[EN] sAIOnara-XE(XL) - ready to use with video mod for VBXE - t.b.c.

[pancio]

I would like to present another interesting very simple interface, which we install instead of a TV modulator. It allows the processing of RGB signals from VBXE into very good quality SVIDEO and CVBS (Composite) signals. The following system is based on the CXA1645M and is an extension of the system described in the article:

[EN] SavoNARA: VBXE2VGA/SVIDEO - CXA1645

Main features:

• generating very good quality video signal in SVIDEO mode (LUMA + CHROMA),

• generating very good quality CVBS signal (COMPOSITE),

• buffering and improving RGB signal and generating separate H and V sync signals,

• correcting discoloration and sharpening the image for CVBS mode,

• outputting RGBs and stereo audio signals outside the computer via miniDIN-9 socket, without destroying the casing,

• can be used directly with a SEGA cable (miniDIN-9 to SCART) or with a miniDIN-9 to VGA cable (DB9 or DB15) - see description below,

• supplies power (+5V) to the optional VGA2HDMI converter via miniDIN-9 socket,

• outputting SVIDEO/CVBS signals with VBXE effects via a standard DIN-5 monitor socket,

• convenient and easy to install and stable interface (no gluing with adhesive tape like 'savo family'),

• the interface is available in two versions, separately for XE and XL computers - this is due to the space available after removing the TV modulator.

sAIOnara-XE is another project created as part of the activities of PTODT (Polish Society for the Protection of Technical Heritage), established to protect technical heritage, in particular in the field of computer science and computers. I encourage you to visit the association's website and support our activities:

Polskie Towarzystwo Ochrony Dziedzictwa Technicznego/


License Information
The project was made as Free Hardware under the Creative Commons BY-NC-SA 4.0 license. This means that you can make it yourself, for private use. Commercial use is possible after obtaining the authors' consent.

Warning!
Everything you do - you do at your own risk. In this article I describe activities that, if you lack experience in electronics, can damage your device...


Schematic
The device structure is shown in the diagram below:

sAIOnara-schematic.png (193.29 KiB) Viewed 367 times

The main component used by the interface is the Sony CXA1645M, which contains an RGB decoder for CVBS and SVIDEO signals. Additionally, the CXA1645M shapes the RGB signal (buffers and improves quality) and does not require an additional amplifier.

sAIOnara can be equipped with an additional LM1881 chip, which allows to separate vertical and horizontal synchronization required by some monitors in RGBs mode, but it is not necessary (the OPTION block is marked on the diagram).

For correct operation, the CXA1645 requires a synchronization signal - this signal is taken from pin 15 of the 4050 integrated circuit in Atari - marked with the symbol S on the PCB.

It is also worth adding that the presented solution allows you to work in both PAL and NTSC mode - the mode selection is just one resistor: R8.

Code: Select all

16k for PAL
20k for NTSC 

For users who wish to use CVBS, the PCB is equipped with an additional trimmer (C12) that allows for color and sharpness correction.

I used a miniDIN-9 socket, which allows the use of a standard SEGA miniDIN-9 to SCART cable and direct connection to the TV or use this output to transmit the appropriate signals (RGBs) to the HDMI grabber. I don't have to mention that using the HDMI grabber allows you to play with Atari using practically any monitor or modern TV


PCB design, assembly and installation
Since Atari TV modulators come in at least two versions (referring to dimensions and the way they connect to the computer), I had to design two variants of the sAIOnara. It is also possible that the dimensions of the PCB for the 600XL computer will need to be changed, but I will not be able to confirm this until I receive the boards for the sAIOnara-XL.

modulators_and_sAIOnara.jpeg (866.08 KiB) Viewed 327 times

sAIOnara-XE:

sAIOnara-XEv2.1-front.png (313.53 KiB) Viewed 330 times

sAIOnara-XEv2.1-back.png (165.82 KiB) Viewed 330 times

sAIOnara-XEv2.1-board.jpeg (826.55 KiB) Viewed 317 times

To set the sAIOnara at the right height, you need to adjust the length of the pins connecting the Atari to the sAIOnara so that both the Atari and sAIOnara boards are parallel to each other. I used a regular pin-socket for this, and longer pins extracted from a two-row pin-header:

pinheader_and_pinsocket.png (2.47 MiB) Viewed 328 times

pinheader_and_pinsocket2.png (1.68 MiB) Viewed 328 times

pinheader_extraction.png (2.95 MiB) Viewed 328 times

install_pins_into_sAIOnara.png (4.38 MiB) Viewed 328 times

sAIOnara-XL:

sAIOnara-XLv2.1-front.png (262.9 KiB) Viewed 330 times

sAIOnara-XLv2.1-back.png (159.74 KiB) Viewed 330 times

Connectors:
J1 - Audio input connector - should be connected to your Pokey Stereo device (e.g. PTODT Stereo, Simple Stereo,PokeyMax),
J2 - Power distribution - if closed, 5V will be available on pin 3 of J3 (miniDIN-9). It's necessary for external RGB2HDMI grabber and for automatically switch your TV to RGB mode,
J3 - miniDIN-9 socket witch all video/audio/sync signals,
J4 - Audio/Video output - this connector has two functions - is the source of SVIDEO/CVBS for DIN-5 socket (original Atari's A/V output) or signal's source for SVIDEO2HDMI grabber.
J5 - RGB/sync input - you should connect R, G, B signals from VBXE and SYNC/PAL from Atari to this connector.

There is one more connector which is not mentioned above placed on the bottom of PCB - it's 5 pins header which you should use as sAIOnara position lock relative to Atari board. It might be use as 5V input as well (pin 4).

PCB assembly
The board is prepared for mounting SMD 0805 passive components, but several larger capacitors are mounted on 1206 pads. Personally, instead of 0805-sized components, I install 0603-sized components - it is definitely easier to solder them when we have little space around them.

A short description of PCB assembly. We start the assembly by soldering the LM1881 circuit and passive elements on the LM side. Then we mount the CXA1645M chip and then the remaining passive SMD elements. In the next step, I suggest soldering the THT electrolytic capacitors and the trimmer. Finally, we mount the pin strips and the miniDIN-9 socket.


t.b.c.