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Sweet little beastie!!

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Senior Member
Nov 25, 2001
Niagara Falls, Ontario, Canada
Hi guys,

Just got this old skool pocket computer for a couple of bucks at a flea market, and when I started realising what I could do with it, I was like "w00t, the alt mod guys would love these"

It's a Sharp EL-5500III, a programmable calculator more or less, but with a pretty powerful built in basic. It only has a one line matrix display, and only 6K of RAM, but there's one thing that makes it a real treasure. It's got an I/O port. Now it's not RS232, and I don't know the bit rate yet, it's a TTL level serial interface, and I think it would easily drive something like a MAX 232 chip.

What this means is that you can interface it to a PC as a kind of one line terminal, and there's all sorts of cool things you could do with one of those. Of course you have to write the proggy on the thing to communicate, but I think 6K should be enough to fit that into.

Here's just some of the ideas I've got for it so far.

Mount it on the dashboard of the car as an interface to a MP3 player PC, (displays track info, lets you choose track etc)

Strap it to your arm as an input device to a homebrew wearable. AMD make a K6 based chip that has everything on chip, like a complete mobo and CPU on chip, with one of those you could make a linux based wearable, arm mounted keypad interface with this little sucker, and buy up a broken down vid camera or something for a display to make a back projection visor display device.

Get an 8 input analog to digital chip and a parallel to serial convertor and have it cycle through 8 temps mounted on the front of your case.

etc etc etc.

I wish I had about 5 or 6 of these things, I just keep thinking up cool stuff to do with it.

Many Sharp models besides the EL-5500III have the same interface, some have got more or less features, you could probably do something similar with any of them.

So guys, look out for these and similar old pocket computers, (I think HP did some that might have an useable interface too) they might give you an easy to use display and keypad for a really cool mod.


Road Warrior
wow thats really cool. i have a calculator that has the exact same setup, colors and buttons. that looks like a lot of fun. if you could get it to run a mp3 player that would be awsome. it would be a nice retro look
hmmm, I've got the larger screened EL-9300 version whcih also has a io port, it was used to drive a printer for teh graph mode. sounds like you could be on to a winner.
Tandy had "badge engineered" Sharp models, their PC-1 also called something like the TRS80 pocket was a shapr, also the PC-2 3 and 4 were as well I think.

They also had an RS-232 interface for them, which may still be available from them special order. So if hacking up cables isn't your specialty you still might be able to use these.

As far as I can see, the connector is a standard 0.15 single inline pin socket connector, so any row of salvaged header pins, or an IDC socket with pins shoved in it, should work, you'll need a basic RS232 chip though. Look at the application data sheets if you're not a circuit figurer, probably it's all spelled out for you, with a reference design circuit that is just what we need.
Looking at the other models there's some really sweet ones with far more RAM, multi line displays and graphics modes.

(jealous) like the one nixie has (/jealous) :D nice!

Road Warrior