What's IR Messenger ?
IR Messenger allows you to chat using an easy-to-build home-made infrared link on a TI89 calculator.I am not responsible for inappropriate use of this device.
Great, how will we do that ?...
You'll have to build by yourself the electronics allowing your TI89 to send and receive infrared signals. It's simplified to the maximum, unlike other existing devices, most parts are cheap and found everywhere. You won't even have a microcontroller to program ! The main part of the work is achieved by the software running on your calculator.It's NORMAL that the interface does not work using the default communication system of your TI89. You should use the software provided on this site only (or equivalent !)
Software
So as to make the hardware easy to build, the software achieves the most part of the work, it handles the serial transmission. It has been written in C using TIGCC, the source code is included in the archive.Use the irsetup program to install the software into your calc, then you can use Diamond+CLEAR to switch between its screen and the normal calculator's screen. The keystrokes are the following :
- Diamond+CLEAR : switches screens
- CLEAR : clears the message you are editing
- ESC : leaves
> Download
Hardware
The hardware has been made very simple. It only send IR pulses at 30kHz when it gets an high state on a wire of the link plug and sends back a logic state on the other wire according to the IR signal it receives ! The rest is done by the software.The integrated circuits are classics 555 and 4011, available everywhere, and the IR reception uses a dedicated circuit, the TSOP1730, which shouldn't cause problems of availability nor price (about 3 euros).
After you've built two circuits, you'll have to tune the transmission frequency using the only potentiometer of the circuit. Connect a frequencymeter between the pin 3 of the 555 and the ground and adjust the potentiometer until you get a frequency of 30kHz.
The connection with the calculator is not straightforward. Using standard male 2.5mm jack plugs, there are too many poor contacts. The best solution is using a female 2.5mm stereo jack plug and connecting your circuit with the TI's cable.
> Schematics diagram
> Jack plug pinout
> PCB
> Photo gallery