The goal of this project is to develop a useful, reliable, and inexpensive networking system to extend the use of graphing calculators in the classroom. This system will involve developing a manufacturing process to make the required hardware components, as well as writing and adapting most of the software needed to use the hardware.

The target date for completion of this project is Monday, November 4, 1999.

Most of the work will be done at my home. The hardware will be assembled using mail-order parts from Mouser Electronics and/or Kycon Connectors. Some preliminary parts will also be purchased from Radio Shack, as it is as convenient as it is overpriced. Software work will be done at my home computer, as well as research and most mentor contact. Testing and debugging the system will be done at Mountlake Terrace High School, which has by far the largest concentration of graphing calculators in the area.

I chose this as a project because I enjoy working with electronics. When I got a graphing calculator I wanted to make my own calculator to computer link to put games on it. I found the project to be very interesting and enjoyable. I doubt that I saved money building it myself instead of buying the official link from Texas Instruments, by I learned much more.

Prior to the official start of this project I had worked on a hardware link between a calculator’s link port and a computer printer port. The process involved takes about an hour for assembly, including the time required to etch a custom circuit board. The other major electronics project I worked on in the last few months was making an electronic pitch pipe, which would play the desired note into a pair of headphones. I will be building directly on the work of the former project and indirectly on the experience of the latter.

Developing the software will be somewhat more difficult, as I have had no experience writing software for graphing calculators. This part will be made easier by the fact that the basic network software has already been written for the TI-85, and will only need to be tailored to run on the TI-83 and TI-82.

This project will give me a working understanding of how to write software for the calculators involved. I will also be working with a few microchips made by Phillips Semiconductor in my hardware designs. I will discover how they work while designing the hardware around them.

Texas Instruments graphing calculators (TI) are designed to link together two at a time. The provided cables and the way the calculator handles the link port have set this definite limit. This limit, however, only holds while using the TI with its original software.

The Inter-Integrated-Circuit (I2C) bus protocol developed by Philips Semiconductor uses three wires to network together over a hundred devices. The link port on a TI also has three wires. Given the right programming any number of TI’s can be linked together at once, providing previously unconsidered possibilities.

This field has been pioneered by Osma Suominen, a Finnish student. The software, called the MultiMaster Bus (MBus) has be written only for the TI-85 calculator and consists mainly of the assembly routines that must be used to create network programs. It also includes several testing programs and a chat program (mchat). I will be sending all of the programs that I write during the course of this project to Osma, who will hopefully place them on his webpage. If the time is available I will write my own webpage showcasing this project.

The goal of this project is to extend this preliminary work to the point where it can be used effectively as a teaching aid.

After talking to a few math teachers at MTHS I decided that writing a system to process multiple choice quizzes would be the best application. Under this system each student calculator would have to be loaded with the main quiz program, initially through a computer link. Multiple choice problems could be placed on an overhead projector or written on the chalkboard. Each student would select their answers from an on-screen display and send their answer over the network to be graded on the teacher’s calculator.

I am still open to other options for this stage. The program will have to be written for the TI-85, TI-83, and TI-82.

After each technical step the system will have to be tested at MTHS. Most steps will only require a few calculators borrowed from other students. To test at this level a simple physical wiring scheme is needed to connect two or more calculators together at a time. For initial software debugging a hub capable of connecting four calculators will be more than sufficient, but eventually the system needs a full trial run as part of a teacher’s lesson plan. Hopefully one or more teachers will decide that the system is useful enough to keep at the school.

The major part of this project is rewriting (porting) the software so that it will work on calculators other than the TI-85, which is currently the only one supported. I will have to learn how to transfer the assembly routines to the TI-83 and TI-82. This work will also make it possible to write a program allowing the transfer of files between the supported calculators, which is not supported by the standard link protocol.

In order for the networking system to be best integrated into the classroom it must be physically possible for each calculator to be wired to every other one. Simply wiring all of the hubs together will not work, because the nature of the signals being sent through the wires limits their effectiveness to a few meters. Another obstacle involved is that the license to use the I2C protocol is legal granted only with the purchase of Philips I2C components. The most straightforward way to eliminate both problems is to add a Bus Extender (Philips part # 82B715) to each hub so that the signals have the strength to go across the room. A much more visually appealing system involves using an Infra-Red transceiver on each hub. This, however, would be much more complicated.

A basic necessity required to do this project is the capability to send files from a computer to a calculator. This is done through a link cable. One can be purchased from Texas Instruments for $25. I opted instead to build one from schematics available on the Internet. I’m sure I spent at least $25 on all the parts I ended up experimenting with, but I gained experience. I have improved my manufacturing process to the point where I can now make a durable, working link cable in about an hour. At least one link will be included with the complete networking system for normal operation. A prospective improvement is to find a good case to put the circuit board in to make it look more professional.

The third MTHS competency which involves the processing of information will be addressed by gathering and using the required ideas and schematics I need to create a physical product. Obtaining peer level advice by conversing with members of the TI Hardware Newsgroup, as well as coordinating with teachers will fulfill competency six (communication).

I will use thinking skills (competency seven) while making judgments in how I address any problems that come up. The added experience of working individually should naturally enhance my ability to work alone (competency nine); in such cases as this, though, where I enjoy what I am doing, I have little problem directing myself.

This project involves understanding and using modern electronic technology. Augmenting the function of existing electronic devices is not a use that enhances the human environment - as stated by competency twelve - but it provides experience which may one day be turned to that end. The specific scientific concepts involved (competency sixteen) include operational concerns, such as the behavior of electric current in circuits, and construction principles, such as the reactions of building materials to high temperatures.

The specifics of how the system will be used in the classroom are to be developed in the later stages of this project with the help of the aforementioned MTHS math department. The nature of this project also allows a very natural extension into executing my presentation: I can pretend that the panel is taking a math quiz. This project will be considered complete once a classroom test run has gone smoothly.

Addendum: My mentor, Rick Jonas, is a manufacturing engineer at InterMec Corp. The company specializes in information services, and uses radio transmitters on many of their products. It is possible that I will be ordering some parts from them to build remote linking 4-way hubs.
 
 
 
 
 
 
 
 

Timeline

Week of: To do:

April 19 Test TI-85 routines and mchat program

April 26 Examine written TI-85 MBus routines

May 3 Build a 4-way hub

May 10 Research writing TI-83 assembly code

May 17 Finalize link cable construction

May 24 Research hub extension possibilities

May 31 Port MBus routines to the TI-83

June 14 Research writing TI-82 assembly code

June 21 Build networkable hubs

July 5 Port MBus routines to the TI-82

July 12 Write a TI-83 quiz program

July 19 Port quiz program to the TI-85

July 26 Port quiz program to the TI-82

August 16 Post a small webpage describing this project

September 6 Test networked hubs and quiz program in a classroom