In SX Microcontrollers, SX/B Compiler and SX-Key Tool, George Herzog wrote:

Having just come back from walking the dog, it occured to me that this configuration is not limited to SERIAL IN.  B&B sells RS-232 to RS-485 converters for about $75USD!   By using this to convert RS-232 SERIAL OUT from the BasicStamp to TTL, you can then hook up to a 75176 chip to drive RS-485 WITH ISOLATION.  The cost are less than $8 for chips plus a 5volt wall wart.

In fact, it may be a simpler design and with only two Optoisolators.  It is really a winning situation for long lines and possible shorts or insertion of high voltages.  It can be done at both ends so that the wire is completely isolated from devices.  If some incident hooks up 110VAC to your cable, you limit damages to about 4 chips and your power supply.  Very robust, easy to configure.

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