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Post by Pyrofer on Apr 25, 2016 16:13:28 GMT
That chip is interesting. However, what do you intend to actually use to render the image?
Interestingly that chip looks like it might work in conjunction with the VDC. It seems it might be possible to use that to manipulate the VRAM and then have the VDC render it to screen.
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Post by Pyrofer on Apr 25, 2016 15:19:06 GMT
It's super easy to make a VDC based plugin card for the C64/128. In fact I have now seen a photo of a prototype of the C64 card so I know it's as simple as I thought. You just need the VDC, a clock source, DRAM and a couple logic chips, done.
Also, I am toying with the idea of making an FPGA VDC replacement that outputs at VGA frequency. I have a dev board on order and will start playing with getting it to work the same way the VDC does. The hope is I could make a drop in replacement like the SwinSID that turns it into a VGA frequency output (maybe have a connector on the plugin board to avoid modding the C128 mobo to allow the analogue signals out).
If I did this the chip could be used on your plugin card to avoid requiring lots of 30 year old VDC chips which are hard to get now. VGA would also be more useful as an output.
Any interest in such a thing?
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Post by Pyrofer on Apr 19, 2016 10:33:06 GMT
Tokra has proven that we are indeed all idiots in some way. His smooth scrolling test demo indeed works flawlessly in VICE (Not tried on real hardware yet).
I am going to have to go through his code and mine line by line working out where the differences come. I really wan't to find the reason that mine flickers as honestly, I can't see it.
I assume that this scrolling text demo flickers for the exact same reason as my vertical scroller does so when we lock down the reason everybody who wants to play with the VDC can benefit from it.
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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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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 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 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 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 Pyrofer on Apr 12, 2016 19:52:01 GMT
So the smooth scrolling works, but is buggy. However it sort of scrolls. I started making some nicer graphics and am now wondering about using the double wide mode. Not sure if that works in bitmap mode or only character mode, need to test. Not really making use of the higher resolution with the VDC here
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Post by Pyrofer on Apr 12, 2016 7:08:28 GMT
BEQ seems to just lock it up. Which is odd. It freezes and doesn't scroll. I will play with that. I check the status reg in a lot of places but mostly you don't actually need to. You can fill the registers without much trouble, it's only when you start writing byte after byte of data to the thing that it needs status checking. I tested that quite heavily in Boulder Dash when speeding it up. Default character height is set, so 8 pixels. The smooth scroll register seems to know about that, if you try moving extra pixels it doesn't work and just wraps back to the first. Yeah, I did basic scrolling up the screen first (which doesn't require double buffering, down does). I did it pixel smooth at first without the hardware register and it worked fine. Then I added the hardware register for pixel offset and scrolled a whole 8 pixels at a time and it jumped just like in this video. I DON'T trust VICE. I found that out with Boulder Dash. I use a real flat 64k upgraded 128 to test on (which caused ALL sorts of problems before I found out that I had to set the bit to tell it there was 64k of vram!) Does pretty much the same on real hardware as emulator for this bug. I am pretty sure VICE is representing the problem correctly and I just need to work out how to get around it. It looks to be the same issue the other guy doing a simple text scroller came accross, but in the other axis for me. (btw, for that many pixels I could smooth scroll the shit out of that text without jitter).
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