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I purchased two of the new WonderSwan FlashMastas when they were in stock last week, for the purpose of doing some R&D work. They arrived today and work fine in my WonderSwan Color, but they do not appear to function in the classic black-and-white WonderSwan. They just show a screen filled with black pixels.
I'm borrowing a friend's WonderSwan to get homebrew development off the ground, and it does work on the B/W model. I understand that the units from this last batch were a different revision, v5.2, and the one from my friend is v5.1. Did something change in the revision that broke or removed compatibility with the black-and-white WonderSwan?
It might be something that I can fix on my end, in which case I'm open to ideas. I have a support ticket open about it, but if someone knows what's going on, that would help get things resolved and make everyone's lives easier. Thanks in advance!
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For the moment, try this workaround on the B&W.
Insert an official game cartridge (any cart that’ll boot properly).
Hold Start when booting (or whatever it is to enter the bios menu, not 100% sure offhand).
While in the bios menu, swap to the Flash Masta cart. Then exit the bios menu. I think the Flash Masta will boot.
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I can give more info later. I’m just on my phone now and about to eat dinner.
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(02-28-2021, 11:25 AM)Flavor Wrote: I can give more info later. I’m just on my phone now and about to eat dinner.
I just got my Flashmasta today and I have an old BW Wonderswan. I actually got it to boot up once - although I have no idea how or why. Tonight, I added a bunch more roms and added the menu rom for slot 1 and couldn't get it going and found this. I'm curious if there's any other options other than the cart swap.
I actually bought this WS brand new in Japan in 2004 for like $20 and barely used it, so I'm glad I can finally use it either way 
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(02-28-2021, 11:24 AM)Flavor Wrote: For the moment, try this workaround on the B&W.
This is really clever and absolutely did the trick. You're my hero! Now I'm kind of ashamed I didn't think of this...
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(02-28-2021, 11:25 AM)Flavor Wrote: I can give more info later.
Are you able to provide more information? I'm eager to get to the bottom of the issue. From what I could learn discussing this with some others, it appears that the changes made between v5.1 and v5.2 broke compatibility with the black-and-white model WonderSwan, in that it no longer passes the boot-time security check. I'm hoping I might be able to fix this on my end, but that may not be possible depending on what needs to be done.
Surely this wasn't intentional. It would be a big step backwards for the new version to be less capable than the old version.
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03-02-2021, 09:13 AM
(This post was last modified: 03-02-2021, 09:13 AM by Flavor.)
Yes, I can elaborate. I can't get a whole lot of time for this sort of thing on the weekends, but I wanted to give you a quick workaround at the time.
Actually, when we say "v5.1" or "v5.2" on the circuit board, that's _just_ the board. In fact, the changes between those versions are inconsequential.
The change that matters here is the switch from a nvSRAM chip ("CY14B104LA" made by Cypress) to a MRAM chip ("MR2A08ACYS35" made by Everspin). All of Everspin's documentation shows the part as a direct drop-in replacement for the Cypress chip. We should be able to use them interchangeably according to their documentation. The Everspin chips are better for a handfull of reasons, so we bought some, tested them, and implemented them. In fact, some "v5.1" boards have the Everspin chip on them.
After we shipped this most recent batch of WS Flash Masta carts, we found out that they have bootup problems on the B&W Monochrome Wonderswan. The "problem" is actually complex, but it has to do with the power supply boost conversion on the B&W WS. We've been researching this for the past week or two.
As you know, the WS uses a single AA (1.5v) battery. The WS boosts this voltage to 3.3v. The WS Color and SwanCrystal have different boost circuitry than the B&W. Presumably, Bandai realized that improving this section of the system was needed, so they "fixed" it in the newer models. Also, the B&W model's design relies more on larger electrolytic capacitors. If you know anything about old electronics and video game hardware, you know that electrolytic caps get worse over time. That may play into this.
When the Color WS models boot up, they somewhat instantly go from 0 to 3.3v for the cartridge's power supply.
When the B&W WS boots up, it "kinda slowly" gives the cartridge voltage that ramps up over time. (Slowly is like a half second when using the Everspin chip.)
The Everspin chip reacts poorly to this interim voltage, and it causes a (very temporary) extra draw on the AA battery. If this is powered by something else that can supply more power, the system will boot up fine.
The reason that the "swap trick" works is that they system is already powered up, and swapping cartridges will supply the 3.3v "instantly" instead of during system power-up.
The Cypress chip doesn't exhibit this behavior. After a bunch of research and data gathering, we reached out to Everspin's technical support. They have been trying to help us, but they seem somewhat baffled themselves. They want to blame the power supply (the WS itself), but the fact remains that their chip is behaving differently than the Cypress chip that they claim to be a replacement for.
All of this is worsened by two things for us.
1) We've shipped a batch+ of these carts with that chip.
2) We've already re-ordered more of these chips for future batches.
So, we'd like to come up with a workaround, but we haven't found anything that can be fixed with a firmware update or anything like that. We did find a workaround to make the cart boot up, but it's not something that an end user could implement.
I am currently waiting for a response (that may turn into further conversation) with Everspin. I really hope we can get that chip working. Until we know more, I can't give any sort of new workaround, fix, update, or even guesses for the solution.
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Perfect, thanks for your explanation, and thank you for being so forthcoming with this information. This will be very helpful to an associate of mine who is tinkering with FPGA stuff.
I won't worry about the B/W compatibility issue. I can use the cartridge-swap workaround to get it to run, which is what I need for my work. Best wishes in getting things sorted out on your end--sounds like a rough situation all around.
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It seems this does eventually boot in a B/W WonderSwan after several seconds. I don't know if it's harmful to the display or not, though.
It's not letting me attach a short video file to this post. Basically when I turn it on, the screen goes black, which gradually fades to white over the course of about 20 seconds. At the 22 second mark, the system boots at the Bandai logo screen and then the FlashMasta menu loads up.
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(03-02-2021, 01:48 PM)Danno Wrote: It seems this does eventually boot in a B/W WonderSwan after several seconds. I don't know if it's harmful to the display or not, though.
It's not letting me attach a short video file to this post. Basically when I turn it on, the screen goes black, which gradually fades to white over the course of about 20 seconds. At the 22 second mark, the system boots at the Bandai logo screen and then the FlashMasta menu loads up.
What battery are you using? Is it just a regular AA or something else?
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