[Coco] DriveWire survey

[CoCoList for Color Computer Enthusiasts]

On May 11, 2014 1:39 AM, "CoCoList for Color Computer Enthusiasts" <
coco at maltedmedia.com> wrote:

>
> You'll have to pardon me for being new to CoCo, but I see two places
where an "interface" would be useful.
>
> 1) the serial port on the Coco.
> 2) the expansion port on the Coco.
>
> I'm suggesting a WiFi interface that can:
>
> a) run standalone, connected only to the serial port (DriveWire-ish)
> b) run plugged into the Coco or a MultiPack (and would also connect to
the serial port)
>
> The box would have a complete TCP/IP stack onboard, along with what is
needed for Wifi (or Ethernet, if that's of interest)
>
> The questions I have are:
>
> Was the Coco serial port used for anything in the day?

Printing primarily.  It was quite limited for telecom use but it was
possible.  Most people used an add on serial pak with a uart for that,
though.

> On the expansion port, what types of interfaces would be candidates for
Wifi capability (I assume there was a UGART cart available, FDD controller,
HDD?, anything else?)

There were/are all those plus some sound devices, x10 controller, weird
drawing pad thing called xpad, probably more.  If its important I'm sure
there is a comprehensive list somewhere.

Something that severely limits us with DriveWire now is that the bitbanger
serial port must be polled for input, and doing that at 115kbps requires
100% CPU with interrupts masked.  This has the consequence that all I/o has
to be initiated by the coco, no way for the server to tell the coco when
data is coming in.  The DW driver has to constantly poll the server to make
bidirectional I/o work.  It tries to adapt in real time to be efficient but
its just not a good situation. If there was a buffer/UART on your device
and it could raise the interrupt line when ready, that would open the door
to vastly improved performance.

-Aaron