5i25 + 7i73

Is the 7i73 powered? I guess that your BoB does not power it through the CAT5 cable?
(And if the 7i73 is powered from a separate 5V, is it jumpered for that)

Is the 7i73 powered?

OUPS - my fault.
Sorry! didn't think about that

Powering the 7i73 did not change anything (a red led shines after powering on, so I think I did that right) - no reaction on "show pin".

I tried standard patch cable, as well as crosslink cable - as I don't know, whether I connected the signals on my bob right.
As no test succeeded, I disconnected the 7i73 and connected an oscilloscope instead.
I thought, on issuing the show pin command, I should see some spikes on the smart serial lines - but there was no rumor at all ...

... and as I don't know the right command syntax, I tried "show pin 7i73" as well as "show pin hm2_7i73" according to the fact that "show pin hm2_5i25" shows some output for the main card.

I don't know, how to continue. Any help is very appreciated.

Probably a pinout issue
(Also that looks like a jack with an Ethernet transformer, if so that will not work)

freeby.mesanet.com/7i74sch.zip

might help

There would be no hm2_7i73 pins but

halcmd show all | grep 7i73

should show all 7i73 pins/parameters

Thank you for your attention!

Previously I overlooked the stars in the command, so I tried all variants again.
No change.

"halcmd show all" issues an error like "Unknown 'show' type 'all'

Am I right, that a show command should give some spikes on the oscilloscope connected to the smartserial lines?

Thanks for the link - I'll dive into it
.

Also that looks like a jack with an Ethernet transformer

How can I verify, that I got the wrong jack and which one will be appropriate?

by the way - I used this connector

halcmd show all works for me: (I dont have a 7I73 here but do have another sserial card=7I69)

peter@pcw-HP-EliteDesk-800-G1-USDT:~/linuxcnc/configs$ halcmd show all | grep 7i69
26 bit OUT FALSE hm2_7i95.0.7i69.0.1.input-00
26 bit OUT TRUE hm2_7i95.0.7i69.0.1.input-00-not
26 bit OUT FALSE hm2_7i95.0.7i69.0.1.input-01
26 bit OUT TRUE hm2_7i95.0.7i69.0.1.input-01-not
26 bit OUT FALSE hm2_7i95.0.7i69.0.1.input-02
26 bit OUT TRUE hm2_7i95.0.7i69.0.1.input-02-not
....................

That jack look OK but your schematic shows a CT pin which would only apply to
a jack with built in transformer, so its very likely you have the jack pinout wrong
(the pinout of the first channel of the 7I74 jack is correct for a single jack)