[Coco] [Fwd: Re: CoCo 3 FPGA? (Really long message)]

[Mark McDougall]

> From: Becker, Gary <Gary.Becker at amd.com>



> As I have already mentioned, I have no capabilities to adapt floppy

> drives into the system. 


I'm currently working on a (Commodore 64) 1541 implementation in an FPGA,
that will interface to some sort of external storage media. I have also,
in the past, done a simple WD1793 implementation that interfaces to serial
flash.

My intention is to provide 'sub-cores' if you like of disk controller and
disk media interface IP that can be chopped-and-changed to provide a
variety of options for various 8-bit computers.

Interfacing to a real floppy is also on my list...


> This pulse stream runs fast

> enough where a simple low pass filter should be able to convert it to

> audio. This filter is the additional circuitry needed. I will be

> building prototype circuitry soon for testing.


I've had reasonable success in the past with a Sigma-Delta DAC and
external RC low-pass - not that I've been concerned with high-fidelity
output! ;) May I suggest you package the DAC at the top-level, to expose
the 6-bit digital stream on other platforms such as the DE1/2 and/or
NanoBoard which have on-board audio DACs.


> I am sorry to say, I have no plans to support the standard CoCo

> joysticks. This joystick uses a DAC to sense the position of the

> joystick. As I mentioned in the last paragraph, the response was

> unacceptable in my past tests. 


I'm surprised you didn't get acceptable results - or did you stick with
the resistor-ladder ADC? I would think there's plenty of cheap ADC chips
out there that would be more than adequate for the task?


> The different type of joystick will be software

> compatible with the original joystick, but with only three positions

> vertical, up, middle, and down, and three positions horizontal, right,

> middle, and left. 


That's OK for games that are, in effect, using the joystick as a digital
joystick, but I suspect not suitable for all games?!?


> What I would prefer

> not to happen is someone package this system up for mass market

> consumption similar to the $25 arcade games based on the Commodore 64

> platform that you see at Wal-Mart.


With all due respect, I think the C64-on-a-joystick market is _way_ larger
than a Coco-on-a-joystick market. In any case, an FPGA-based design is
simply not economical - it would have to be an ASIC design and you're
talking _big_ bucks there.

IMHO you should be more concerned that someone will package a 'games
development system' or similar like the XGameStation, and bundle your Coco
design with it.

Regards,

-- 

|              Mark McDougall                | "Electrical Engineers do it

|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"