[Coco] CoCo SDC Preview

[Darren A]

Some of you may recall the FDC emulator project I was working on a
couple years ago.  The goal of that project was to allow DriveWire to
support programs that talked directly to the floppy controller or used
non-standard disk formats.  Unfortunately, I became frustrated by the
growing complexity of the design and set it aside.

Since then I got my first Arduino and began dabbling with the AVR
microcontrollers.  This re-kindled my interest in the FDC emulator, so
I adapted some of the old design to run on an Atmega.  Many had stated
that they don't like having to tether the CoCo to a PC, so the new
design was to target an SD card for storage rather than the DriveWire
server.  The project would allow you to place DSK files onto a
FAT-formatted SD card and access them from the CoCo.  The Atmega,
along with a Xilinx CPLD, provide near-complete emulation of a Tandy
WD17x3-based floppy controller and 2 drives, including HALT, NMI, raw
track operations and the 300 rpm index pulse.  In addition, an
enhanced access mode can be used (with an appropriate driver) for
virtual hard drive images and significantly better performance.

Over the past few weeks I was able to get a PCB fabricated, and with
the generous help of Rogelio Perea I now have 3 functional prototype
boards assembled.  I won't be attending the CoCoFest this weekend, but
the plan is to send one so it will be available for preview.  Stay
tuned…

Darren