[Coco] An FPGA GIME project, and CoCo FPGA Experimenter's Board

[Zippster]

A little bit of my planning for the board...

So far for features to be included on the board I have…

Fully implemented bi-directional interface to the CoCo through the cartridge slot,
		with FPGA control of level-shifter ICs where useful
	- 42 pins

VGA output, 3 bits per channel resistor DAC
	- 11 I/O pins

RS232 I/O via Maxim 3238 serial transceiver
	- 9 I/O pins

Stereo Sound out jack - 2 channel PWM
	- 2 I/O pins

ADC input - ADC128S022CIMTX (Texas Instruments)
	- 4 I/O pins

SDRAM (32MB)
	- 39 I/Opins

2x 16-bit shifters (32 pins) + shifter controls (8 pins)
		(for TTL level inputs or LVTTL outputs)
	- 40 I/O pins

~25 pins left - (will likely end up being unshifted general I/O)

A few ideas I’ve had include…

Implementing a hardware sound function via PWM, that as has been suggested before, 
would allow for sampled sounds to be played on cue from the CPU without tying it up for actual
sound generation.  Basically you'd upload your sounds to the hardware sound system when 
loading your program code and then just call a sound as needed.

Implementing a WordPak style interface allowing for an 80 column or greater text output
on a second display (VGA) for text-intensive things.  Of course there’s the possibility of
implementing graphics modes as well.

It was suggested by Camillus to use a layout for some of the I/O headers that will be compatible
with Arduino style shields.  I think this is a good idea, and I’ll try to do that.

I realize a project like this will probably only be of interest to a few people other than myself,
but I think it may be an important one as it could lead to a few different hardware options for
the CoCo.  At the very least it should be an excellent learning tool for interfacing FPGAs
to an 8-bit microcomputer.   :)

So I’ve put a page here I’ll post updates to for those interested…
<https://sites.google.com/site/thezippsterzone/coco-fpga-experimenter-s-board <https://sites.google.com/site/thezippsterzone/coco-fpga-experimenter-s-board>>

- Ed



> On Oct 22, 2015, at 8:36 PM, Zippster <zippster278 at gmail.com> wrote:
> 
> I think I will do the Experimenter’s board first.  It shouldn’t take too long,
> will give me some practice with the BGA packages, and may prove to be a
> useful tool in developing the GIME project.
> 
> I think I have the interface to the CoCo port (level shifters) all figured out.
> A couple of things I want to put on the board for sure will be a VGA port, and sound
> out (resistor DACs).  So it could be configured as a video card similar to a
> WordPak, or a sound board (among a multitude of other things).
> 
> It looks like the interface to the cart port will use up 42 FPGA pins, so there
> will be 130+ for other stuff!  I think you could probably make the ultimate I/O board
> out of this thing.  :)
> 
> - Ed
>