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Broadcast - Help needed — Parallax Forums

Broadcast - Help needed

computer guycomputer guy Posts: 1,113
edited 2007-09-16 08:58 in Propeller 1
Do you just need one pin for broadcast mode or do you need all 4?

and what do the settings have to be set to. i.e. pins, mode, broadcast, auralcog?

Thank you smile.gif

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Check out my robot using the propeller robot.tmcp.com.au
If you offer cheap PCB fabrication, perl programming or any other helpful services please email me at.
anthonybmyatt@yahoo.com.au

Post Edited (computer guy) : 9/16/2007 6:09:05 AM GMT

Comments

  • Fred HawkinsFred Hawkins Posts: 997
    edited 2007-09-15 09:16
    interesting robot. How big is it?
  • computer guycomputer guy Posts: 1,113
    edited 2007-09-15 10:09
    45cm long.
    30cm wide.
    16cm tall. (Not including ping sensor on top).

    Thanks for showing interest.
    Am redesigning the site soon. smile.gif

    Know anything about broadcast mode?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Check out my robot using the propeller robot.tmcp.com.au
    If you offer cheap PCB fabrication, perl programming or any other helpful services please email me at.
    anthonybmyatt@yahoo.com.au
  • Fred HawkinsFred Hawkins Posts: 997
    edited 2007-09-15 10:37
    Not a clue.
  • deSilvadeSilva Posts: 2,967
    edited 2007-09-15 11:45
    computer guy said...
    Know anything about broadcast mode?
    Just set it, as described in the TV.SPIN driver, after line 500. Don't forget to set the tv_broadcast frequency
    Using an additional "Aural COG" is a little bit more complicated.
    I have to admit I never did it smile.gif
  • computer guycomputer guy Posts: 1,113
    edited 2007-09-15 12:01
    Yea but do you have to use all 4 dac pins or can you just use the broadcast pin?

    Thank you smile.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Check out my robot using the propeller robot.tmcp.com.au
    If you offer cheap PCB fabrication, perl programming or any other helpful services please email me at.
    anthonybmyatt@yahoo.com.au
  • deSilvadeSilva Posts: 2,967
    edited 2007-09-15 12:03
    There is no broadcast pin.
  • computer guycomputer guy Posts: 1,113
    edited 2007-09-15 12:06
    sorry I got confused with the aural sub carrier pin.

    Thank you smile.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Check out my robot using the propeller robot.tmcp.com.au
    If you offer cheap PCB fabrication, perl programming or any other helpful services please email me at.
    anthonybmyatt@yahoo.com.au
  • deSilvadeSilva Posts: 2,967
    edited 2007-09-15 12:21
    Figure 4 in the datasheet v0.3 explaines a little bit about it.
    A group of 8 pins is used for video, 4 of them are used for baseband, 4 for broadcast. The latter four are the "modulated" former four.

    You control (or suppress) their outputting to the physical pins by "tv_pins" settings.

    You need at least three pins to form 8 voltage levels by an external 1:2:4 current DAC, as the propeller cannot output analogue signals by itself.
  • hippyhippy Posts: 1,981
    edited 2007-09-15 12:55
    I was trying to get UK PAL Broadcast working last night with poor results. I just set Bit 0 of tv_mode, altered tv_broadcast to frequency in MHz, and set tv_hx to 5. On the long-expired VHF channel ( 66_750_00 MHz etc ) I could get a vague signal, enough to see it was transmitting, but nothing on UHF channels ( 823_250_000 MHz etc ). So a few questions, appropriate here -

    1) The aerial is just a piece of wire instead of the cable to TV for baseband, right ?

    2) Does the Propeller / TV.spin support broadcast to UHF channels, > 500 MHz ?

    3) Is using the 5MHz crystal on the Proto Board sufficient for PAL broadcast, or do I need a 4.33<whatever> MHz crystal ?

    4) Has anyone got PAL Broadcast working ?

    I've got TV.spin working with NTSC and PAL to my wired-TV ( very acceptable results for PAL even at 5MHz ), but the portable TV receiver will only accept PAL so it's a bit hard to experiment to take factors out of the equation. PAL CVBS video in works okay but not quite as nicely as on the main TV.
  • Mike GreenMike Green Posts: 23,101
    edited 2007-09-15 13:27
    1) A random piece of wire will work. A tuned antenna of some kind will work better.

    2) The Propeller can't generate signals beyond about 160MHz or so. That covers the lower VHF channels only.

    3) The 5MHz crystal generates lousy signals for NTSC broadcast and I assume the same is true for PAL. You really want a sub-multiple of the broadcast channel frequency, maybe some magic combination of the color burst frequency and the channel frequency. In the USA, a 6MHz crystal works better because the channels are all multiples of 6 MHz. Most sets can lock on quite well to a 60 or 66 MHz carrier.
  • hippyhippy Posts: 1,981
    edited 2007-09-15 15:18
    @ Mike : Thanks.

    2) Yes, it was with hindsight pretty silly of me to expect 500MHz+ !

    3) I may play around with various crystals and try and find a 'sweet channel' later as this really was just playing to hope to impress non-techies - "Propeller TV Station on a Chip".

    The UK abandoned VHF many years ago and UHF is about to get switched off so it's hard to even find TV's with VHF tuners. TV CVBS was what I was really after and that works well enough for me ( 40x16 PAL ). Most impressed.
  • computer guycomputer guy Posts: 1,113
    edited 2007-09-16 05:44
    How do i change from A12, A13, A14 and A15 to A16, A17, A18, A19 For tv output.

    Thank you smile.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Check out my robot using the propeller robot.tmcp.com.au
    If you offer cheap PCB fabrication, perl programming or any other helpful services please email me at.
    anthonybmyatt@yahoo.com.au
  • computer guycomputer guy Posts: 1,113
    edited 2007-09-16 06:25
    Anyone. Please this is urgent. smile.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Check out my robot using the propeller robot.tmcp.com.au
    If you offer cheap PCB fabrication, perl programming or any other helpful services please email me at.
    anthonybmyatt@yahoo.com.au
  • mparkmpark Posts: 1,305
    edited 2007-09-16 08:36
    What to change depends on what you're doing at the moment. If you're using the Parallax TV driver, tv.spin contains this handy table:
    ''  tv_pins
''
''    bits 6..4 select pin group:
''      %000: pins 7..0
''      %001: pins 15..8
''      %010: pins 23..16
''      %011: pins 31..24
''      %100: pins 39..32
''      %101: pins 47..40
''      %110: pins 55..48
''      %111: pins 63..56
''
''    bits 3..0 select pin group mode:
''      %0000: %0000_0111    -                    baseband
''      %0001: %0000_0111    -                    broadcast
''      %0010: %0000_1111    -                    baseband + chroma
''      %0011: %0000_1111    -                    broadcast + aural
''      %0100: %0111_0000    baseband             -
''      %0101: %0111_0000    broadcast            -
''      %0110: %1111_0000    baseband + chroma    -
''      %0111: %1111_0000    broadcast + aural    -
''      %1000: %0111_0111    broadcast            baseband
''      %1001: %0111_0111    baseband             broadcast
''      %1010: %0111_1111    broadcast            baseband + chroma
''      %1011: %0111_1111    baseband             broadcast + aural
''      %1100: %1111_0111    broadcast + aural    baseband
''      %1101: %1111_0111    baseband + chroma    broadcast
''      %1110: %1111_1111    broadcast + aural    baseband + chroma
''      %1111: %1111_1111    baseband + chroma    broadcast + aural
''      -----------------------------------------------------------
''            active pins    top nibble           bottom nibble


    Assuming "A16...A19" means P16...P19, you should set tv_pins to %010_00xx, where xx depends on what combination of broadcast/baseband/chroma/aural you want. HTH.
  • computer guycomputer guy Posts: 1,113
    edited 2007-09-16 08:58
    Thank you smile.gif

    Must have overlooked that table.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Check out my robot using the propeller robot.tmcp.com.au
    If you offer cheap PCB fabrication, perl programming or any other helpful services please email me at.
    anthonybmyatt@yahoo.com.au
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