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Help to add battery backup on pirate Super Mario Kart
http://forums.nesdev.com/viewtopic.php?f=28&t=15777
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Author:  Fisher [ Sun Apr 09, 2017 7:37 pm ]
Post subject:  Help to add battery backup on pirate Super Mario Kart

Hi there!
I got a Pirate, not working, Super Mario Kart.
After doing some tests, I tried to read it. Got only FF's...
So, the ROM was bad. I changed the epoxy blob for a flash and bang! Worked.
I had some very weird rendering issues, wich were surprisingly solved by disconnecting pins 14 and 28 from the bootleg DSP-1. :shock:
So far so good. I noticed it didn't have a save battery.
After adding a 16kb SRAM to the mix, using this circuit as reference I ended with this:
Attachment:
File comment: Back
20170409_204223.jpg
20170409_204223.jpg [ 686.4 KiB | Viewed 1242 times ]

Attachment:
File comment: Front
20170409_204251.jpg
20170409_204251.jpg [ 647.34 KiB | Viewed 1242 times ]

The circuit I used for the battery is:
Code:
                 1K
 -Batt+--->|----/\/\----+--IC Vcc
 |      1N4148          |
GND                     |
       Console's --->|--+
          Vcc     1N4148

Unfortunatelly I don't have a good battery to try it out :-(
Does it makes sense?
I saw in some circuits a transistor on the SRAM's /CS pin but one showed it connected to /RESET pin and other to a specific MAD pin.
Is it really necessary? Won't I be continously losing the saves?

Thanks in advance

Author:  lidnariq [ Sun Apr 09, 2017 7:47 pm ]
Post subject:  Re: Help to add battery backup on pirate Super Mario Kart

Fisher wrote:
Unfortunatelly I don't have a good battery to try it out :-(
You can use 2 or 3 AAs or AAAs instead, they're just bigger.

Author:  Fisher [ Tue Apr 11, 2017 4:08 am ]
Post subject:  Re: Help to add battery backup on pirate Super Mario Kart

lidnariq wrote:
You can use 2 or 3 AAs or AAAs instead, they're just bigger.

Great idea!! That's great for testing!
Unfortunatelly, the AA won't fit on the case, maybe AAA will?

I'm getting 1,5v on the SRAM. Is it fine or I should lower the resistor?
I din't had enough time to test the in-game save functions yet :-(

Author:  lidnariq [ Tue Apr 11, 2017 10:06 am ]
Post subject:  Re: Help to add battery backup on pirate Super Mario Kart

1.5V is definitely low, but first check the voltage across the resistor. You shouldn't be ever drawing more than a couple tens of microamps from the battery when the circuit is operating correctly.

Author:  Fisher [ Wed Apr 12, 2017 8:02 am ]
Post subject:  Re: Help to add battery backup on pirate Super Mario Kart

Checked again, I'm getting 2.34v after the diode ande 1.58v after the resistor.
I could not find the datasheet for this specific SRAM, STK6116. :-(

Author:  lidnariq [ Wed Apr 12, 2017 10:54 am ]
Post subject:  Re: Help to add battery backup on pirate Super Mario Kart

That strongly implies the RAM is not in low-power mode when you're testing.
Fisher wrote:
I saw in some circuits a transistor on the SRAM's /CS pin but one showed it connected to /RESET pin and other to a specific MAD pin.
Is it really necessary? Won't I be continuously losing the saves?
Oh. Yeah, that's why.

It's necessary because otherwise the RAM will draw lots of power and use up all the energy in the battery quite quickly. When the SRAM's /CS pin is high (or +CS pin is low, if it's a RAM that has one), it still retains the contents of memory, it just doesn't draw as much power.

Author:  Fisher [ Thu Apr 13, 2017 4:13 am ]
Post subject:  Re: Help to add battery backup on pirate Super Mario Kart

Great!!
I've put a 10K resistor between /CS and the Batery's diode.
The SRAM's Vcc poped up to 2.38v.
The cicuit ended like this:
Code:
                 10K
              +--/\/\------SRAM /CS
              |   1K
 -Batt+--->|--+--/\/\---+--SRAM Vcc
 |      1N4148          |
GND                     |
       Console's --->|--+
          Vcc     1N4148

Hope it's "undestandeable".
I just don't know how reliable it is, but seems to be enough.
Thank you Lidnariq!! You rock!!! :lol:

PS.: Is it me or this DSP-1 clone is finicky?
It took a while to start the game, all I was getting was the Nintendo logo and the boot sound.
At first I tought it was the clock generator, but them I found a broken track on the demux.
But even this wasn't enough to boot.

Curiously, I added a LED to the DSP-1's /CS line and it booted!!
WEEEEIRD!! I played for a while and removed the LED. It stayed fine.
Other day I just melted the solder on the crystal's pins and it booted.
I also needed to cut 2 pins for it to render the graphics fine. :shock:
These pins seemed to be already cut from the begining, and I tought it was someone trying to fix it before me. :oops:
I'll just assemble it and don't touch!!

Author:  mikejmoffitt [ Thu Apr 13, 2017 5:09 pm ]
Post subject:  Re: Help to add battery backup on pirate Super Mario Kart

On my real cart, if there's a connection issue, I'll get the Nintendo logo (and coin sound I think), but it'll halt at that point.

Author:  Fisher [ Thu Apr 13, 2017 5:26 pm ]
Post subject:  Re: Help to add battery backup on pirate Super Mario Kart

You mean bad cartridge contact?
I cleaned it with an eraser and was still getting the same thing as you said, the Nintendo logo and the coin sound.
A interesting thing I saw is that if I connect the GameGenie and don't input any code the game passes the coin sound, but the road gets all green and the drivers just get stuck.

The pinout seems to be exactly the same, except that pins 14 and 28 need to stay unconnected, else I get something like this:
Attachment:
File comment: DSP-1 bug
20170408_155811.jpg
20170408_155811.jpg [ 861.52 KiB | Viewed 1071 times ]

That's weird!!
Looks like the DSP-1 isn't totally active.

For what I have seem (and read) latelly, you can expect almost anything from pirates. :mrgreen:

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