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Stable Composite Video? — Parallax Forums

Stable Composite Video?

Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
edited 2007-05-25 15:54 in Propeller 1
I've been looking a various TV video drivers that have been used here, and notice that many seem to produce slightly shaky video (jittering text). The only exception to this has been the HSS demos, which use a 38x7 text output. Is there a reason for this, or am I the only one experiencing this? (Is it time to ditch my TV? [noparse]:)[/noparse] )

Oldbitcollector

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The comments and code above are proof that a million monkeys with a million propeller chips *could* write Shakespeare!

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2007-05-23 03:07
    The primary TV driver used, TV.spin, seems to be "rock steady" for me on the Hydra, Protoboard, Demo Board, and even with the beta Spin Stamp on a BOE. I've only used it with the 2.5" LCD display and a 32" standard television set.
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2007-05-23 03:15
    I've continued searching for an answer and turned up a few interesting items in this thread...
    http://forums.parallax.com/showthread.php?p=587524

    Seems to be an issue with interlace mode... Shame too, but as soon as I disabled it and changed
    Chip's driver to 38x7, it became rock solid as well. (Although, the 7th drops just a little into th bottom of the screen)

    Personally, I vote for a little less and rock solid video.. [noparse]:)[/noparse]

    Or is this something that could be solved with a few more pins?

    Oldbitcollector

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    The comments and code above are proof that a million monkeys with a million propeller chips *could* write Shakespeare!
  • kenmackenmac Posts: 96
    edited 2007-05-23 10:32
    Hi folks,
    Just joined today, although I've been a "reader" of the threads for some time now.

    I've been using a USB propstick on my own protoboard, wired for video as per the Parallax Demo Board circuit.
    Yesterday I tried the TV Terminal program, using a 7" LCD PAL screen.
    The results were similar to those discussed in this thread - not very steady, I suppose "jittery" is the best description.
    I had put that aside for further investigation later, but then I spotted this thread on the forum.
    I haven't tried it on a larger TV yet.

    kenmac
  • bambinobambino Posts: 789
    edited 2007-05-23 14:32
    Ditto,

    I have gotten the TVgrapics to work on the Spin Stamp, but no luck with TV Terminal on it, The protoboard, PE Kit, or a homeBrew I have since fried.

    To much side stepping of the Picture. I suspect in my case it's the TV I'm using.(Possibly will have another to practice on this week).

    PS. The one that did work, didn't until I adjusted the Mode settings dealing with Chroma. It is still Greek to me.
  • Dennis FerronDennis Ferron Posts: 480
    edited 2007-05-24 00:32
    I've used the standard Propeller TV text and graphics demos with my suitcase computer on a big CRT, a tiny 7" LCD tv, and on a projector, and never noticed a problem on any of them. If some people are having trouble with jitter, I guess the first thing to determine is whether the problem lies with certain TV's or certain propeller boards. I'm using the same circuit as the propeller demo board, but I've built it on a breadboard. (I kept the breadboard wiring very neat though.)
  • rjo_rjo_ Posts: 1,825
    edited 2007-05-25 05:50
    Oldbitcollector,

    The first thing that I tried to solder... in about 50 years... was a small board to implement the video circuit... apparently solder has some resistance because it didn't work... at all.
    Next thing I tried was replacing the resistors with potentiometers...and the sky opened up and the angels danced[noparse]:)[/noparse].

    Rich
  • Graham StablerGraham Stabler Posts: 2,510
    edited 2007-05-25 10:21
    Solder has negligible resistance so it is much more likely that you had a dry joint or the circuit wired up incorrectly, or the wrong resistor values.

    Graham
  • bambinobambino Posts: 789
    edited 2007-05-25 12:44
    I think I can hear angels singing! Oh where's my bread board? Why didn't I think of that? Doh!
  • rjo_rjo_ Posts: 1,825
    edited 2007-05-25 15:46
    Graham

    The resistors had the right values... the wiring was correct... and where I live there isn't a dry joint in the area...

    It had to be the solder... I didn't weigh it... but per pound solder must have some resistance.

    Since then I got a couple of proto boards... and I successfully put all the parts on. So, I'm thinking I'll try it again.

    Rich
  • rjo_rjo_ Posts: 1,825
    edited 2007-05-25 15:54
    Graham...

    I had everything laid out end to end...about an 1 1/2 inches per "trace" ... so I supposed it might have been picking up interference.

    Rich
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