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Forum Index : Microcontroller and PC projects : Forcing the VT100 terminal to VGA...
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Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9066 |
Hi folks. Geoff's VT100 terminal - in the July 2014 issue of SC, this unit is described, and on page 62, the text mentions that updn boot-up, the firmware looks at pin 12 to see if there is a VGA monitor connected, and if not, then it defaults to composite video. I need it the other way around - VGA by default, even if no monitor actually connected at boot-up time. To force this to happen, I have wired a 1k8 resistor across pin12 and ground, and this does seem to be working, but is this an acceptable way to do it, or should I be doing this a different way? Smoke makes things work. When the smoke gets out, it stops! |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 5913 |
That is more or less what a monitor does so it should be safe to do. Jim VK7JH MMedit MMBasic Help |
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Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9066 |
Cool, thanks. I was just a little un-easy about that approach, in case I would be upsetting the PIC32 or the monitor. Smoke makes things work. When the smoke gets out, it stops! |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 5913 |
I misread your question and was wrong anyway. The maximite monitors pin 9 of the VGA connector. Relying on pin 9 of the VGA connector did cause problems which might explain the change. A better answer: The input impedance of the 3 colour lines on a VGA monitor is 75 ohms each and there is a 220 ohm resistor on the VGA output of the CPU. Having a 1.8k in parallel with the existing (220+75) should not put too much extra load on the CPU pin. Jim VK7JH MMedit MMBasic Help |
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Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9066 |
Acknowledged - thanks. Smoke makes things work. When the smoke gets out, it stops! |
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