Messages

1

EverDrive N8 / Re: Famicom version to NES?

« on: January 09, 2019, 12:36 AM »

It works, and the store even sells a nice converter for putting it into a NES shell. But one thing to keep in mind is that if you want to use the USB port, it's soldered in a place which won't allow you to insert the cart in a front-loader without a game genie (or similar adapter) stuck in-between.

Wish I would have thought of that, but the game genie solution isn't too horrible...

2

EverDrive N8 / Re: Mapper 30 Support?

« on: February 04, 2018, 05:45 PM »

Because mapper30 is just a variation on the mapper2 that Krikzz has released source for, getting the basic functionality is quite easy. Here's my quick attempt at it:
https://drive.google.com/open?id=15es4lWuMfDyo1jY6S8fAZwv5NAhh7juB

It doesn't yet support re-writing the PRG-ROM though. I think that might be doable, but would probably require an OS update to actually get data back to the .nes file, unless the everdrive already supports storing PRG memory to disk. (but I think that's only supported for the battery-ram, and .fds files?)

3

EverDrive N8 / Re: How do the map_cfg bits map to iNES header flags?

« on: February 04, 2018, 01:31 AM »

Nevermind, just found it's actually all in the source to edn8usb: map_cfg is just the bits of byte 6, as I had guessed. Just had a verilog n00b mistake in the code...   

It works and support both variants of mapper30 just fine AFAICT. Here's the new version of it:
https://drive.google.com/open?id=15es4lWuMfDyo1jY6S8fAZwv5NAhh7juB

However, it doesn't yet support writing to the PRG-ROM, as a real Mapper30 cartridge would. I don't think it would be too hard to add that feature to the verilog code, at least if I skip the erase and assume the game will always write every single byte rather than relying on erased sectors having a starting value. (and come to think of it, relying on erased sectors working correctly could be a simple copy-protection scheme for any homebrew developer worried about piracy... )

But for such a write feature to actually be useful, I think the Everdrive file system handle would need to be updated to support writing the ROM back to the sd card. Could this feature be added in the near future?

4

EverDrive N8 / How do the map_cfg bits map to iNES header flags?

« on: February 03, 2018, 09:03 PM »

I'm trying to implement mapper30 support on the Everdrive N8, as a "Hello world" project to start off my mapper development ambitions - and give people the opportunity to run roms like Troll Burner on an Everdrive. It's pretty much a straight copy-n-paste of the mapper2 example provided by Krikzz, so not much complication getting the basic functionality working.

But I am running into trouble with my "stretch goal" to supporting both variants:
1) The original mapper30, which can be hardwired for either vertical/horizontal mirroring or single-screen mirroring
2) The infinitelives variation, which replaces all of that with 4-screen mirroring (using the last 8kB of the 32kB CHR-RAM for 4-screen mirroring)

The current proposal on nesdev for how to support both of these variants in one mapper number is to re-interpret bit3,bit0 (4-screen flag, mirroring-flag) of byte 6 in the iNES header as follows:
00: horizontal mirroring
01: vertical mirroring
10: 4-screen mirroring
11: single-screen mirroring

(this is not yet implemented even in most emulators but discussed in this thread: http://forums.nesdev.com/viewtopic.php?f=3&t=14725)

From the mapper examples, I was easily able to see that map_cfg[0] usually denotes mirroring control, but I have not found any definition of the rest of map_cfg's layout. And I'm not even 100% sure there is a 1-to-1 mapping between both the relevant iNES mirroring flags and the map_cfg register.

So at the moment, I can only create a mapper30 file that is hard-coded to either use map_cfg[0] for horizontal/vertical mirroring selection, or hard-coded to do 4-screen mirroring, which is a bit of a shame.

Could anyone tell me a bit about exactly how the map_cfg register maps to the iNES mirroring flags?

5

EverDrive N8 / How

« on: February 01, 2018, 03:00 AM »

Hi,

I figured I would finally try some mapper development on the Everdrive N8. But it seems I am stuck at the very first stage: Obtaining the software.

Namely, I thought I would use the official "Quartus II web edition software" from Altera which I found here: https://www.altera.com/downloads/software/quartus-ii-we/91sp2.html

But to even be able to download the software, the altera.com website requires me to register an account. And when I try to do this, the form always errors saying "Sorry. An error occurred when creating your account. Please try again.", with no information on what particular field it is refusing to parse.

Would anyone here happen to know how to get past that broken web form? Or if there is any suitable alternative software that can create bitfiles for the CycloneII FPGA in the Everdrive N8?

// Michel