Product: Domino 1 and 2

Interfacing with an RS232 Driver


Date: 8/31/98

Introduction: The Domino modules come equipped with a serial interface that offers RS-485, RS-422, or RS-232A communications. Some applications may require a full RS-232C interface. This can be accomplished easily by using a Maxim MAX232 (or equivalent) transceiver and a few passive components.

Background: Domino 1 and 2 modules can communicate with other serial devices at up to 19,200 bps. It can be connected in one of three configurations: RS-232A, RS-422, or RS-485. The Domino 1 and 2 RS-232A output can communicate with most PC-type serial devices which normally handle RS-232C provided they can reconcile receiving the lower-voltage transmit level of RS-232A. RS-232A operates from 0 to +5 volts where RS-232C operates from –12 to +12 volts. The following schematic shows how to connect such a device.


How it works: By using any of Basic-52’s PRINT commands ASII characters will now output through the MAX232 transceiver and will be at RS-232C voltage levels. All serial commands asking for ASII characters such as the INPUT and the GET command will now be able to use RS-232C. The voltage divider on the RX- pin is so the Domino doesn’t get any false inputs.