Re: apple 2 usb

["David Wilson" <mcs6502@gmail.com>]

Mark McDougall wrote:
> Michael J. Mahon wrote:
> > In the case of the keyboard, for example, 8-bit Apple programs
> > expect the keyboard ASCII and any-key-down signals to appear at
> > specific memory-mapped addresses.  That is not an easy adaptation
> > for any peripheral card.
>
> A few pages of VHDL is sufficient - I've already done it to convert input
> from a PS2 keyboard to emulate an AY3600 (the keyboard chip in a IIe) within
> an FPGA implementation of an Apple... would fit in a small CPLD or PIC.

The trick is, how does the card interoperate with the existing
keyboard? Does it disable it or try and work alongside it? You also
have to make it work on the II/II+, the IIe and the IIgs if you do not
want to fragment the market still further. Each of these systems has
differences in keyboard handling. A slot based card cannot disable the
onboard keyboard on a IIe (and only on a I/II+ if the USER1 jumper is
soldered) [this is based on 5min reading of Understanding the Apple II
an Apple IIe books but appears to be correct].

The most flexible design for a USB card would be to make it appear as a
SmartPort controller as this protocol already supports block (disklike)
and character (keyboard/mice/etc) devices. Unfortunately there has
never been a SmartPort character device (AFAIK) and no existing program
is going to look for a mouse or a keyboard on a SmartPort. This would
not be a problem for GS/OS with its loadable drivers but would be a
killer for the II/II+/IIe market.