On Thu, 31 Dec 2020 00:58:57 -0000 (UTC), Martin Gregorie
 declaimed the following:

>It answers the first part of his problem: getting signals to and from a
>user process to a D-9 or D-25 serial port without having to build
>something on a GPIO expansion card.
>
 A 5-pack of TTLRS232 level shifters is available for only $6 via
Amazon (US).

 SparkFun has one that includes the DB-9 connector for $16
https://www.sparkfun.com/products/449 Other than running wires between the
R-Pi and the unit there isn't much to "build" (and this one likely can be
mounted in a suitable hole in a chassis).


--
 Wulfraed                 Dennis Lee Bieber         AF6VN
 wlfraed@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/

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