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VGA and Prop Demo Board — Parallax Forums

VGA and Prop Demo Board

PliersPliers Posts: 280
edited 2010-12-10 21:13 in Propeller 1
Is it normal not to be able to down load a program to the Prop Demo Board while a VGA monitor is connected to that board?

To make it work, I have to disconnect the VGA monitor, down load the program, then reconnect the VGA.

VGA demo programs from parallax.
No other hardware connected to the Prop Demo Board.

Comments

  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-12-10 06:02
    The DemoBoard has the VGA pin 9 connected to +5 Volts, although it serves no useful perpose for a Prop board. The volts are there so that the PC can power up an EEPROM in the monitor, so that PnP on the PC can identify the monitors capabilities (Old leads had that pin missing).
    Some cheap leads would short it out, but that would shutdown the DemoBoard perminantly (they do not do PCs much good either)

    Downloads need the reset line to be cycled, I wonder if the VGA lead is somehow messing with that. Apart from the above I dont see how that could be.

    (I only have homemade DemoBoard clones, with non-USB interfaces. I never connect the VGA pin 9)
  • wjsteelewjsteele Posts: 697
    edited 2010-12-10 07:26
    Interesting... I don't see that problem. Can you swap VGA monitors to see if it is just that one?
  • PliersPliers Posts: 280
    edited 2010-12-10 07:56
    I tried another monitor, still the same problem.

    I am guessing this is not normal.
  • Cluso99Cluso99 Posts: 18,069
    edited 2010-12-10 14:19
    I have not seen this problem either.
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-12-10 14:24
    I know that it is a probably a pet hate of mine but I was trying to think what on the VGA could affect the loading of programs. It still think it could be due to power or earthings.
  • Dr_AculaDr_Acula Posts: 5,484
    edited 2010-12-10 21:13
    An earth could be a possibility. I power my propeller boards from Wall-Wart plugpacks, and the transformer inside those is floating. So if I connect to a VGA display, the VGA display probably is the earth. I wonder what would happen though if you used one of the newer switching regulators - which I think do have ground connected to earth. Could you end up with hum loops for instance?

    For our OP, this might be tricky but it would be useful to compare earth on the VGA with earth on your demo board. But before you do that, what sort of power supply is running the demo board? There are some other unknowns here - eg if you were running off batteries the extra load of the vga pins could be enough to brown out the supply. The same could be true if running off a USB port.
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