NTSC and S-Video out at same time
LouM
Posts: 1
I'm just starting to look at the propeller to generate NTSC and S-Video in an ATE rack I'm developing. Is it possible to have both being generated by the same propeller chip, coming out of course on different I/O pins. Would this require a special driver or would I be able to use the TV.spin driver for both outputs. I just need to generate simple color bars or even the graphics palette display would work.
Comments
To configure S-video electrically, you build the reference video circuit, only don't connect start_pin + 3 to the other pins. It is the color only pin, and needs to not be part of the DAC that forms the core video circuit. The same resistor is used for chroma in both the S-video and Composite circuit.
From there, you can just have two video signal COGs scan whatever buffer you setup, each outputting their signal. If you've got the room, two different buffers can be used, or the display can be generated dynamically.
Most of the existing graphics drivers can be modified to use different sets of pins, pointing at the same screen buffer.
You will need to make sure the chroma on start_pin + 3 bit is set for the S-video COG. Look at the VCFG data sheet, and driver COG setup code for this change.
The Parallax driver should work great. I think you will need to duplicate the block of passed values, and COGNEW the TV COG twice, passing each one a different block of values, most of which will be the same, but for the pins and video mode settings.
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Post Edited (potatohead) : 11/17/2009 4:35:35 PM GMT
Not as perfect as separate feeds or buffered arrangements but then the signal isn't suppose to be "broadcast grade" with calibrated levels SC/H relationship etc ....
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