Time Base Correction + Backpack

tprson56

Hello all,

I am new to the forums but not to the propeller chip. I am an engineer at a small robotics R&D shop where we use the propeller for all kinds of different tasks. We have come across a new problem lately that I am trying to find a relatively cheap and simple way of solving. The new OEM TFT monitor modules we have been testing out all go to a blue or black screen when they loose the video sync signal from the RF receiver for even a millisecond. This is very annoying as it takes a few seconds for the screen logic to resync to the signal and display the picture. When dealing with multi-path this can occur quite frequently and render the video useless. However with our old monitor setups when the sync signal was lost the screen would display static and then back to the picture as soon as the sync signal was found again.

We are wondering if the propeller based backpack board is capable of doing this. I am by no means a video signal expert, but as I know it in order to over lay video on the screen(which the backpack is capable of) you must sync the two signals together. So if the backpack is capable of doing this would it be capable of operating as a Time Base Correction unit on the cheap? Does anybody have any ideas on how this might be accomplished?

frank freedman

One question is whether the monitor will go off with loss of only one or both H or V sync. If is will only go standby for loss of say V sync, could it be possible to pick off the real sync signal as it goes to the monitor and apply the sync to a freq to voltage converter (or just take the sync direct into a freq to voltage conversion ckt) and feed the voltage level out into a VFO adjusted to track the original sync signal. Add in a sample and hold keyed by a pixel clock for H sync or Hsync for V sync VFO and send that output to the monitor sync inputs. Feed through would require a possible switch path between real sync and VFO or input sync to f2v2f to output sync could always provide a sync signal to the monitor sync input. The question on these two ways to do it, does the sync signal switch fast enough for the monitor to stay alive in switch mode sync or is the delay introduced by the f2v2f circuit low enough that there are no noticable distortions due to the delay the inline sync method would introduce.

I have seen variations of this in some imaging systems.