Nuts and Volts - May 2014

While the article gave good basic information, I found it lacking on three counts. First, it was centered around a PIC and I needed the code for an Arduino. Second, the language utilized was Great Cow Basic; I needed C (and a more robust implementation that did not rely on global variables — a known problem with GCB). Finally, the code in the article was only a demonstration of its potential; I needed detailed routines. For example, I needed to send numbers in my code and did not want to be responsible for converting them to strings first. That is what computers are for!

My first thought was to look online to see if anyone had solved this issue before I attempted to reinvent the wheel. I was disappointed. The only C code I found was similar to the GCB implementation and poorly written (unless they were deliberately obfuscating the code). I would fail one of my students if they wrote code that declared variables in the middle of a program rather than at the start of the routine!

So, I have written my own code in the form of an Arduino library which is available at the article link. The code will automatically detect the calculator that is attached: TI 82, 83+, 84+, or 86. The TI 82 does not support silent transfer, so it is not supported by my code at this time. After startup, you may send or get any variable (A-Z on 83+/84+, the 86 supports longer names) via silent transfer, and you may send any TI command that the calculator accepts. List sending is also supported and, of course, data plotting.

For an excellent guide to the protocols, go to TI- 73...V200 Link Protocol Guide v1.4 by Tim Singer and Romain Liévin at http://merthsoft.com/linkguide/ and choose the 83+ or 86. For the command codes, go to http://merthsoft.com/linkguide/ti83+/keys.txt or replace 83+ with 86 for those codes.

Protocol and Wiring

The August 2013 article has a good description of the basic protocol, but I will summarize it here. The TIs communicate over a serial two line (+ground) communication link. The cable is a 2. 5 mm (3/32") TRS cable. The tip of the connector is the Data0 line; the ring

While microcontrollers have grown to be very powerful, sometimes you need math functions that are not available or graphic capabilities that are complex to program. The popular TI (Texas Instruments) series calculators (TI 83+, TI 84+, and TI 86) have these capabilities and are often found lying around the home unused. I was looking for such a device when I was inspired by the August 2013 issue of Nuts & Volts which had an article by Thomas Henry about interfacing a PIC microcontroller to a TI 83+.