8-bit Computer TV Channel Use

Alan Hightower alan at alanlee.org
Mon May 25 07:46:58 CDT 2015


On 2015-05-23 11:24, Mark J. Blair wrote: 

> In the middle will be some FPGA to perform any necessary magic. I've been looking at a prohibitively expensive ($115) one that has enough dual-port RAM blocks to support a frame buffer. I need to see if I can push the frame buffer out into external RAM in order to move to a cheaper FPGA. It would be ideal if the video parameters could be figure out automagically, but I have a feeling there will be a need for user-adjusted parameters, and possibly even loading up different FPGA programming to handle some odd-ball signal.
> Output would be HDMI, at 1080p. Are other interfaces and/or resolutions desirable? I'd like to keep it as feature-simple as practical.

OMG, stop. Google "Composite to HDMI" and you will find hundreds of low
cost boxes that do this. Hopefully one of them will work for you. I was
going to do your idea for C64s long ago until I realized there's no way
I can do it nearly as cheap as Mr. Wong in his apartment in Shenzhen,

However if you really want to pursue your idea "because it is fun for
you", I suggest looking at the Lattice XO2 Control Development Kit
(novel idea of OpenLDI in/out + LPDDR2), the Digilent Atlys board
(Spartan 6 + dual direct TMDS in&out), or NeTV (Marvell SoC + Spartan 6
w/ dual direct TMDS) as starting points. 

You don't even need a full frame buffer if you need to scale. If the
frame rates match, you can just store one line if you need to horizontal
stretch and/or line-double, or three lines if you want to perform
multi-tap vertical scaling. All HDMI TVs (at least in North America)
support 480i however you generally have to pixel double per the CEA-861
standard to have enough clocks in the HBI/VBI to pass audio. 



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