MSX USB

Guys, love these developments (as I mentioned before I a sure ). I was wondering how far this could go in the future (one that at least sounds great in my mind). I wonder, could we come up with e.g. OPL4 USB, GFX9000 USB? Basically re-implementing these (and other cartridges) to connect over USB to MSX USB where MSX USB would 'translate' and present the devices as their current counterparts would (notably, some I/O, memory space, etc.).

Just thinking out loud here, don't mind me if this is too crazy

Through MSX USB we can communicate with every USB device that is out there. The maximum bandwidth is limited to the speed of an IN/OUT operation at 3,56Mhz. At every IN/OUT with 11 wait states, we can push 1 byte so the theoretical maximum is ~300KB/sec. That's without error-handling, usb protocol handling, interrupts and any other stuff you need to do.

The CH376s module we use supports full-speed USB 2.0 at 12Mbps so that is ~1500KB/sec.

So in terms of bandwidth with simple USB bulktransfers we can do quite a lot. Another CH376s module in Device mode on the other side of the cable with an Arduino could drive the OPL4 and/or GFX9000 and we should be good. We could also do something crazy and emulate the device in another computer.

Sorry popolon_, I missed your question earlier.

Low speed as only device is supported. Behind hub means I have to support multi-TT mode and I haven't figured that out yet. The issue is that the rest of the devices are high speed or faster and the keyboard is the only low speed. Hubs support that via multi-TT mode.

Amazing work S0urceror!

I've been reading this thread and the content of the github last month. So last week I decided to remodel the PCB design to try and make it more DIY-friendly which I attached here hoping this can encourage more people to build their own MSX USB boards. I just finished my layout that I had to route/check by hand because my CAD program (since I don't know how to use Kicad for the time being) is really old and doesn't translate from schematics, etc.

MSX_USB_v1.0_front & back PCB

Main differences between my design and S0urceror's are:

- Due to space constraints this layout uses the PLCC version of the flash memory instead of the PDIP one.
- All sockets and headers now lie on the same side (I had to flip the CH376S header out of necessity).
- All footprints are for through-hole parts (including capacitors).
- The board dimensions are 77,47mm(L)x73,40mm(H). I didn't use the space on the right side (front view) because I noticed that some cartridge enclosures have a screw there.
- Unfortunately, the extra 1cm in height prevents the board to completely fit inside a standard enclosure. Since the top of the cartridge has to be left open in order to access the USB port this shouldn't matter but aesthetically.
- On the other hand, this extra 1cm of the board exposes (on the back side) all the MSX interface signals used in the circuit (plus A14) which may be useful for development, testing and signal analysis, I suppose.

Anyways, I hope you find this alternative convenient. Let me know here or by e-mail what you think of it or if there is something wrong that needs to be corrected since I haven't built my own MSX USB yet. I still can't find the PLD part (and with the current exchange policy of my country it will cost me a fortune if i have to order it from abroad...D'oh!).

Suggestions are always welcome...and long live the MSX!

Wow S0urceror, that's really kind of you.

Thank you for your generosity and for sharing this project with the MSX community.