On Wed, 30 Dec 2020 18:52:14 -0500, Dennis Lee Bieber wrote:

> On Wed, 30 Dec 2020 18:31:07 -0000 (UTC), Martin Gregorie
>  declaimed the following:
>
>
>>Ignore the gpio lines: Just get a standard a USB-serial adapter. Each
>>supports a single serial line, so get one for each device with a serial
>>port that you need to connect to the Pi and either plug them directly
>>into the Pi or, if you run out of USB ports, via a USN connector block.
>>
>>
>  That doesn't answer the OP's actual request -- they want the ports
> physically on the R-Pi to be VISIBLE on the host (desktop/laptop)
> computer that is connecting to the R-Pi.
>
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.

Once that's done  the rest should be fairly simple programming. If the OP
speaks C, then whipping up a program based round the poll() library
function is pretty straight forward, not the least because it avoids
having to write any multithreaded code.

Don't like C? Write it in Perl or, probably, Python instead.

Java isn't really a starter for this job since it can't handle serial
ports without helper processes, which would have to be written in C, Perl
or Python.


--
--
Martin    | martin at
Gregorie  | gregorie dot org

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