[Coco] A Silly MC6847 to HDMI Conversion Idea

David Ladd davidwladd at gmail.com
Sat Aug 6 12:50:35 EDT 2016

On Fri, Aug 5, 2016 at 11:20 AM, 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).

​The other thing that would need to be taken into account is a audio
encoder for converting the analog audio into a digital stream that is
compatible with the HDMI specifications. :)  Though should still be doable

> 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!

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