Van Zijst's solution: a shield add-on for the Arduino Uno which includes a quick-change zero insertion force (ZIF) socket compatible with the Microchip AT28C256 EEPROMs chosen for the project. The act of writing, or 'blowing', data to an EEPROM requires a dedicated programming device, which are relatively specialised machines - and, thus, expensive. "In contrast to most newer EEPROMs they have parallel input and output pins for address and data, making it trivial to read from."
"These chips tend to be much larger and expensive than their modern serial counterparts that have largely replaced them," van Zijst explains - but there was a good reason to select the vintage designs for his projects. Today, EEPROMs - and EPROMs - are rarer, for a good reason.
Both, of course, were an improvement over PROMs, write-once read-many devices which needed to be discarded if any upgrades or modifications were required. If you want a general-purpose EEPROM programmer you'd be better off shopping elsewhere.A common sight on vintage hardware, EEPROMs are surprisingly chunky DIP-packaged chips which upgraded the older EPROM designs in being erasable in-circuit using nothing more than an electrical signal - contrasted with EPROMS, which needed the chip inside to be exposed to strong ultra-violet light from a dedicated eraser through a quartz window in the package.
Note that this kit is very much intended for people who have read my blog articles about how to read and write EEPROMs, and want to have a go.
Supporting software is available for free from my blog. It'll be of interest to anyone who might need such a programmer for a retro 8-bit hardware restoration or for other electronics projects.
I hope it'll be a fun and easy project, particularly for anyone who is teaching themselves to solder. It's very simple and straightforward (I hope!). maybe I'll learn from my mistakes and do better next time! What makes it special? If it's successful I hope to turn more of my home projects into kits that people can make for themselves. It's also a bit of an experiment in selling kits online. I've had enough interest from readers who would like to build their own, so I hope this project will be a convenient way for people to have a go themselves. Originally as a self-learning project which I subsequently blogged about. Note that it doesn't write EPROMs (with a single "E") as these require a much higher voltage for programming. It can read standard 28-pin ROMs, and read or write 28-pin EEPROMs. It is available as a kit, or fully assembled and tested. I've had feedback that soldering the ZIF socket over the DIL header could be a bit of a pain, so I've redesigned the PCB to be slightly larger, but better laid out for simpler assembly. This is version 3 - electrically identical to the previous version, but with a new and improved PCB. The kit includes PCB, 28-way ZIF socket (option of budget or high-quality versions), header pins, indicator LEDs (one for "Read" and one for "Write") and resistors. It's a simple EEPROM programmer shield, designed to sit on top of an Arduino Mega 2560.