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Date Posted: 17:15:50 01/28/02 Mon
Author: star
Subject: Re: Need expert help please!!!!!
In reply to: Potter 's message, "Re: Need expert help please!!!!!" on 17:46:17 01/25/02 Fri

>Sounds like it's not locking at all - just feeding the
>scrambled signal straight through as intended. The
>big white bar is probably a strong inverted hsync - if
>it is you should be able to see the colour burst just
>after it.
>Removing the SETMODE routine would prevent locking as
>this routine counts the number of good/bad consecutive
>frames and makes the decision to descramble or not.
>Your problem may be the polarity of the edges your
>code looks for to find specific events EG if the VBI
>is inverted the LOCKON routine needs to look for a
>mirror image of events (PED instead of NED & vice
>versa). A close examination with a cro should reveal
>what you require.
>
>>
>>Hi expert programming guy! Has you know, i'm in
>>Canada, Montreal. The only way i got the
>>PIC16F84A-20/p Locking on scramble channel with the
>>3Chip Board was by removing SETMODE section in Rev1tb
>>file. The only problem, it dosen't synchronise the
>>horizontal and vertical good. Everytime you change
>>channel, the big white bar in the vertical is never at
>>the same place in the screen, and horizontal is a bit
>>wavy on top. The burst is not very nice too. Any
>>suggestion?
>>Thanks

Hi Gary,

I was working on the 3-chip a few months ago, had to stop due to lack of time. I live in Montreal as well and have been experimenting with the board. I have a board that works and the schematic mathces the original 3-chip from magicboxes.
I have access to some pretty cool scopes and was analyzing the NTSC signal. It seems as though the VBI is messed up. The time interval of which it takes up is still there but the signal looks nothing like a NTSC VBI. Therefore the SETMODE in the code will not work due to errors in not finding Line 6. Since the VBI is messed up, there is no guarantee that you could lock on anything in that interval accuratley for each frame.
As well the HSYNCs are lowered and video inversion is also used. As far as I can tell the code for the 3-chip should find the syncs correctly, its the VBI that is troubling me. Is there any other way I can find where I am in the frame. I have thought of counting syncs from the time the VBI ends or perhaps the last HSYNC in each frame may be sampled.
Either way, this VBI must be overcome in order to succeed. Any hints from TOM or anyone else would be much appreciated. If I do get anywhere and figure it out, I'll be posting it pronto...
See ya,
Star

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