Author Archives: Eric

Added serial port

I’ve added the DE-9S connector, TRS202ECN transceiver (equivalent to MAX202), and ceramic capacitors, which make up the TIA-232-F serial interface. The serial interface uses a female connector and is wired as DCE (Data Communication Equiment) to facilitate direct connection to … Continue reading

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RetroChallenge RC2017/10 final report

My RetroChallenge RC2017/10 project was to update and improve my FPGA-Elf. The resulting hardware may be seen here: I have succeeded in accomplishing my main goals for the project, which were: Update my FPGA-Elf design to use a currently-available, relatively … Continue reading

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Mounting rails for Elf

Richard Ottosen cut and drilled some mounting rails for me, out of some scrap wood. They’re standard Elf size, 3/8 inch wide by 3/4 inch tall by 6 inches deep, each with four 1/16 inch pilot holes for #4 wood … Continue reading

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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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PC boards for RC2017/10 are here!

My PC boards from PCBWay have arrived and look great! Time to get soldering.

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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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Second breadboard prototype

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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