32768 color dual Shifter ST mod - schematics lost?

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Badwolf
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by Badwolf »

sporniket wrote: Thu Jul 14, 2022 1:00 pm This time I ordered resistors with color rings instead of digits printed on it, so that I don't have to take care of bending the leads so that the digits are shown. But it's still inconvenient to check...
Mate, try SMD for one revision. I doubt you’ll go back to throughhole!

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sporniket
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by sporniket »

Badwolf wrote: Thu Jul 14, 2022 6:38 pm Mate, try SMD for one revision. I doubt you’ll go back to throughhole!
For other things...
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exxos
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by exxos »

sporniket wrote: Thu Jul 14, 2022 6:57 pm
Badwolf wrote: Thu Jul 14, 2022 6:38 pm Mate, try SMD for one revision. I doubt you’ll go back to throughhole!
For other things...
But then you have to buy twice as many SMT parts because of all the ones you drop on the floor and never find again! :lol:
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mrbombermillzy
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by mrbombermillzy »

exxos wrote: Thu Jul 14, 2022 7:07 pm
sporniket wrote: Thu Jul 14, 2022 6:57 pm
For other things...
But then you have to buy twice as many SMT parts because of all the ones you drop on the floor and never find again! :lol:
Reminds me of an 'Apple Engineer' we used to get come in our place to buy Dell laptops/tablets.

He told us he took a tablet to pieces to replace the screen. Used a heat gun to start to remove the screen and blew all the nearby screws off the table. :lol:
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mrbombermillzy
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by mrbombermillzy »

I've just been pointed to a thread on AtariAge by @exxos where a guy has just purchased an Atari STFM with the legendary JRI4096 colour board in it. :)

Whilst not the same as the Barry Orlando board, it may be worth a look:

https://forums.atariage.com/topic/34077 ... nt-5119872
Elliot
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by Elliot »

Am I right in saying that the STF pallet (RGB) is #000 to #777? From what I remember #888 on the STE is halfway between #000 and #111 and #999 is half way between #111 and #222.

What happens in an STF if you set a colour register to say #CCC, will you get a grey?
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sporniket
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by sporniket »

your right. On STe, to be backward compatible, the new least significant bit of color is put at position 3. Meaning if you want level 12 = $C = %1100, you have to convert it using the formula f(x)=(x >> 1)+ (x&1)<<3, ie (%110) + (0) = 6.

edit: thus, to get the STe level 1, you get (0) + (1<<3 = 8) = 8 ; level 3 -> (3 >> 1 = 1) + (1<<3 = 8) = 9 ; and so on.

On the stock STF, of course, the bit at position 3 is ignored, so each $C of #CCC will be seen as 4 and you get #444, mid grey
On a STe, writing #CCC, each C is interpreted as ((C & 7)<<1 = 4<<1=8) + ((C&8)>>3 = 8>>3 = 1) = 9, i.e you get #999, that will be slightly lighter than on the STF.
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Darklord
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by Darklord »

Just wanted to mention that I got lucky and picked up one of these
boards on Ebay about a week or so ago.

The JRI 4096 color board, that is...
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Darklord
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by Darklord »

Hmm, upon reflection - I wonder if this is something that tOri might be interested
in reverse-engineering? ;)
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