Author Archives: Eric

Full multiplexed display for RC2017/10

I’ve now got full multiplexed display operating on the breadboard prototype for my RC2017/10 project: I also shot a brief video showing chaning hexadecimal values. There are six 5×7 displays, physically all in one column to fit the breadboard, but … Continue reading

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RC2017/10 finished wiring LED matrix

I finally finished wiring the LED displays on the breadboard prototype. What a mess! The LTP-305HR displays are still being driven basically statically, with only one column of LEDs (on both logical rows) being illuminated at a time, and only … Continue reading

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More LED matrix prototyping

I’ve added a second breadboard to prototype with all six LTP-705HR displays, and the additional sink and source driver needed. The matrix is wired, but not all of the drivers are hooked up.

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FPGA-Elf display drivers and multiplexing

For my previous FPGA-Elf, I used actual hexadecimal displays as per the Popular Electronics construction article. The only hexadecimal LED displays still made are from Broadcom/Avago, don’t have the integral red filter, and cost around $40 each. Used or NOS … Continue reading

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RC2017/10 project: affordable FPGA-Elf

For the RC2017/10 RetroChallenge, I will update my FPGA-Elf to run on a relatively inexpensive FPGA board, and make PCBs to provide the necessary I/O interfaces.  I plan to add the equivalent of the CDP1861 “PIXIE” graphics. At the conclusion … Continue reading

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unintentional nondeterminism in a Python program

There’s a Python 3 program I’ve been developing off-and-on for three years now. The program takes an XML file as input, does some processing, and outputs a binary file.  After some recent changes, I find that the program hangs. If … Continue reading

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Vonada’s Electrical Engineering Maxims

A list of electrical engineering maxims by DEC Engineer Don Vonada: There is no such thing as ground. Digital circuits are made from analog parts. Prototype designs always work. Asserted timing conditions are designed first; unasserted timing conditions are found … Continue reading

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RC2016/10 success? Failure? I’m not sure.

As seems to be usual, my stated plans for Retrochallenge didn’t come to fruition.  Several times I’ve planned to do vector graphics stuff, and not done it, so this time I planned to do something else, USB bubble memory. Of … Continue reading

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Vector display working!

Some years ago I obtained a few Data Check 5045 digital vector displays from HSC Electronic Supply. Data Check bought the product line from HP, where this model had been the HP 1345A. HP used these in some of their … Continue reading

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Vector display!

Some years ago I obtained a few Data Check 5045 digital vector displays from HSC Electronic Supply. Data Check bought the product line from HP, where it had been the 1345A. HP used these in some of their own test … Continue reading

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