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Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9066

Posted: 07:51pm 11 Sep 2014

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Hi all.

This question is similar to the one I posted a while back about forcing the VT100 into VGA mode from power-up, even if no monitor connected.

On the MaxiMite series, pin 9 of the VGA socket comes back to C14 on the PIC32 chip, and is labelled SELECT COMPOSITE.

Looking at the pinout for the VGA connector, it would seem that pin9 here is 5v in most monitors, so I would guess that the MaxiMite looks at C14 and if it is high, it assumes VGA monitor, and if it is low, it assumes no VGA monitor, so sets itself up for composite.

Yes?
No?

With the above in mind, and assuming I have that right, then if I pull C14 high with a 4k7 or so, this should permanently force the MaxiMite into VGA-only mode.

Yes?
No?

It would appear that C14 is 5v tolerant, so I could pull it to either 5v or the 3v3 system supply.

Yes?
No?

Thanks for any replies.

Smoke makes things work. When the smoke gets out, it stops!

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3165

Posted: 10:21pm 11 Sep 2014

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Grogster said On the MaxiMite series, pin 9 of the VGA socket comes back to C14 on the PIC32 chip, and is labelled SELECT COMPOSITE.

Looking at the pinout for the VGA connector, it would seem that pin9 here is 5v in most monitors, so I would guess that the MaxiMite looks at C14 and if it is high, it assumes VGA monitor, and if it is low, it assumes no VGA monitor, so sets itself up for composite.

The VGA convention is that pin 9 should be unconnected in the monitor although since then I have found that a lot of monitors (particularly H/P) use that pin for other purposes.

When pin 9 is unconnected a pullup inside the PIC32 will pull it +ive and VGA is selected. When that pin is grounded composite is selected. This is disabled if you use the command CONFIG COMPOSITE DISABLED (which is the default for a newly flashed MMBasic).

So, for permanent VGA you can:
- do nothing (composite and pin 9 are disabled by default)
- or use the command CONFIG COMPOSITE DISABLED
- or cut the trace to pin 9 on the VGA connector

Geoff

Geoff Graham - http://geoffg.net

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9066

Posted: 02:17pm 12 Sep 2014

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Thank you very much - exactly what I needed to know.

Smoke makes things work. When the smoke gets out, it stops!

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