[Coco] RS232 Schematics, was DriveWire survey

[CoCoList for Color Computer Enthusiasts]

On 5/11/2014 11:20 AM, CoCoList for Color Computer Enthusiasts wrote:
> For a new piece of hardware for connectivity options, would it not be
> useful to do it via USB?  In that fashion, with appropriate firmware, it
> could facilitate access to a variety of devices (ethernet, wifi, bluetooth,
> video, audio, joypads, memory/disks, etc) and adjust it's visibility to the
> Coco (ports, address space, etc) accordingly (via software)?
>
> Those of us without a multi-pak would appreciate a single cart with
> multiple (future potential) options, in a single cart.
>
> Wifi dongle plugged in - treat as serial (etc) to a Drivewire server, flash
> memory - treat as FDC (like CocoSDC) and/or HDD (like the SuperIDE), USB
> mouse - treat as a hires joystick adapter, video adapter - treat as a
> WordPak+, audio adapter - treat as an Orch90...  upon startup, the
> cartridge could (eventually) query the USB for device(s) and allow the
> enduser to choose functionality of the device(s), or even allow for direct
> access via user supplied additions to the firmware, onscreen, before
> returning control to normally scheduled programming ;)
The main problem with USB as a "super interface" is the driver aspect.  
It's not an unworkable idea, but having given some thought to things 
over the night and day, it is apparent that all such solutions will 
require one component:

a Coco bus to uC/CPU bridge.

When the Coco (or any system, for that matter) goes to read a byte from 
the bus, the data needs to be there already, because an ARM or AVR won't 
have time to go get it and stuff it onto the bus for the read, unless 
there is a wait state, and wait states are no fun.

I'm still noodling how to do that, as each legacy interface expects 
things in a certain way.

Jim