- Wed Sep 24, 2008 5:19 pm
#55912
Hi Mike,
Yes, I'm using output compare modules for dot clock and hsync. Vsync is computed off of hsync. In principle I should be able to get up to about 4MHz but for some reason I lose sync above about 500 kHz at the moment. I seem to be caught in a frustrating catch where a low frequency dot clock is stable but looks bad, and the high frequency dot clock won't sync. Feels like there ought to be a happy compromise here somewhere, but it's not proving easy to find!
Update: I updated all of the sync signals (dotclock, hsync, vsync and DE) to use output compare units, and can now happily sync up to 4MHz or so. Of course I don't have any hope of being able to generate rgb data at that rate, but it was an interesting exercise. Sync at slower speeds seems to be a bit hit and miss - a lot of speeds won't sync and you have to explore around a bit to find ones that do. At about 1MHz the display doesn't look too bad for strong colours, and I might try and see how far I can get with this. For some reason mid-tones suffer very badly from flicker. Here's a new pic just for fun:
James.
Yes, I'm using output compare modules for dot clock and hsync. Vsync is computed off of hsync. In principle I should be able to get up to about 4MHz but for some reason I lose sync above about 500 kHz at the moment. I seem to be caught in a frustrating catch where a low frequency dot clock is stable but looks bad, and the high frequency dot clock won't sync. Feels like there ought to be a happy compromise here somewhere, but it's not proving easy to find!
Update: I updated all of the sync signals (dotclock, hsync, vsync and DE) to use output compare units, and can now happily sync up to 4MHz or so. Of course I don't have any hope of being able to generate rgb data at that rate, but it was an interesting exercise. Sync at slower speeds seems to be a bit hit and miss - a lot of speeds won't sync and you have to explore around a bit to find ones that do. At about 1MHz the display doesn't look too bad for strong colours, and I might try and see how far I can get with this. For some reason mid-tones suffer very badly from flicker. Here's a new pic just for fun:
James.