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1. 06:27 AM - Re: RS-232 and Navworx (Robert L. Nuckolls, III)
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| Subject: | Re: RS-232 and Navworx |
At 04:39 PM 11/8/2017, you wrote:
>
>Might be worth noting that NMEA0183 uses the EIA-422 (sometimes
>known as RS-422) not RS-232.
NMEA0183 is a digital language that can be conveyed
on RS232, 422, 485, fiber optics or even bluetooth.
The "RS" conventions speak to voltage levels, and
transmission lines and are totally independent
of 'language'.
RS232 is a single wire signal operating against ground
that swings above and below ground to represent "1"
or "0". That voltage may be as high as +/-12 volts
but I've built systems that ran quite happily on
+/-5v. I had one project that ran +5/=12 . . .
the exact voltage is not critical, it's he
transition from + to = and vise versa that carries
the information.
RS422 is a balanced pair of wires where the signal
polarities alternate between the two wires. RS422
transceivers generally operated in the 5v world so
the voltage between the two lines is generally 5v
with data being carried on polarity reversals.
There are integrated circuits designed to translate
422>232 or 232>422 . . . either convention can
carry NMEA0183 messages . . . or any other
protocol.
Bob . . .
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