Null modem for Casio FX850/880P

Many owners of Casio FX850/880P scientific calculators turn green with envy at the sheer simplicity of data exchange between two HP pocket calculators. These machines use infra-red data (IrDa) transmission to exchange data and programs without any additional interface. AIthough the FX850/880P has no IrDA features like its HP rivals, it can be used to communicate with another FX850/880P without problems. We show you how to do this the low-budget way by using the machine's se rial interface connector and a few lines of BASIC.