Psion Series 5 RS-232 Serial Port

The nice thing about the Series 5 is that there is easy access to the serial connector pins and plenty of space for modifications inside the unit. When I bought this pre-used unit, it did not come with a serial cable, and therefore I was very tempted to install a Bluetooth module to convert the serial communication to Bluetooth. I found some wonderful modules on auction sites that sell for as little as two pounds, which convert serial communication to Bluetooth. However, before making modifications or hacks I decided to research what this palmtop already had and was capable of.

As we can see from the circuit board, the communications port has tracks leading to the MAX3212 integrated circuit (IC) manufactured by the Maxim Corporation. It is an RS232 transceiver for battery powered palmtop computers and has power saving features. If there is no signal on the receiver input pins, then it shuts down its drivers reducing its supply current to 1-µA. This IC has three drivers and five receivers.

For the Bluetooth hack, one simply needs connect to Tx, Rx, and power supply lines to the Bluetooth module.

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