Hi!
With arduino-vs-msx there are lots of questions:
- first, arduino is no way a slow controller - maybe a little on the RAM side but still 16 mhz and most of commands need a single clock. Multiplication needs 2 clocks - alas even R800 is nowhere near.
- all really interesting "schields" require either i2c or other fast serial interface, which we have on-chip
on arduino (read, microcontroller) with speeds up to 10 mhz or so. Nothing on MSX. Not even ability to transfer data at the rate 
BTW if the qustion is in connecting various hardware, there is UEXT standard (but still requires at least one high speed serial port and 3,3V too)
Hi!
With arduino-vs-msx there are lots of questions:
- first, arduino is no way a slow controller - maybe a little on the RAM side but still 16 mhz and most of commands need a single clock. Multiplication needs 2 clocks - alas even R800 is nowhere near.
Yes, I realize that typical Arduino is 2-3x faster than tR and even slow Arduinos are a bit faster.
- all really interesting "schields" require either i2c or other fast serial interface, which we have on-chip
on arduino (read, microcontroller) with speeds up to 10 mhz or so. Nothing on MSX. Not even ability to transfer data at the rate
I don't understand why I2C would be a problem? Although Arduino boards are fast, most of the other chips are really not that powerful. In slow mode I2C communicates with 10kHz, normal mode is 100kHz and fast mode is 400kHz (Yes, I know modern chips may support also FM+ and HS modes, but they are not very interesting looking from MSX). 10kHz should be doable even with bad code trough joystick port. (Actually I'm planning to test this theory) In I2C master drives the clock, so if MSX is slow -> communication is slow. Not a big deal.
The MSX HAS a SPI interface(open source hardware): http://187.33.0.151//MsxArm/MsxBreakoutFatSpi(the wiki is offline by now). The SPI work with 3.54Mhz so can be fast as LDIR/LDI z80 instruction. So Wiznet W5100 can be connected to MSX breakout board in the serial way and behave as was connected on 8 bits Z80 parallel data bus!!!!
The project is opensource. The main purpose of MSX breakout board(2 flavors: slim/fat) is to interface MSX with MSXARM(http://187.33.0.151//MsxArm/MsxArm). But can be used in another projects too. The breakout board uses a programable logic(CPLD).
unfortunately it is untested. We(I and popolony2k ) are working on a SPI demo.
