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Post by hydrophilic on Apr 14, 2016 8:39:01 GMT
You blew up your O'Scope? Wow! I feel for you!!
I published one or two RGB to SCART projects on my website, but they are not reliable... either it requires TV/monitor to have "manual" option to use RGB, or else you must build complex pair of cables (40-colum + 80+column -> SCART) with resistor network (that I can't test).
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Post by Pyrofer on Apr 14, 2016 12:43:19 GMT
On the up side it was my "old" scope which I kept at my parents. The newer LCD one still works (for now!). I got the TV to auto switch by linking 5v from my CGA=>RGB converter board to the fast blanking pin. People say you need 3v but I have done it a lot with 5v and no problem. My board already has plugs for both the 9pin from the VDC and the din plug from the VIC and has all the signals going into it so you can have a single scart with switch for 40/80 out. I also think I know why the VGA demo doesn't work, I have a PAL 128. The suggestion from the VGA demo text is that on a PAL 128 it outputs at 50hz and 60hz on an NTSC one. 60hz is WAY closer to VGA than 50hz is, so I will play with the registers to put the 128 in NTSC mode and try again. Sadly I need a scope to test the timings  |
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Post by tokra on Apr 14, 2016 15:47:18 GMT
Do you mean VDC VGA Mania? I wrote that demo and have a PAL C128 myself. The "VGA-style-mode"-register settings are close to 60 Hz/31.5 Khz, otherwise it should not matter what state the VDC registers are in before. If I remember correctly the demo starts in 40 column-mode to display the instructions and you should have the VGA-monitor connected after the RGBI->RGBA-converter with a standard VGA-cable.
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Post by Pyrofer on Apr 14, 2016 20:49:11 GMT
Oh my, Ok so you DO set it to 60hz in the demo?
Because NO vga monitor I have tried so far will show it.
Can I just check what you did for the cable... Did you connect vsync and hsync directly? Did you use a resistor? Did you invert either/or of the syncs?
I don't quite understand why I can't get a monitor to display as it sounds to me like it's close enough to real VGA frequencies to count. My old CRT monitor detected something and at least turned on but then had a blank screen.
I am using the same circuit I used to my SCART adapter which drops the RGB output levels to .7v. I have no idea why it's not working :Y
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Post by tokra on Apr 14, 2016 21:03:30 GMT
Yes, I set it to about 60 Hz. I use the RGBI->RGBA-converter from Richard42 whose design has been used as a basis for www.bit-c128.com as far as I know. I think HSYNC and VSYNC are combined to CSYNC by this. I think I tried it on two different TFTs with success back then. I found the original design docs by Richard42 on my hard-drive and have attached them to this post for future reference. |
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Post by Pyrofer on Apr 15, 2016 6:39:35 GMT
Ah, thanks for that. It seems to be inverting the sync on that schematic as well as combining it to combined sync. Which sync pin did you connect the composite sync to?
Did you leave the other one floating?
I shall have another go at getting it working this weekend.
Do you have notes on what registers you changed and what you changed them to for VGA mode?
I was thinking about trying it for a game (if I can make scrolling work!)
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Post by tokra on Apr 15, 2016 8:09:32 GMT
Sorry, I don't know the technical side of it. I just connected the VGA-connector to the DAC-board, you can see it working here: www.youtube.com/watch?v=zE-M2FnhWMASearching around the net, pin 13 of the VGA connector should be "HSYNC or CSYNC" so I suppose it goes there. You can find the register-settings in the BASIC-program itself at lines 1020,2020,3020 and from 4000 onwards for the text-mode with comments. |
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Post by Pyrofer on Apr 16, 2016 22:11:02 GMT
Nope. totally failed to get it working on any display  I am quite sad about this. I wonder what the problem is. |
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Post by tokra on Apr 17, 2016 13:43:50 GMT
Strange, just tried it with another TV/Monitor with VGA-In. Took 5-10 seconds to recognize the mode but then I got the text-display and the graphic-modes worked as well. Did you start the program and connect to VGA-In on your monitor?
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Post by Pyrofer on Apr 17, 2016 19:40:42 GMT
Hmm. I had it plugged in with the monitor on standby when I ran it. Maybe that confused the monitor. I will play some more.
I really need to get a scope connected and compare the sync pulses from a valid vga signal and from the vga demo.
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I am quite sad about this. I wonder what the problem is.