Author Archives: Eric

Elf switches and video

Posted on October 22, 2017 by Eric

I did test the switches wired to my RetroChallenge project solderless breadboard last night, and they work fine. Today I worked on the monochrome NTSC composite video output. First I got the video counters working, and generated a frame with … Continue reading →

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Second breadboard prototype

Posted on October 21, 2017 by Eric

Since my PCBs aren’t likely to be here before Tuesday evening, and I’ve abandoned the 5×7 matrix LEDs, I’ve had to throw together a second hardware prototype using the HP 5082-7340 hexadecimal LED displays. In this photo, it is running … Continue reading →

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Parts from Digi-Key arrived a day early

Posted on October 19, 2017 by Eric

Thanks to Digi-Key and UPS, parts for my RetroChallenge project arrived a day early. I just got back from my client’s product launch party, where I had entirely too much excellent food and drink, so I’m not actually taking advantage … Continue reading →

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Schematic and PCB layout finished, boards ordered

Posted on October 17, 2017 by Eric

Late last night I finished the schematic and PCB layout, and ordered boards. As soon as I woke up this morning I realized that I forgot to deal with the 5V CMOS output of the TIA-232-F receiver feeding the non-5V-tolerant … Continue reading →

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RetroChallenge Half-TIme Report

Posted on October 16, 2017 by Eric

Although I got the LTP-305HR dot-matrix LED multiplexing working, it doesn’t look anywhere near as nice as the original HP 5082-7340 or TI TIL311 hexadecimal displays. I’ve decided to drop my original plan to use the LTP-305HR displays, and use … Continue reading →

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Full multiplexed display for RC2017/10

Posted on October 7, 2017 by Eric

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

Posted on October 6, 2017 by Eric

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

Posted on October 5, 2017 by Eric

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

Posted on October 3, 2017 by Eric

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

Posted on October 3, 2017 by Eric

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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