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Re: dual screen

Tue Mar 13, 2012 11:16 am

Hi ,

is it possible to set up the system for dual screen boot from the two outputs (HDMI/RCA).

Can this be done from Debian or anyother operating system or does the chip prohibit this internally?


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Re: dual screen

Tue Mar 13, 2012 11:29 am

I'm sure it is mentioned in the FAQ, but no HDMI or RCA not both
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Phil Spiegel
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Re: dual screen

Tue Mar 13, 2012 11:34 am

No Dual Screen: the HDMI has 'priority' because it can check for the presence of the monitor (and it capabilities?) ..whereas a composite output is unidirectional, unintelligent, only:

If using Composite and not HDMI therefore:

In first use you may have to rely on most TV/monitor's abiliites to work on 50/60Hz, as it appears the default config file will be set for 'NorthAmerica' NTSC 60Hz(approx) 3.38MHz colour subcarrier.

Other  options being JapaneseNTSC, PAL(50Hz-625 4.43MHz) and Brazillian NTSC

Perhaps a serial output (via USB converter) could be used for a 2nd terminal type display.

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Re: dual screen

Tue Mar 13, 2012 12:08 pm

Phil Spiegel said:

Perhaps a serial output (via USB converter) could be used for a 2nd terminal type display.

I've got a nice Dec VT220 terminal I could use..... Humm.....

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Re: dual screen

Tue Mar 13, 2012 10:43 pm

X Windows is a network protocol. You can run an application on one host and have the display appear on another host. In the dark ages, or the mid-1990's, whichever is most recent, I fired up X windows on a pair of computers. Then I fired up a program which ran X Windows on top of that. The upper layer X Windows treated the native copies of X Windows as if they were (slow) monitors. This produced the magic effect, that windows could be slid off of the side of one screen, onto the other screen.

It was like having a modern multi-screen system, except that the only connection between the two computers was the blazingly slow 10Mbit ethernet. It worked fine given the constraints of the systems. I had two Sun 3/50 computers. They were upgraded to a massive 12 Mbytes of RAM each. Normally, a Sun 3/50 could only drive one monitor. These were monochrome, not even grayscale. The software didn't support things like rendering contexts, Open GL, or any other X extensions, but it didn't matter, as neither did the hardware.

My google skills are failing me. I can't recall what it was called. Xpra,, looks like it lets you move a window from one host to another host, but it doesn't turn the two hosts into a single large virtual display sharing a single keyboard. With Xpra, you have a keyboard and mouse per display. Xpra, and two Raspberry Pis would be an upgrade compared to a Raspberry Pi and a VT220.

Do any old timers remember the software? Is there a modern equivalent that will work with Open GL applications?

To review: the software let me run two (or more) computers, with one mouse, one keyboard. It would forward my keystrokes and mouse events over the network, to the other computer, when I slid the mouse off one screen, onto the other. Windows could be half on one monitor, half on the other. If the CPUs weren't too busy, it wasn't even very painful.  (Each Sun 3/50 68020 was rated at 1.5 MIPS. A Raspberry Pi should be about 200 times faster.)

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Re: dual screen

Tue Mar 13, 2012 10:53 pm

This looks workable:

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Re: dual screen

Tue Mar 13, 2012 11:06 pm

andytuk said:

Phil Spiegel said:

Perhaps a serial output (via USB converter) could be used for a 2nd terminal type display.

I've got a nice Dec VT220 terminal I could use….. Humm…..

Oooh nice!  I preferred the VT420 TBH

I have (bizarrely) a pair of VT220 compatible Data General Green Screens in the attic, one of which I WILL extract and hook up to my raspi IF:

a) A simple Serial Port solution/config can be engineered using USB

b) I can wire up an old 25pin to 9pin RS232 convertor cable

EDIT: I just noticed my Fedora Dell D610 has a 9 pin RS232 port on the back - woo hoo
Steve N – binatone mk4->intellivision->zx81->spectrum->cbm64->cpc6128->520stfm->pc->raspi ?

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Re: dual screen

Fri Sep 14, 2012 7:56 pm

I remember good old X Windows. No clue what the current LINUX version is (MickeySoft has Mouse Without Borders).

Theoretically speaking, any USB display adapter that is supported by LINUX (preferrablly Debian) would work as a secondary screen.

Mind you, I'm speaking hypothetical, and can't it would really work. It would be fun to find out, though. I'm trying to design a system that pipes video two different types of displays. (if you're interested, working on a small arm-mounted touchscreen and a t-foled helmet overlay for a motorcycle helmet. GPS, bluetooth, and Telemetry data)
I'm only wearing black until they find something darker.

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