SVI-105M graphic tablet not showing same circuit logic as seen from wiki page

Door popolon_

Master (255)

afbeelding van popolon_

28-12-2021, 20:47

I obtained SVI-105M MSX graphic tablet that had cable cut away (only short torn wires left, no plug), so i had to open it to check how to wire it according to wiki page schematics link. But when i opened this SVI-105M, there is not same schematics at all inside when comparing to wiki page:
IMG_20211228_183537134.jpg
IMG_20211228_183513590.jpg

ADC chip is adc0833ccn, and there is fewer components in pcb. So I am not sure if this tablet is even working with msx standard or not? As the adc0833ccn datasheet does not show exact same behaviour as the uPD7001 (for example EOC vs SARS signals). And there was 8 signals (8 wires coming inside) connected, two wires are ground and +5v. One wire is connected to ground with jumper wire. There is alternative empty place jumper wire to connect this same signal to ground. But what signal is this then that can be connected to ground? Anyway there is only 5 signals for tablet specific signals, and in wiki page there are six signals SO/SI/EOC/_CS/SENSE/SCK. I figured out that
SO=adc0833ccn DO
SI=adc0833ccn DI
_CS=adc0833ccn _CS,
SCK=adc0833ccn CLK
but now the problem is that only one signal left, so SENSE or EOC ? That one signal that was connected to ground, could that be SENSE or EOC permanently and would that work? Or this tablet anyway needs specific tailor made software to work? I also opened then Pioneer PX-TB7 and verified that it really has that same logic chips as in wiki page.

I will next draw the schematics to kicad.

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Van mars2000you

Enlighted (6216)

afbeelding van mars2000you

28-12-2021, 21:27

Ac!ually, the link to a PDF file concerns the SVI-105 without M, it is for SVI-318/328 computers.

Van popolon_

Master (255)

afbeelding van popolon_

28-12-2021, 22:13

yes, i noticed that it was for svi-105, but same components (for example ICs and transistor amounts) seems to be also in pioneer MSX tablet. And connections towards joystick port pins are same logic (of cource different pinouts in msx vs SVI3x8).

Anyway the schematics for this SVI-105M MSX tablet is:
svi105m_schematics.png

Van sdsnatcher73

Prophet (3203)

afbeelding van sdsnatcher73

29-12-2021, 05:32

It seeems then you got it working again, right?

Van popolon_

Master (255)

afbeelding van popolon_

29-12-2021, 08:45

No, it is not working yet, i just draw the schematics, and the eoc/sense signals are not connected now as there is only one wire for one of those. And the left over signal would be going straight to ground.

Van sdsnatcher73

Prophet (3203)

afbeelding van sdsnatcher73

29-12-2021, 09:25

Well EOC is the output of the ADC so it definitely should not go to ground in my opinion.

Van popolon_

Master (255)

afbeelding van popolon_

29-12-2021, 10:13

EOC was output from 7001 adc, but in adc0833 there is only SARS signal. Anyway the joystick port side pin is connected to ground, it does not short any adc output to ground. So SENSE signal would be always connected to ground but only software from spectravideo would work? Alternative would be to have EOC joystick pin always on ground and SENSE signal coming from SARS. But can i connect pin 1 or 2 to ground, or would it fry something?

Does anybody have the software that was in the cassette?

Van popolon_

Master (255)

afbeelding van popolon_

31-12-2021, 12:36

I tried the tablet on Hitachi H3(internal touch pad disabled, external tablet in joystick port 2) but it does not work. SENSE signal was connected to ground and EOC to SARS. Anyway Pioneer PX-TB7 tablet works fine in same computer.

Van popolon_

Master (255)

afbeelding van popolon_

04-05-2022, 19:50

both svi and msx versions looks the same from outside.
IMG_20220504_204143178.jpg

IMG_20220504_204645271.jpg

Van popolon_

Master (255)

afbeelding van popolon_

04-05-2022, 20:07

And i got the svi3x2 software cassette for svi-105 tablet, and it is working. But still missing that msx software cassette for this svi-105m msx tablet.