Category Archives: Hardware

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 →

Posted in Computing, FPGA, Hardware, RetroChallenge, Retrocomputing | Leave a comment

More progress to report, after all

Posted on July 31, 2011 by Eric

I fixed several bugs in my code, and now the DIY4 can display the directory of an SD card and read and write files. It’s not perfect, as the first I/O fails, but subsequent accesses succeed. I’m using the open … Continue reading →

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Display contrast in DIY4

Posted on July 26, 2011 by Eric

The DIYRPN 4 calculator uses a 16×2 character LCD module. The choice of module was limited due to the desired physical width of the calculator. We chose a module made by Lumex. The module is specified for operation on a … Continue reading →

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Keyboard scanning on the DIY4

Posted on July 25, 2011 by Eric

I tracked down a bug in the keyboard scanning of the DIY4 today. I thought there needed to be a delay in the scan routine between writing the scan lines and reading the return lines, but it turns out that … Continue reading →

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Bit-banging FRAM on the DIYRPN 4

Posted on July 25, 2011 by Eric

I’ve written code that successfully reads the vendor/device ID and serial number from a Ramtron FM25VN10 SPI FRAM chip. I haven’t yet read or written data. The code is currently using GPIO bit-banging, but the hardware is designed to allow … Continue reading →

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Motherboard ethernet port went bad

Posted on October 19, 2010 by Eric

The onboard ethernet port of my Asus M4A785TD-M EVO motherboard went bad.  It was working fine, then all of a sudden quit.  Neither Windows nor Linux can detect that the Ethernet chip is even present, e.g., not even with an … Continue reading →

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