My summer project: A colour Stacy

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derkom
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My summer project: A colour Stacy

Post by derkom » Wed Jul 01, 2020 10:59 am

Heh, who would have guessed that @Atarian Computing and I were coincidentally working on similar projects? :lol:

I was planning to keep this under wraps until I was done, but I figure now I might as well share, because perhaps we both have some ideas for each other.

I acquired a broken French Stacy early this year and fixed it (bad MMU and bad power switch), but the backlight was in terrible condition, so I decided to explore replacing the display with something modern, and preferably supporting all three graphics modes. People who have tried this before have found that there really isn't a good drop-in replacement for the old screen, but it occurred to me that there's really no reason I can't install a screen that's actually a bit too big, and just ensure that I can scale its input to fit the bezel opening.

I opened up the Stacy and measured the minimum size that would fill the bezel and also the maximum size that would fit between the screw anchors, and plugged that range into an LCD panel search engine and found that the HannStar HSD121PHW1-A03 was a good candidate, and available on AliExpress for around 40€, and I paired it up with this LVDS controller board.

After waiting ages for both parts to arrive from China, I 3D printed some brackets to hold the panel into the Stacy lid, and here's the result (note that the protective plastic is still on the screen here, as I won't remove that until everything is done):

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I hooked up the controller board and plugged the monitor output from the Stacy into an OSSC, and voila...

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(TOS 2.06 provided by the excellent Cloudy flash TOS board.)

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(Still need to work on the OSSC timings to make that look a little better, but I won't do that until the end.)

The LCD controller board has a little daughterboard with buttons to adjust its settings, so I 3D printed a replacement RAM access door, with buttons blatantly pilfered from this great design:

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I have replaced the internal PSU (no longer needed since the exotic backlight in the original screen is gone) with a picoPSU, and I've 3D printed a bracket to allow the OSSC board to sit where the old SCSI controller used to live. Today I am in the process of tapping the internal video, which I plan to feed through an internally mounted exxos V4 colour/mono switcher, and also on the roadmap is a Thunder for USB/IDE, and a Storm ST for ALT-RAM. And if I can make it work, possibly a TF536 eventually. I just sent off a little PCB design to Aisler for a CPU relocator that should make it fit, but I admit that I am not anticipating full success on this part. :D

I don't know how well this stuff will all eventually work together, but progress so far has been pretty promising. Time will tell!

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Re: My summer project: A colour Stacy

Post by Cyprian » Wed Jul 01, 2020 11:12 am

well done,
as far as I remember Stacy had only monochrome mode. Do you have all video modes?
what about borders? would be possible to remove them?
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Re: My summer project: A colour Stacy

Post by derkom » Wed Jul 01, 2020 11:21 am

Cyprian wrote:
Wed Jul 01, 2020 11:12 am
well done,
as far as I remember Stacy had only monochrome mode. Do you have all video modes?
what about borders? would be possible to remove them?
The Stacy can do all three ST video modes, but only hires mono on the internal display. But as far as the Stacy is concerned, this is an external display, and the Stacy will output either colour or mono, depending on the mono detect line, which can be toggled via the exxos VGA adapter.

As for the borders, this solution is never going to have the pure edge-to-edge pixel perfection of the original display. I will eventually adjust the borders as best I can, using the OSSC timing controls. (Atarian Computing's similar build might achieve border-free, though, since he has a panel with an exact multiple of the ST pixel count, and also he's got the whole screen available for use, where mine is sacrificing some pixels on all four sides.)

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Re: My summer project: A colour Stacy

Post by Icky » Wed Jul 01, 2020 11:27 am

Great work. Very nice replacement and the buttons option by replacing the ram door is genius to not cut holes or destroy the case etc.

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Re: My summer project: A colour Stacy

Post by derkom » Wed Jul 01, 2020 11:36 am

Icky wrote:
Wed Jul 01, 2020 11:27 am
Great work. Very nice replacement and the buttons option by replacing the ram door is genius to not cut holes or destroy the case etc.
One of my goals here is not to modify permanently. The screen I used is so close to the horizontal limit that I actually did have to dremel off one of the little support fins on each of the four screw achors it abuts, but that's a very minor alternation, and doesn't show since it's internal.

Also I socketed the CPU to allow for the upgrades to go in, but we can allow that kind of modification. :lol:

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Re: My summer project: A colour Stacy

Post by Steve » Wed Jul 01, 2020 11:38 am

Hey derkom why not try a retrotink scart scaler? Might be more suitable, smaller and less hassle than an ossc. You also won't need the VGA adapter then.
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Re: My summer project: A colour Stacy

Post by derkom » Wed Jul 01, 2020 11:42 am

Steve wrote:
Wed Jul 01, 2020 11:38 am
Hey derkom why not try a retrotink scart scaler? Might be more suitable, smaller and less hassle than an ossc. You also won't need the VGA adapter then.
Well, I guess because I don't have one. :lol:

How would that eliminate the need for the VGA adapter, though? The main purpose of the VGA adapter in this build is to allow for colour/mono switching. If I wanted only colour or only mono, I could just feed directly from the Stacy to the OSSC. I think the Retrotink would be no different in this regard?

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Re: My summer project: A colour Stacy

Post by Atarian Computing » Wed Jul 01, 2020 11:54 am

derkom wrote:
Wed Jul 01, 2020 10:59 am
Heh, who would have guessed that @Atarian Computing and I were coincidentally working on similar projects? :lol:
Holy moly! Well done mate! Very inspiring, and you've given me something to think about. I love the 3D-printed parts!

I also just realized I never answered or even noticed your last post in my thread. Sorry about that. As for my projects, obviously you have a Cloudy so my project that was on hold is now obsolete :)

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Re: My summer project: A colour Stacy

Post by thorsten.otto » Wed Jul 01, 2020 11:58 am

derkom wrote:
Wed Jul 01, 2020 11:21 am
The Stacy can do all three ST video modes, but only hires mono on the internal display.
The original TOS for Stacy is a bit different, so maybe this only works because you replaced it ;)

However, TOS 2.06 is missing some other support specific to the Stacy (the bios WakeUp() call for example).

Anyway, congrats to get that working ;)

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Re: My summer project: A colour Stacy

Post by derkom » Wed Jul 01, 2020 12:02 pm

thorsten.otto wrote:
Wed Jul 01, 2020 11:58 am
derkom wrote:
Wed Jul 01, 2020 11:21 am
The Stacy can do all three ST video modes, but only hires mono on the internal display.
The original TOS for Stacy is a bit different, so maybe this only works because you replaced it ;)
I'm not sure what you are saying here. The original Stacy TOS 1.04 has no problem displaying colour modes on a colour display plugged into the external monitor port.

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