is for the lockout chip, which should make it irrelevant when the system's lockout is disabled, but again, being a newbie to this, my assumption may very well be incorrect. Regardless, the cap will be installed as soon as they arrive, so if that's the issue, it'll be solved in a matter of days.

Possibility 3: Bad burn
I checked and rechecked the chips before installation, but there's always a possibility of a bad burn, either from a bad ROM or an issue with the chip itself. It may well have been user error with the burner too, as I'm learning on the fly with it.

Possibility 4: Accidental solder error
Again, I checked the board thoroughly to ensure that I didn't accidentally solder two contacts together that shouldn't be soldered. Pretty sure this isn't the issue, but I do know it can cause this issue to occur, so I'm not going to rule it out just yet, unless something else is a better fit.

Possibility 5: Something completely different
Again, I'm new to this. Maybe there's something I'm overlooking.

And before you suggest the mirroring pads, I soldered the right two together. The ROM uses vertical mirroring, and I soldered the middle and V pads together. I'm leaning toward the first two possibilities as the most likely issues - I just figured I should verify them as likely causes before I start going crazy taking things apart again. Thanks for the help!
lidnariq
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Re: Making a cart from scratch...

Post by lidnariq »

the_wizard_666 wrote: Wed Mar 24, 2021 4:14 pm when booting the cart, it comes up with a scrambled start.
Does it remain scrambled? Describe the nature of the scrambled? Are things - within your ability to tell - the right color but the wrong texture?
Possibility 1: The CHR chip
Simply put, I used an 8KB chip (M27C64A), but the board specifies a 16, 32, or 64 KB chip (M27C128/M27C256/MC27C512). I have the other chips, so that isn't an issue, I would just prefer to use the smallest possible, and figured it should be fine. If this is the likely issue, I'll just switch the chip and do the double-write thing on an M27C128 instead. But again, if the C64A is compatible, I'd rather use that.
Check the speeds on your CHR. Really small ones might be too slow. I think the threshold should be 280ns...

Otherwise, all the 28-pin UVEPROMs should be interchangeable.
Possibility 2: The Capacitor
Basically, my capacitors haven't arrived yet. The only capacitor slot on the board is located above the lockout. I assumed the capacitor is for the lockout chip, which should make it irrelevant when the system's lockout is disabled, but again, being a newbie to this, my assumption may very well be incorrect. Regardless, the cap will be installed as soon as they arrive, so if that's the issue, it'll be solved in a matter of days.
No, it's actually to make things behave more nearly correctly. Chips are designed to assume fairly constant supply, and capacitors help with that.
The ROM uses vertical mirroring, and I soldered the middle and V pads together.
Be careful! Nintendo's PCBs used V=layout, and so do Muramasa's, and as far as I can tell only emulators use V=mirroring.
the_wizard_666
Posts: 62
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Re: Making a cart from scratch...

Post by the_wizard_666 »

lidnariq wrote: Wed Mar 24, 2021 4:34 pm
the_wizard_666 wrote: Wed Mar 24, 2021 4:14 pm when booting the cart, it comes up with a scrambled start.
Does it remain scrambled? Describe the nature of the scrambled? Are things - within your ability to tell - the right color but the wrong texture?
Possibility 1: The CHR chip
Simply put, I used an 8KB chip (M27C64A), but the board specifies a 16, 32, or 64 KB chip (M27C128/M27C256/MC27C512). I have the other chips, so that isn't an issue, I would just prefer to use the smallest possible, and figured it should be fine. If this is the likely issue, I'll just switch the chip and do the double-write thing on an M27C128 instead. But again, if the C64A is compatible, I'd rather use that.
Check the speeds on your CHR. Really small ones might be too slow. I think the threshold should be 280ns...

Otherwise, all the 28-pin UVEPROMs should be interchangeable.
Possibility 2: The Capacitor
Basically, my capacitors haven't arrived yet. The only capacitor slot on the board is located above the lockout. I assumed the capacitor is for the lockout chip, which should make it irrelevant when the system's lockout is disabled, but again, being a newbie to this, my assumption may very well be incorrect. Regardless, the cap will be installed as soon as they arrive, so if that's the issue, it'll be solved in a matter of days.
No, it's actually to make things behave more nearly correctly. Chips are designed to assume fairly constant supply, and capacitors help with that.
The ROM uses vertical mirroring, and I soldered the middle and V pads together.
Be careful! Nintendo's PCBs used V=layout, and so do Muramasa's, and as far as I can tell only emulators use V=mirroring.
The scrambling comes up as basically just gibberish. It doesn't look like anything is correctly loading in any capacity. There's no blinking or anything like that, it's just a static scramble screen with multiple colours.

Looks like the chip is 100ns. Probably not a speed issue. I have noticed I get a device ID error on those chips (all of them, not just the one), so THAT could be a problem as well. I disabled the check because I'm 100% sure I input everything correctly, but that could still potentially be the problem. I updated the firmware when I installed the program, but there may still be an update I'm unaware of, so I'm looking into that as well.

As for the mirroring, you may be right that few, if any, retail games would use V mirroring, but the fact that this is a homebrew title would preclude that necessity. Famirom outputs the following:

iNES ver.: 1.0
platform: NES
mapper: 0
mirroring: Vertical
prg size: 32KB (256kb)
chr size: 8KB (64kb)
prg ram: not specified
battery: no
trained: no
TV system: NTSC
boards: (NROM [NROM])
CRC32
prg: 687B6D44
chr: E2DC50D3
data: D78C3026
file: 30FE2AF8

Mirroring is definitely vertical, not horizontal.
Joe
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Re: Making a cart from scratch...

Post by Joe »

"Vertical mirroring" is the same as "horizontal layout". "Horizontal mirroring" is the same as "vertical layout".

If your boards follow the "layout" terminology instead of the "mirroring" terminology, then you would need to solder the "H" pad for vertical mirroring.
the_wizard_666
Posts: 62
Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

Joe wrote: Wed Mar 24, 2021 6:05 pm "Vertical mirroring" is the same as "horizontal layout". "Horizontal mirroring" is the same as "vertical layout".

If your boards follow the "layout" terminology instead of the "mirroring" terminology, then you would need to solder the "H" pad for vertical mirroring.
Well, I reread the previous post. I'll try it out with the H pad instead of the V pad and will let you know the result.
the_wizard_666
Posts: 62
Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

Well, we have a partial success. The visuals are still scrambled to hell, but now if I press start the audio starts, so the program itself is working fine. All I changed was the V pad is now disconnected and the H pad is connected to the middle. Could the missing capacitor be the culprit? Or is there a possibility there's something else wrong?
lidnariq
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Re: Making a cart from scratch...

Post by lidnariq »

The capacitor will probably help, but you probably also have some other problem. Do any individual pixels flicker? Or is the image stable and wrong?
the_wizard_666
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Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

lidnariq wrote: Wed Mar 24, 2021 6:47 pm The capacitor will probably help, but you probably also have some other problem. Do any individual pixels flicker? Or is the image stable and wrong?
There's flashing corresponding to where there are flashes on the title screen, and when starting the game the same thing - there are flashes roughly corresponding to where there is flashing on screen. Additionally, there is no title music, but after pressing start the in-game music plays.
lidnariq
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Location: Seattle

Re: Making a cart from scratch...

Post by lidnariq »

Sounds like the ROM is probably all that's wrong any more. What's all the specific text on the 27C64 you're using?
the_wizard_666
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Re: Making a cart from scratch...

Post by the_wizard_666 »

lidnariq wrote: Wed Mar 24, 2021 7:00 pm Sounds like the ROM is probably all that's wrong any more. What's all the specific text on the 27C64 you're using?
M27C64A
12F1 L
96003 V5
MYS 96 534

Brand is ST
lidnariq
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Re: Making a cart from scratch...

Post by lidnariq »

This is using a MiniPro to program them? Did it report anything during verification?

When it complained about having the wrong device ID, what specifically did it report?
the_wizard_666
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Re: Making a cart from scratch...

Post by the_wizard_666 »

Here's the output window when I try and verify the chip:
Capture.PNG
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