29 Jan
2004
29 Jan
'04
4:36 p.m.
I would like to connect the RGB TTL output of a BBC micro to
a VGA monitor, does anybody have any pointers - suggestions?
Thanks
**vp
31 Jan
31 Jan
3:09 a.m.
Vassilis Prevelakis wrote:
I would like to connect the RGB TTL output of a BBC
micro to
a VGA monitor, does anybody have any pointers - suggestions?
Thanks
**vp
It's not worth your while trying, it would be cheaper to buy a bbc
monitor from ebay. Or a tv-in for your pc and connect it to the bbc's
uhf out.
Dan
11:56 a.m.
I would like to connect the RGB TTL output of a BBC micro to
a VGA monitor, does anybody have any pointers - suggestions?
It's very difficult...
The trivial problem is that he RGB socket on a Beeb is TTL level digital,
the VGA input is analogue. Trivial, because there's only 1 bit per colour
on the Beeb anyway, so a resistor network will convert the voltage levels.
The difficult problem is that the scan rates are totally different (VGA
is 31kHz horizontal, the Beeb is 15.625kHz). If you have a multisync
monitor that will go down to 15kHz (some of the old ones will), then
there's no problem, otherwise you've got a lot of work either modifying
the monitor or making a standards converter.
Probably the easiest solution if you're not a video expert is to use a PC
with a TV input card. You could at least feed the Beeb's composite output
into such a card (do any such cards exist with RGB inputs?)
-tony
10:01 p.m.
Tony Duell wrote:
wasn't there a hack on the mainboard to convert the composite to colour
Dan
I would like to
connect the RGB TTL output of a BBC micro to
a VGA monitor, does anybody have any pointers - suggestions?
It's very difficult...
The trivial problem is that he RGB socket on a Beeb is TTL level digital,
the VGA input is analogue. Trivial, because there's only 1 bit per colour
on the Beeb anyway, so a resistor network will convert the voltage levels.
The difficult problem is that the scan rates are totally different (VGA
is 31kHz horizontal, the Beeb is 15.625kHz). If you have a multisync
monitor that will go down to 15kHz (some of the old ones will), then
there's no problem, otherwise you've got a lot of work either modifying
the monitor or making a standards converter.
Probably the easiest solution if you're not a video expert is to use a PC
with a TV input card. You could at least feed the Beeb's composite output
into such a card (do any such cards exist with RGB inputs?)
-tony
11:15 p.m.
At 12:01 PM 2/1/04 +0000, you wrote:
Tony Duell wrote:
>>I would like to connect the RGB TTL output of a BBC micro to
>>a VGA monitor, does anybody have any pointers - suggestions?
>>
>>
>
>It's very difficult...
>
>The trivial problem is that he RGB socket on a Beeb is TTL level digital,
>the VGA input is analogue. Trivial, because there's only 1 bit per colour
>on the Beeb anyway, so a resistor network will convert the voltage levels.
>
>The difficult problem is that the scan rates are totally different (VGA
>is 31kHz horizontal, the Beeb is 15.625kHz). If you have a multisync
>monitor that will go down to 15kHz (some of the old ones will), then
>there's no problem, otherwise you've got a lot of work either modifying
>the monitor or making a standards converter.
>
>Probably the easiest solution if you're not a video expert is to use a PC
>with a TV input card. You could at least feed the Beeb's composite output
>into such a card (do any such cards exist with RGB inputs?)
The alternative is to use a scandoubler such as a Micomsoft XRGB 1, 2, or
2+. These upscan composite video, S-video (NTSC only) and analog RGB to
VGA. They aren't cheap, (I paid US$200 for my XRGB2) but the quality is
far better than any of the cheap video to VGA boxes I've tried. I use mine
with various game consoles and home computers.
As a side note, any suggestions on how to convert CGA to analog RGB so I
can run my Tandy 1000 through it?
1 Feb
1 Feb
3:37 a.m.
As a side note, any suggestions on how to convert CGA
to analog RGB so I
can run my Tandy 1000 through it?
Well, what you need to do is use some buffers and resistors to combine
the RGBI digital signals into 3 analogue signals (look at the schematics
of a CGA monitor for detials). If you don't mind just having 8 colours,
you can ignore the I signal, and just use potential dividers to reduce
the TTL signals to the 1V analogue levels (a quick-n-dirty solution if
the analogue inputs are terminated with 75 ohms, as they should be, is
just to put a 300 ohm resistor in series with each of the 3 digital signals).
Then you have to sort out the syncs. Typically you need to Xor the 2
syncs on the CGA connector to get a composite sync. Then maybe invert
that. Maybe bring that down to 1V levels with a 300 ohm series resistor.
-tony
3:33 a.m.
Probably the
easiest solution if you're not a video expert is to use a PC
with a TV input card. You could at least feed the Beeb's composite output
into such a card (do any such cards exist with RGB inputs?)
-tony
wasn't there a hack on the mainboard to convert the composite to colour
7411
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7413
days old
6 comments
4 participants
participants (4)
-
ard＠p850ug1.demon.co.uk -
dan_williams＠ntlworld.com -
dr.ido＠bigpond.net.au -
vp＠mcs.drexel.edu