Welcome to LinuxCNC.org

Still curious about how the power supplies for the board work.

But by adding sserial_port_0=20000000 to the config, it magically starting working. Is it too early for a beer already?

5V power _never_ comes from field power
W1 must always be in the left hand position unless you apply external 5V to the 7I76
W2 must be in the left hand position if you want the _field_ logic power and field I/0 power to be the same


what was the sserial_port_0 line before?

Thanks for the explanation! I don't post on forums, but when I do, I'm desperate...

Used to be:
CONFIG="num_stepgens=3"

Now it's:
CONFIG="num_stepgens=3 sserial_port_0=00000000"

Strange though. All of the 7i76 I/O showed up as autodeteced, but it just didn't work. Now it works. *shurgs*

Yeah you are supposed to need the serial_port_0=whatever line
maybe it takes serial_port_0=XXXXXXXX to disable them (driver bug?)

Apparently that is the standard default behavior, that is when modules are not mentioned in
the config line that all such modules are enabled. So it is expected behavior, other than not working.
I suspect there may be a driver bug where if the config string is missing invalid modes get requested
or some such.

Andy Pugh has fixed this error (Thanks Andy!)

Now a missing sserial modparam (the "sserial_port_n=something")
is the equivalent of specifying "sserial_port_n=00000000"