[Coco] RS232 Schematics, was DriveWire survey

[CoCoList for Color Computer Enthusiasts]

>> That is actually similar to how we do this thing called the "Becker
>> interface" which you might have seen mentioned here.. Its implemented in
>> Gary Becker's FPGA coco and in all 3 of the main coco emulators now.
Its
>> just two bytes or registers I guess if I'm getting the words right.. one
>> for read/write and one for status.  The emulator or FPGA basically does
the
>> role of the clpd if I'm following things.  Anything you write to ff40
goes
>> "out" and reading ff40 gives you the next byte coming "in".  Non zero in
>> ff41 means theres a byte ready to read, and that's all there is to it.  I
>> think I have the addresses right but there is a conflict with them anyway
>> so forget that bit.
>
> Yes, this a simple "interface"  How does one tell the "host" what it
wants to do?  Is there a command byte, data byte structure for this
"Becker" interface?

If we're talking about the data going in/out, right now we have variants of
Disk BASIC and OS9 drivers that use the Becker interface in place of the
bitbanger for DriveWire.  The FPGA connects the outside of the Becker
inteface to a serial line and the emulators use a TCP socket, both then
connect to a DriveWire server.  Its just faster drivewire.

While you could just run DriveWire on a pi connected to the clpd and have
something that works very quickly, I think it would be well worth exploring
something rather different in the long term.  With a high speed / low
overhead interface (opposite of what DW is designed for) and a tiny
dedicated computer (again, not what DW was designed for) there are lots of
new possibilities.   You could expose the USB, make the SD card slot a
dedicated drive, allow the coco to directly access the networking on the
pi, use the HDMI out as a terminal display, all kinds of awesome stuff!  I
would be quite motivated to help create software to enable all of that.
Some of what we've learned in DriveWire would help, we are pretty good at
multiplexing dozens of data streams over one pipe.  But really its a much
broader opportunity and deserves a better platform than DW would provide.