7 segment display decoder with HEX output

Posted on October 8, 2020 by Andrew

In seeking to improve my ISA POST card design, I became frustrated at the general lack of modern seven segment display decoders that could decode and display a hexadecimal output. Rather than buy an older second-hand decoder IC, I fell down the rabbit hole of programming a PLD device to accomplish the task.

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New Github

Posted on May 25, 2020 by Andrew

I’ve had a recent reader comment asking for me to share the details of the Keystone 9202 bracket that I’ve used in my ISA POST card design.

This has prompted me to create a proper place on my Github account to better manage storage of files that I’m pleased to share with the community. See ausandavno on Github.

To answer this question about the Keystone 9202, I’ve placed a Kicad footprint file, and 3D STEP file in the following location: https://github.com/ausandavno/Kicad_Misc

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Retro-CGA #6 – Character Font

Posted on January 31, 2020 by Andrew

The last post in this series covered the receipt of the Retro-CGA prototype circuit boards, and the soldering of all components onto one of the boards, making a completed prototype card:

This post covers the last step in preparing the card for use; the derivation of the character ROM and the loading of the character data into the ROM chip on the card.

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Retro-CGA #5 – Fabrication and Assembly

Posted on January 24, 2020 by Andrew

The last post in this series showed some of the detail of the Retro-CGA as it has come together so far, and ended with the preparation of Gerber files in preparation of having some prototype boards fabricated.

After a week or two of waiting, the fabricated boards arrived in the mail. This post documents the assembly of one of the boards into a completed prototype.

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Retro-CGA #4 – Design Features and Fabrication

Posted on January 3, 2020 by Andrew

The last post on the Retro-CGA showed the gradual progression from schematic design to  board build-up, summarising a period of several busy weeks.

This post acts as a summary of that whole exercise, showing some of the board design detail. More progression is made towards board fabrication and testing.

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Retro-CGA #3 – Initial Board Design

Posted on December 27, 2019 by Andrew

The last post in this series covered aspects of the initial schematic design of the Retro-CGA. This post will crack on with the initial board design, using the magic of pictures to show the detail of the board build-up.

I hope that you enjoy seeing the progress thus far on the Retro-CGA.

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Retro-CGA #2 – Initial Schematic Design

Posted on December 6, 2019 by Andrew

In one of my last posts I pondered the journey required to create an open-source video card inspired by the CGA card that I had repaired, in an attempt to preserve its historically-significant legacy.

In this post I will share the progress I’ve made on undertaking that journey, using the various guiding principles discussed in the initial post.

In what I presume will take months of effort, let’s launch into the design of the “Retro-CGA”.

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Retro-CGA #1 – Starting the Journey

Posted on November 21, 2019 by Andrew

If you have been following the ongoing saga of my CGA card, you would have seen the recent progress in repairing the extensive damage to the card, and getting the card running with Sergey’s Micro 8088. Although I haven’t yet tested the full features of the card, I’m reasonably confident that it has been successfully repaired.

Having jumped that hurdle, I am now contemplating the journey required to create an open-source video card inspired by the CGA card that I have, in an attempt at preserving the legacy of the CGA and allowing a means for future generations to create and learn about this historically significant video card.

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Learning KiCad; Designing and Building an ISA POST Card

Posted on November 19, 2019 by Andrew

The last post in my series on retrocomputing covered the testing of my repaired CGA with the Micro 8088. The process of troubleshooting took several weeks, and it became apparent that a handy piece of hardware to have would be an ISA “POST Card“. This type of card is designed to display a series of diagnostic codes that are generated by the BIOS as it reaches certain milestones in its execution. This would have been very handy to have as a means of verifying if the Micro 8088 is functioning normally and executing BIOS code.

It is possible to buy an ISA POST card off eBay, but in the back of my mind I am wanting to learn how to use the KiCad software package to design and produce circuit boards. This may be the perfect excuse to design a POST card using KiCad, and do a whole lot of learning along the way.

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Testing my repaired CGA with the Micro 8088

Posted on November 4, 2019 by Andrew

After repairing my CGA video card, and building Sergey’s Micro 8088 processor board and ISA 8-bit Backplane, I am now in a position where I should be able to test the combination of cards and verify if the CGA video output is working. I should also be able to find if the Micro 8088 is behaving correctly.

Join me after the break to read about the journey. Fair warning that this post is a long one. Hopefully you will find it interesting or at the very least entertaining to observe my failures and the strategies employed to work around them.

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