2.5 mm Jack Plug Connection

The calculator uses a 2.5 mm stereo jack plug for the physical connection as only three lines are required for data communication, Tx, Rx, and ground.

After a little reverse engineering I managed to figure out which pins were for transmitting, and which for receiving. This diagram shows how the jack terminals connect to the pins on the MAX232 chip.

Soldering the Jack

Here is a diagram showing how the outer contacts relate to the inner soldering connections. Students generally find this very useful.

The jack socket on some Casio calculators is often inside a recessed hole, so you should make sure that the jack plug you get fits into it.

This Article Continues...