[Coco] A Silly MC6847 to HDMI Conversion Idea

Al Hartman alhartman6 at verizon.net
Fri Aug 5 12:49:29 EDT 2016

With all that said, why not use the existing (or soon to be existing) Coco to VGA adapter and simply use a VGA to HDMI converter?

It might not be as nice as a dedicated solution, but it would give a better signal than composite, or a composite to VGA/HDMI/etc adapter.

-[ Al ]-
On 8/5/2016 12:21:06 PM, Mark J. Blair <nf6x at nf6x.net> wrote:
In my mental image of how I would hypothetically design an HDMI-capable MC6847 emulation, it's miniaturized down to a module the same length and width as the 40 pin DIP socket it plugs into, with a mini HDMI connector on one of the narrow ends. I think this would be very challenging to say the least, but not necessarily unachievable with off-the-shelf components. I picture it as a self-contained, drop-in replacement, though I guess it would need at least one flying lead to pick up the sound signal. I haven't done the detailed analysis yet to determine if I could make the two regulators needed for the Xilinx FPGAs I'm familiar with small enough, how much circuitry I'd need off the FPGA for electrical interfacing, and whether I could cram the necessary functionality into the small, inexpensive FPGAs that I would hope to use (one of the bottom two options in the Spartan 6 line).

My desired mechanical size constraint would require one of the smaller BGA package options to fit in the board width, and it may not be routable within the design rules of the likes of OSH Park. It's been long enough since I worked with a 0.8mm pitch BGA that I don't recall the trace, space, via and hole sizes needed to escape one. I spent lots of time at 0.4mm pitch in my last job, and at 0.4mm pitch I wouldn't want to pay for the PCB out of my own pocket. :)

I would see the selling price of this hypothetical doodad being north of $100, and I'm skeptical that anybody would want to pay for one. Thus, I'm sticking to my assertion that this idea is silly!

Mark J. Blair, NF6X

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