Showing the video sync (LM1881 app)
Javalin
Posts: 892
All,
Been playing with video and trying to get overlay working.· But I've been having issues with (a) understanding the pulse setups and (b) trying to guess whats going on.
So I though'd i'd write a bit of ASM to help me understand this.
The attached code counts and times the pulses from the LM1881 video sync seperator chip, stores in RAM and then debug's it out to a PC terminal (hypertrm etc).· You'll need a video source and the LM1881 chip Comp-Sync and V-Sync pins connected to propeller pins 14,15 respectivly.
It works well on my PAL video output, showing the timings' which corespond to the diagrams in the LM1881 datasheet.· I'd be interested to know if anybody with a NTSC setup also gets correct readings?
Just a bit of fun,
James
Been playing with video and trying to get overlay working.· But I've been having issues with (a) understanding the pulse setups and (b) trying to guess whats going on.
So I though'd i'd write a bit of ASM to help me understand this.
The attached code counts and times the pulses from the LM1881 video sync seperator chip, stores in RAM and then debug's it out to a PC terminal (hypertrm etc).· You'll need a video source and the LM1881 chip Comp-Sync and V-Sync pins connected to propeller pins 14,15 respectivly.
It works well on my PAL video output, showing the timings' which corespond to the diagrams in the LM1881 datasheet.· I'd be interested to know if anybody with a NTSC setup also gets correct readings?
Just a bit of fun,
James
