Calculator suitable to hack for LCD and keypad

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pmolsen

Senior Member
Have there been any postings about a brand of calculator that is suitable to hack to insert a Picaxe inside and make use of the keypad and screen.

I built a project some time ago using a standard keypad and the AXE033 LCD display but it is too big. I want to shrink it down and I thought there might be a calculator out there that could be modified.
 
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westaust55

Moderator
Not aware of anything discussed here in the past year along the lines you seek and a quick search of the forum (you had tried that yourself?) did not turn anything up.

What are the dimensions you are trying to achieve? :confused:
would not think most simple calculator keypads were any smaller than a 16-key keypad from an electronics store.
 
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pmolsen

Senior Member
I actually had in mind an older model. One with a bit of space inside. Just thought someone might have stumbled upon one that could be hacked. Inserting a standard keypad and the AXE033 into cutouts in a jiffy box (plastic circuit board box) requires a fairly large one. Most of them are about 2" high which makes the whole thing bulky.
 
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pmolsen

Senior Member
The AXE033 is about 80mm wide. But it is also the time to cut out the hole and do all the wiring etc.
 
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SilentScreamer

Senior Member
pmolsen said:
The AXE033 is about 80mm wide. But it is also the time to cut out the hole and do all the wiring etc.
Click to expand...
I expect even if you can find a calculator suitable it will take far longer to make it work than the time to use a bought keypad + screen (and any additional chips to link the screen to the PIC).
 
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westaust55

Moderator
I think you will have to "bite" (or is that byte) the proverbial bullet and select an enclosure/box and start from scratch.

Even if you found a calculator you will still have to wire up the keypad and display.

Years ago I took a keypad from a calculator for use in a reticulation controller i designed. Had to cut a few copper tracks and solder a couple of jumpers elsewhere to create a simple matrix for the keys as comes by default with keypads available form Jaycar and elesewhere.
 
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westaust55

Moderator
Andrew Cowan said:
This might be possible with a mobile phone, however...

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Click to expand...
Mobile phone displays need as a minimum (serial comms) about 5 signals and IC's to operate the LCD at the correct voltage. Colour LCD's in mobiles can use 14 or more signals with a parallel type of interface.
They are also gLCD modules so need a lot of program space to drive slowly.

So not in the same category as a serial character based LCD like the AXE033.
 
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westaust55

Moderator
@pmolsen,

I was in Jaycar (again :) ) today and had a look at the handheld enclosure I reference in post 5. Namely:
Sloping Handheld Enclosures - 150 x 95 x 28.5/49.5mm - Light Grey AUD$10.75 http://www.jaycar.com.au/productView.asp?ID=HB6090

The front 75% of the case is only 28mm high and the last part is inclined up to 49.5mm which would make the display easy to read.

An AXE033 display is 83mm wide and may fit well in the inclined opening (file the separate bezel part to suit) but you would have to separately mount the serial piggyback board within the case as it is 90mm wide and offset slightly.
 
hippy

hippy

Technical Support
Staff member
pmolsen said:
Have there been any postings about a brand of calculator that is suitable to hack to insert a Picaxe inside and make use of the keypad and screen.
Click to expand...
I'm a bit confused as to what you want to do -

1) Take what you have and fit it into a calculator

2) Modify a calculator to use its keypad and display

I don't know of any calculators which had any LCD text display which could be used to replace the AXE033 you have, the best-match gadget which does which comes to mind is the Psion II PDA ...

http://www.bioeddie.co.uk/models/psion-organiser-II-cm.htm
http://www.bioeddie.co.uk/models/psion-ll-organiser-lz.htm

I believe the LCD for the first is standard HD44780 but soldered direct to the PCB so might get a bit tricky to hack but should be possible. The keypad is probably standard NxM matrix scanning.

I got hold of a couple some years ago hoping to use them as PICAXE terminals but saw how the LCD was connected and went no further. I can take the back off one and have another look if you like. It may look easier now than then.

Its "serial interface" requires add-on hardware ( shift-registers / latches AFAIR ) so it's unfortunately not a simple case of take wires from three I/O pins and use it with SERIN/SEROUT while running a terminal emulator program on it.
 
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moxhamj

New Member
Just a thought, but it could be possible to use a calculator to display numbers without hacking into the display. If you can get into the keyboard and put 4016 cmos switches across each keypad, you can "press" keys with software. To display a number, 123, "press" the clear button then press 1,2 then 3. Then you don't have to worry about how the display works.
 
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manuka

Senior Member
Dr_A: That's a well worth running with idea for temperatures I'd say, although a lot of wiring may be needed for the diverse keys! The old calculator 1 + 1 = = = ... tallying trick can be handy for sequential counting of course- one used for decades. N.B. Many calculators have auto power off after 10 mins, & your tally may be scrubbed!

IMHO in general look for oldie but goodie serial organisers (& the like)that come with inbuilt terminal programs. Although cheap/free these are now getting a tad thin on the ground, but the likes of Casio PVs (Pocket Viewers) may appeal=> http://www.picaxe.orconhosting.net.nz/pvdemo.jpg .

You really can't beat a full display LCD of course, but for simple readouts don't forget diverse audio beeps/tones, or LED flashes/colours that PICAXEs can rustle up cheaply & efficiently.
 
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