“Driving vintage HP HDSP-2000 Alphanumeric LED displays with a retro EPROM 8051 Microcontroller.
I made this project because I love Vintage Hardware and wanted to make something cool with the LED displays and an old 8051 that I had. End goal is to implement Character LCD emulation on the GPIO so it can act as a drop in HD44780/HD66702 based Character LCD replacement.
I also wanted to take on the challenge of optimizing the code to run fast enough with the limited speed and peripherals of the 8051 Microcontroller. As a result, I got to learn the 8051’s memory map with more detail in order take advantage of the bit-addressable RAM on the chip for a fast bit-banged SPI output, which was pretty fun.
Features:
Can display the US ASCII character set, as well as Japanese Katakana and Hiragana using a custom 5x7 pixel font stored in the program ROM. (I love Japanese, so had to get it in there!)
The ROM character sets are based off the those in the HD66702 LCD driver chip found in many Character LCDs.
Communicates with the displays through an optimized Bit-Banged SPI-like protocol utilizing the the 8051’s bit-addressable memory for speed. Based on code found here but modified for SDCC.
Written in C and compiled using the Open Source Small Device C Compiler (sdcc)”