This circuit can be used to “tap” the communication on the link port between two TI graphing calculators. It should work with any TI calculator that has a link port. I tested it with two TI84+.
Everything the TI calculators say can be viewed using a serial port terminal (like hyperterminal), as if you are watching a webchat between two people, only then in hex code...
Use the document at
http://www.ticalc.org/archives/files/fileinfo/247/24750.html
to understand what the calculator is saying. (on-line version:
http://zastava.student.utwente.nl/linkguide/index.html
)
(I did not write that document, I only made this circuit)
First “flash” the PIC16F628A with the hex code (see below for download), then build the circuit. If all is working you should get
readable text in you terminal (4800b 8n1).
Then connect 2 calculators and send data from one to another. (2nd link, transmit,
etc.) Data direction does not matter. Sleeve of both connectors should be connected to ground. If you don't see any communication, check the connection to the calculator. It's a 2.5mm stereo jack plug, but the housing of the calculator might not allow it to fit if the housing of the connector is too big. The connector shown in the picture above is to big. If you want to be sure, use the connectors from a real TI link cable. Connectors from cellphone audio adapters might be small enough too.
(GR is short for "Grafische Rekenmachine", Dutch for Graphing Calculator.)
For those watching closely: Yes, thats a TI84+ saying it's a TI83+, according to the linkguide. I don't know why it does that, maybe because I'm using the TI83 linkport. And yes: I'm sending Pi, stored in var A, to GR 2. Longer transfers work fine too, there is no lenghth limit.
If you watch closely you can see why I have 2 TI84+. This image can be enlarged in the same way as the others.
This connector fits. Barely...
proton + picbasic
HEX (PIC16F628A)