NOTE: This site is an archive of circa 2001. It is here for historical interest only; my life has changed a lot since it was created, and I can no longer maintain the contents. -Bryan

The Expander2

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Welcome! This is the official website of the Expander II (E2) project, which has produced a 512kb memory "expander", with fully featured module port, for the TI-92, TI-86, and TI-85 graphing calculators. The Expander will allow you to carry around up to 512kbytes of your favorite calculator programs in a small, inexpensive portable device. The site contains a ton of information, so please explore via the links above!



Welcome visitors. Please read the news below for info on the E2 semi-resurrection.

Out of curiosity I checked on parts availibility for the old E2 design. The world of electronics moves pretty fast so there is good news and bad news. Good news: the AT90S1200 microcontroller is still availible from Atmel. The bad news is the AT45D041JC has been discontinued (this was the flash EEPROM used in the E2). The E2 (and the TI calculators) run on 5V, and Atmel no longer manufactures 5V flash EEPROMs, so to build an E2 device today, you will need to add some voltage conversion circuitry and use a 2.7V memory such as the AT45DB041B (512kB). Some more good news: in the 5 years since the original E2 design, Atmel has built much larger flash memories... It may be possible to use the AT45DB642 (which holds 8MB).

Heh... If I did the design today, I'd probably try to use those USB keychain memories that are availible everywhere.

Anyway if there is interest, I'll try to investigate the 2.7V -> 5V stuff. I am also considering an E2 mailing list, but for now let's use the forum on Morgan's post...


Wow. It's 2004 now. Morgan Davies from tracked me down to ask about the status of the E2. Out of nostalgia I found a backup and, as you can see, put the old site on colo. I have also GPLed the E2 AVR source code. Please note that any non-jumbo text on this site is out of date, and that I am no longer actively supporting the E2 project. However, there should be enough info here for those with moderate electronics skill to build their own Expander2, or even sell kits or finished units to others.


Today I finally finished updating all of the driver and source code zips with the new site and e-mail information, and re-released them to I have also posted experimental TI-92+ and TI-89 drivers made several months ago by someone with a conversion utility. While I seriously doubt they work, I am posting them for those interested in trying. I have also posted the source sent to me by those working on the TI-83 port. It is not finished, but it is very close and I encourage any TI-83 programmer that is interested to finish it. All of this stuff is on the download page. This update is probably the last that will ever be made, however I will of course continue to sell E2s. I have several other exciting projects under development, so if you haven't already I invite you to browse the main site after you're done here. Thanks to everyone who has stopped by for the tremendous response this project has received.


After several months without any updates, I've revisited the E2 website and decided to overhaul it. Many people have complained about reliability issues with the old server on so the entire site has been moved to this new location. The E2 project is finished at this point, and I do not expect to make any modifications to any of the code or hardware in the future. There are currently over 200 E2s in existance and the continued interest in the project amazes me-- the old site had well over 30,000 hits. I am still accepting orders for E2 AVRs; if you have not yet explored the site, please do so as it will hopefully answer most of your questions. I am in the process of a site-wide redesign to make Horizon Technologies easier to navigate and more professional, so please bear with any growing pains. I am going to release new versions of the E2 drivers to reflect the URL change, and to supply people with my new e-mail address, Thanks for your interest in the project, and if you have any questions or comments please feel free to e-mail me!

[Horizon Technologies]