Casio data logger
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AWARD - This design has been judged the "best overall" at the Circuit Cellar Ink "Design 98" Contest sponsored by Microchip and Hewlett Packard.

 Alberto Ricci Bitti PIC based Casio Data Logger design

Bring the REAL world inside the Casio!

Now you can interface your Casio to the outside world!  Get lots of data from any kind of sensor, store it in Casio memory, graph it on the built in display in real time or apply any math function you like.
Do it anywhere, the unit works on batteries. Sophisticated processing, as regression or statistical analysis, are only a keystroke away. You can zoom, pan. list your data, or even transfer it to a PC.

V   N °C kgm A Hz lux hPa kWh %RH DP + this project = Cfx9850.jpg (5992 byte)
your real world sensors... ...and the casio analog interface... ...means your data easily graphed and analyzed


The calculator is left untouched, just connect the analog interface to the "program-link" plug on your Casio and start capturing data.

Tech facts:
>    reads up to 8 analog inputs at once
>    1 mV resolution, input range from 0 to 4096 mV (12 bits)
>    interfaces directly to a huge vaiety of sensors
>    battery operated, >200 hour operation from a single 9V battery
>    easy programming through the Receive(X) Casio instruction
>    easy to build, uses the popular PIC16C84 (16F84)
>    fits in a small plastic box as large as the calculator
<>    compatible with Casio FX9750 and FX9850, CFX9850

Files available:

my article on circuit cellar ink, issue 99, october 1998
The article covers all the technical details. It includes the schematic and parts list in case you would build one by yourself.
It also explains the Casio serial protocol and how to make a thermomether from a temperature sensor.
This is a .PDF file from the Circuit Cellar web site, you need the Adobe Acrobat reader to view it (download it free from

HTML on-line version of the same article published by EDTN network

click here to see the complete circuit diagram
same as in the article above  (xy_schem.gif, 52kB<)

the PIC16C84 (PIC16F84) source code
Fully commented, in official Microchip mnemonics. You need the MPASM assembler (free from to assemble it.

the PIC16C84(PIC16F84) executable only

errata - please note:
the schematics erroneously connect the led to the positive supply rail, connect it to the negative rail instead. Thanks to mr. Mark Pepper for discovering it.

Compatibility & call for testers:
I built the interface to work with a Casio FX9750. Thanks to mr. Paul Denham that succesfully tested it on its color CFX9850.
It should work unmodified with similar models (e.g. CFX9800) but I have not tested it. If you have tested it on any new model, please e-mail me. Thanks.

Got a TI8x - TI9x calculator?
Try the Sami Khawam's Texas Instruments PIC interface at

Teacher's delight
The Casio is immensely popular in schools. In the classroom, this cheap design lets the Casio capturing data from all kind of experiments. It can make learning physics, math, natural sciences more fun - and more effective.  The possibilities are endless - let's look at a few examples

  • With a torch and a photoresistor, discover the relation between distance and illumination.
  • Now use the light sensor to count how many people walks through the beam.
  • With two LM35, compare the rise in temperature of two Coke cans - one in free air and the other in a wool insulation.
  • Now place one LM35 in the classroom, and one out of the window. Compare the graphs of the two temperatures over 24 hours.
  • Build a force/pressure sensor measuring the resistance between a copper/conductive foam/copper sandwich. Try to linearize it.

Title: Casio data logger
electronic circuit
Published on: 2005-02-03
Reads: 996
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