"Connection timed out"

[Danny Miller]

I used libmodbus for an older LinuxCNC 2.7 on preempt-rt to talk to an X200 VFD through an Adam isolated 232-485 converter.  That worked.

Changing to a fanless NUC with LinuxCNC 2.8 on Debian.  It also has a built-in RS232 serial DB9.  Just one slave device, ID#1.  But LinuxCNC can't see the VFD.  If I launch LinuxCNC from a terminal, the text output says  Modbus Connection Timed Out.

 I scoped these.  libmodbus is able to send out, correct baud, and get a response from the X200 that passes back through the 485-232 bridge and I can see on the Rx-in on the DB9.  But libmodbus doesn't see the response and times out.

Any idea?

Thanks,

Danny