Demo Vision
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Re: Demo Vision
Is it practical to swap game boys between the two consoles without soldering? The moving noise in the center (what should be GB tiles) makes me wonder if that connection is robust.
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Re: Demo Vision
Hi Lidnariq -
Hmmm - what do you mean exactly? Swapping gameboys... I do have two functional GB units with the ribbon cable - they both work with the NTSC model however do the same thing with the EUR version. It is absolutely possible something is broken with the board or ribbon cable port. I am still thinking the issue is either A) the PAL unit needs a proper TV or even better Power converter, or B) one of the chips is damaged on the PAL unit. Swapping some of the chips may rule this out. I am reluctant to swap the soldered crystal however would be a last resort haha.
Adam
Hmmm - what do you mean exactly? Swapping gameboys... I do have two functional GB units with the ribbon cable - they both work with the NTSC model however do the same thing with the EUR version. It is absolutely possible something is broken with the board or ribbon cable port. I am still thinking the issue is either A) the PAL unit needs a proper TV or even better Power converter, or B) one of the chips is damaged on the PAL unit. Swapping some of the chips may rule this out. I am reluctant to swap the soldered crystal however would be a last resort haha.
Adam
Re: Demo Vision
Yeah, don't do any soldering until we've exhausted everything else.
Re: Demo Vision
You do not need to change the crystal. The device being PAL is not your problem, and obviously PAL systems do work because they manufactured and sold them this way. You only need to change the crystal if you need this to be an NTSC console.
1. Try swapping your Game Boys. This should be trivial; they are connected by a cable. I don't think this is the problem.
2. I'm 90% sure your problem is that you need to reset the system twice. This is in the instructions. Toggling the power switch ("power cycling") is not resetting. I don't know if there is a reset button, but there is supposed to be a reset cable. Since it seems like you probably don't have a reset cable, try bridging the two pins of the reset port twice.
3. If you are able to write a new ROM, replace U39 with a new ROM containing the rev B firmware. I have extracted the PRG ROM data from that linked ROM and attached it below. It is 8 KiB, and if your ROM is larger than that, it must be repeated up to size. The rev B firmware performs the boot process twice, and for reasons I cannot yet explain, this apparently works around whatever issue requires one or two resets.
Your symptoms match the symptoms I've seen that were solved by resetting. Furthermore, the fact that the image is changing indicates that the Game Boy is connected well enough to trigger interrupts on the Demo Boy, telling it to swap frame buffers.
1. Try swapping your Game Boys. This should be trivial; they are connected by a cable. I don't think this is the problem.
2. I'm 90% sure your problem is that you need to reset the system twice. This is in the instructions. Toggling the power switch ("power cycling") is not resetting. I don't know if there is a reset button, but there is supposed to be a reset cable. Since it seems like you probably don't have a reset cable, try bridging the two pins of the reset port twice.
3. If you are able to write a new ROM, replace U39 with a new ROM containing the rev B firmware. I have extracted the PRG ROM data from that linked ROM and attached it below. It is 8 KiB, and if your ROM is larger than that, it must be repeated up to size. The rev B firmware performs the boot process twice, and for reasons I cannot yet explain, this apparently works around whatever issue requires one or two resets.
Your symptoms match the symptoms I've seen that were solved by resetting. Furthermore, the fact that the image is changing indicates that the Game Boy is connected well enough to trigger interrupts on the Demo Boy, telling it to swap frame buffers.
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Re: Demo Vision
I had something quite similar with EU DBII, have you tried using the reset port (short the 2 pins of P3 for a second)?
The power switch reset method did worked on my EU DBII, but I had to have a timing to get it working-ish, when the use of the reset line worked everytime.
The power switch reset method did worked on my EU DBII, but I had to have a timing to get it working-ish, when the use of the reset line worked everytime.
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- Joined: Thu Jan 26, 2023 1:16 pm
Re: Demo Vision
FYI - resetting the device twice or any number of times unfortunately did NOT work. I did this by using a multimeter to connect the two ' reset' pins that would normally attach to the reset button on the kiosk. When i do this - the system resets. Sometimes when resetting i just get a grey screen, however typically I just get the standard light green with dark noise/square in the middle.
Next step for me will be to swap chips. If that works... I will burn some chips.
Again huge thanks to this group - and everyone's assistance so far!
Adam
Next step for me will be to swap chips. If that works... I will burn some chips.
Again huge thanks to this group - and everyone's assistance so far!
Adam
Re: Demo Vision
The revision A PAL has been dumped and is available here. I think revision A is the only revision of the PAL. Hopefully this can help fill in some of the holes in our understanding, particularly of the IRQ, though this is a bit lower level than what I'm skilled at.
Re: Demo Vision
It's not a dump of the PAL fusemap, so it might be incomplete. Also, how do input/output pins map to bits in the file?
Re: Demo Vision
While it's true that the included PAL dump is a full combinatorial dump of all the inputs to all the outputs, inspecting said dump establishes that the fusemap does not use any of the feedback paths - each output is just a function of the instant inputs.
The dump is the pins more-or-less in order, here's the plan that Voodooween said he used to dump it:
Separately, I've already analyzed that dump, and arrived at the conclusion that the behavior is:
The dump is the pins more-or-less in order, here's the plan that Voodooween said he used to dump it:
Separately, I've already analyzed that dump, and arrived at the conclusion that the behavior is: