Utilize the expansion bus on the TG-16/PC-Engine found here PC Engine + Shuttle Expansion Port
Using the Digital Ports VD0-VD8 which include:
HSn Horizontal Sync
VSn Vertical Sync
DCK Dot/Pixel Clock (5.36 / 7.16 / 10.73 MHz)
VS Unknown
XNMI - Non-maskable interrupt to CPU
XRD - Read from CPU
VD1 - VD8 ViDeo Bus bits 1-8, directly connected to the video encoder (HuSomething)
VD0-VD3 = four bit pixel value
VD4-VD7 = four bit palette value
SPBG = high for sprite/border pixels, low for background pixels (for genlock, or LaserActive use?)
Upscale (line double) through an FPGA to 720P HDMI output.
Also integration of Analog audio into the HDMI output would be nice as well
I'm currently working on a similar project for a Neo-Geo system, but is much easier as RGB and Audio can be found in digital format before being processed by DAC's.
Thanks,
James Fischer
Retro-Rabbit