 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Microcontroller and PC projects : When composite video - isn’t....
| Author | Message | ||||
Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9063 |
Hi folks. 
Does the VT100 ASCII terminal generate true compliant composite, or does it generate a fake kind of composite? I ask as I have a 7" flat panel here I was trying to use with it, and it looks like there is MAJOR vertical sync problems - the cursor shows up on about 20 screen lines, blinking on and off as it should. This LCD does not like the taste of the VT100, cos I have tried it on my projector and TV in the other room, and they work fine, and the VT100 shows up there exactly as it should. I will get another LCD - they are cheap as chips, but I was wondering just how true to the standard is the composite output. I have the VT100 set to PAL. If I feed a DVD player or VCR(both of which are set for PAL output) into this LCD, the picture is fine, so this LCD is being picky, but it made me wonder why. I will try setting the VT100 to NTSC and see if that helps. EDIT: LCD does not like PAL from VT100, but seems happy enough with NTSC from VT100. LCD is auto-switching type, but perhaps it needs the colour(chroma) signal to do that? Without it, it selects the wrong video standard.... Smoke makes things work. When the smoke gets out, it stops! |
||||
Geoffg Guru  Joined: 06/06/2011 Location: AustraliaPosts: 3165 |
It is close but not 100%. The main difference is that "true composite" sends half a horiz scan line at the end of a vertical frame so that you have an interlaced image. The VT100 does not do this but it does send an extra line at the end of each odd frame to keep the timing correct. Geoff Geoff Graham - http://geoffg.net |
||||
| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9063 |
Wow, that was a fast reply, Geoff.... 
Thanks. Smoke makes things work. When the smoke gets out, it stops! |
||||
palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1802 |
I have two panels working OK with Geoff's VT100 terminal. Paul. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
||||
| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9063 |
Yes indeed. I fully acknowledge that it is just my "Picky" panel in this case, but it made me curious as to what the difference in the signal was, that would make my panel dislike it as much as it does. Those cheap reversing camera panels are a dime a dozen on eBay, so it is not a concern. Smoke makes things work. When the smoke gets out, it stops! |
||||
| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1802 |
@ Grogster, Thinking back I had a similar problem at first and discovered it was the 12 volt supply I was using to power the panel. A 12v gel cell fixed it. Paul. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
||||
 Print this page |
