On a sunny day (Sat, 19 May 2018 18:05:22 +0000 (UTC)) it happened Martin
Gregorie  wrote in :

>On Sat, 19 May 2018 13:37:29 +0000, Jan Panteltje wrote:
>
>> If you use the ptlrc commie-nuke-aid-ion program just connect tx and rx
>> together at the other end and type something,
>> should echo each character, confirms that your side is working.
>>
>Thanks for that. With Rx and TX shorted together at the stereo jack the
>AXE027 adapter cable is successfully echoing test strings back through
>ptlrc  - so the cable is working. This works both on my RPi B (original
>512KB version, Raspbian) and on my Lenovo T440 (Fedora 27).
>
>However, that form of loopback isn't working with my code. so I've
>probably got the serial port bit settings wrong, since the code works
>correctly when talking to a target emulation program over a socket
>session.
>
>> Important is to get the BAUDRATE correct.
>>
>On your code it loopback works OK at both 4800 and 9600 baud.

Yes, but I mean the baudrate of that thing you are connected to,
You need to know what speed that is.
There are devices thar will autmatically detect baudrate, and
then send back at the same speed, but that is not very common.

>> Often programs send some sort of hello message on powerup.
>> So see if anything happens in ptlrc when powering up that thing.
>> If it is unreadable try an other baudrate, and repeat.
>>
>I'm still going to talk to the Dittel agents about the KRT2 signal levels.

In an other reply I mentioned the difference between RS232
and the USB to logic level adaptors,
the ones with RS232 (D connector such as that Dittel thing you want to connect
to)
use inverted logic, also those drive the signal negative,
not sure your logic level interface will stand that.




>In the meantime I'll review my serial port settings in comparison with
>yours. This is a little puzzling, though because a while back I had the
>port handler working well when driven by a glass teletype emulator
>written in Java and using a real RS232 port connected to a system running
>Microware's OS/9 at 9600 baud, so it looks as though I'm using port
>options that worked with a full RS232 cable but not on a 3-wire link.

I was thinking if I was in the boonies and had no other option
and HAD to use the non inverting cable and IF it did not blow up on real RS232
signals on its input,
then MAYBE I would xor ptlrc output bytes with 0xff and same for input bytes to
force the invert ;-)

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