The first basic job handled
by the library is to send and
receive numbers to and from
the calculator. TI calculators (at
least the ones for which this library is written) use "silent
transfer" which means that the calculator does not have to
be in a special mode to get or send numbers. The two
routines that handle the protocol are sendNum and
is the Data1 line; and the sleeve is ground. When idling,
both lines are held high by the Arduino internal pull-up
resistors.
To send a zero, the sender pulls the Data0 line low.
The receiver then pulls the
Data1 line low to
acknowledge, then both lines
go high. To send a one, the
sender pulls the Data1 line low
and the receiver acknowledges
by pulling the Data0 line low.
These are handled by the
library's internal functions and
do not need to be accessed
by the user directly.
Figure 1 shows a data
cable that I made by buying a
TRS cable on eBay and cutting
it in half. Finally, in my
experience, the TI 83+ cannot
handle the current drawn by a
direct connection to the
Arduino, so I put a 1K resistor
in series with each data line;
all calculators are happy with
this arrangement. I connected
these to two Arduino digital
pins.
Using the Library
Copy the library folder
Arto TI to the Arduino library
folder then insert #include
<ArtoTI.h> into the code. Use
the constructor before the
setup function:
ArtoTI a(8,7);
where "a" is the name of the
instance, 8 stands for the pin
connected to the tip and 7
stands for the pin connected to
the sleeve. Once that is done,
you can call any public
function (see ArtoTI.h or the
guide included in the library
folder for the available
functions).
May 2014 49
FIGURE 2. Schematic.
FIGURE 1. Wiring.
