Category Archives: Computing

FPGA-Elf actually running PIXIE graphics demo

My VHDL reimplementation of the CDP1861 PIXIE graphics chip is mostly working!  This still image looks almost the same as the one from a few days ago: The difference is that now it’s being generated by the 1802 program (seen … Continue reading

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ELF-CMOD-A7 runs its first actual program

After removing one solder bridge, cutting one trace, adding one wire*, and changing a few lines in a Xilinx constraints file, My RetroChallenge Elf project has now let me successfully toggle in and run its first simple program, which is … Continue reading

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RetroChallenge board almost working!

Not everything is installed, but the power supply, data hex LEDs, most of the switches, and the composite video output are working. The switch for data bit 3 doesn’t work because I wired it to an analog input pin of … Continue reading

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Elf hexadecimal data display working

I just hacked up more VHDL code to get the Elf hexadecimal displays working. I’ve only tested the data displays, but the address should work as well. This probably doesn’t sound like much of an accomplishment, especially compared to my … Continue reading

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Elf switches and video

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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Parts from Digi-Key arrived a day early

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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RetroChallenge Half-TIme Report

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

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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