Author Topic: A potential PCW project  (Read 562 times)

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Online tjohnson

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A potential PCW project
« on: 22:59, 30 January 19 »
I was sitting at home yesterday, after reading the thread about trying to get a Superbrain working with an Amstrad monitor and had a thought an empty PCW case I have in the garage.  I used the board to upgrade my 464+ so have the case and monitor left over.  I suddenly thought it would be marginally interesting to hook the monitor up to a Raspberry Pi and run Joyce and an Caprice on it.  I assume I could hook the composite output up to the monitor input or is it more complex than that?

Offline JonB

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Re: A potential PCW project
« Reply #1 on: 20:27, 31 January 19 »
More complex. The Pi has a composite video output but the PCW needs separate sync / luminance (video) signals.

You need a sync splitter. There are some circuits for this but I couldn't find one that takes composite and gives CSYNC and VIDEO output, yet.

Online tjohnson

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Re: A potential PCW project
« Reply #2 on: 09:50, 01 February 19 »
What if I used an hdmi to vga the recombined the seperate sync signals then only used the rGb ?

Online tjohnson

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Re: A potential PCW project
« Reply #3 on: 09:51, 01 February 19 »
What if I used an hdmi to vga then recombined the seperate sync signals then only used the rGb ?

Offline JonB

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Re: A potential PCW project
« Reply #4 on: 10:37, 01 February 19 »
I think the VGA sync frequencies are too high for the Amstrad monitor. Much easier to split the composite sync from the Pi. Cheaper, too.

Online tjohnson

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Re: A potential PCW project
« Reply #5 on: 16:52, 01 February 19 »
I think the VGA sync frequencies are too high for the Amstrad monitor. Much easier to split the composite sync from the Pi. Cheaper, too.
Yeah good point VGA is 31khz while composite is 15khz.  Could I use an LM1881 to seperate out the sync signal but presume then I still have the issue of the sync on the video?  I had previously used HDMI to VGA but force 15khz through the config.ini but most HDMI>VGA struggle with that.
« Last Edit: 16:54, 01 February 19 by tjohnson »

Online tjohnson

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Re: A potential PCW project
« Reply #6 on: 16:53, 01 February 19 »
dups

Offline Token

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Re: A potential PCW project
« Reply #7 on: 04:09, 02 February 19 »
You can get 15KHz with a PI and a cheap HDMI to VGA converter + the 240p config file. I added a DIN6 for my CTM644 and GT65. There is also the GERT VGA 666 module (cheap as well) but I prefer the first solution.

https://www.youtube.com/watch?v=z-9LAmeZuxI

Online tjohnson

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Re: A potential PCW project
« Reply #8 on: 12:11, 02 February 19 »
You can get 15KHz with a PI and a cheap HDMI to VGA converter + the 240p config file. I added a DIN6 for my CTM644 and GT65. There is also the GERT VGA 666 module (cheap as well) but I prefer the first solution.


Thanks I've got a pi3 setup at home in a cab I made myself but have found the hdmi adapters for vga often struggle with 15khz, I have one that works but sometimes the image goes off and another that doesn't work at all but we'll worth a try so thanks for the suggestion I'll give that a try.  Also might look at the gert666 I had intended to use an original pi model so this should work.

Offline Token

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Re: A potential PCW project
« Reply #9 on: 16:08, 02 February 19 »
I've seen that too late in the night that you tested it yet  :picard:
I have the GERT 666 as well, it's nice even if I have read that it could reduce the color palette (6-bits per colour channel) I haven't see it (and I have use it as video player too)
The good point is it doesn't get hot like the HDMI-VGA converter. If I didn't have problem with it I'm thinking to use a heatsink like I did on a wifi dongle.

Online tjohnson

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Re: A potential PCW project
« Reply #10 on: 11:29, 03 February 19 »
I've seen that too late in the night that you tested it yet  :picard:
I have the GERT 666 as well, it's nice even if I have read that it could reduce the color palette (6-bits per colour channel) I haven't see it (and I have use it as video player too)
The good point is it doesn't get hot like the HDMI-VGA converter. If I didn't have problem with it I'm thinking to use a heatsink like I did on a wifi dongle.


Thanks token I think I'll try with one of my hdmi to vga adapters first and see how that goes, I guess I'll need to recombined the sync signals?  I have been checking caprice32 for raspberry pi and it supports a green screen option  I haven't checked or Joyce yet 

Offline Token

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Re: A potential PCW project
« Reply #11 on: 16:43, 03 February 19 »
Tjohnson, I'm drawing it, will post soon. CTM644 only, I made a very short cable to convert to mono. (it's just RGB line connected to LUM center pin with a resistor)
PS: I made this cable long time ago. (maybe the resistors aren't 75 ohm) With PCW to GT65 monitor I will quote what I did before:I added a 100 Ohm resistor on the Vsync (and also on the Lum/RGB, but I think it's not necessary) So the picture is not cropped anymore on top and bottom.
« Last Edit: 17:48, 03 February 19 by Token »

Offline Token

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Re: A potential PCW project - VGA 2 CPC DIN 6 cable
« Reply #12 on: 17:31, 03 February 19 »

Online tjohnson

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Re: A potential PCW project
« Reply #13 on: 01:29, 05 February 19 »
Thanks Token will have a go
Well I've managed to compile Joyce for my Raspberry Pi 1 and it runs really well, full speed as far as I can tell, been playing Tetris on a PCW emulated on a raspberry pi, not see if I can get it to output on a real PCW monitor.

Online tjohnson

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Re: A potential PCW project
« Reply #14 on: 14:52, 09 February 19 »
More complex. The Pi has a composite video output but the PCW needs separate sync / luminance (video) signals.

You need a sync splitter. There are some circuits for this but I couldn't find one that takes composite and gives CSYNC and VIDEO output, yet.


Right I've had a little play around today and no its not quite straight forward, the monitor has an internal 74hc00 ic which I presume buffers the the PCW hence why people use this when connecting to a monitor but if I try and feed it with a signal out of VGA then I think the signal levels are too low.  Need to have another think :)