It appears these two will not work together unless someone figured out how. The G540 uses pulled up, digital inputs which you "ground" to activate.

The C3, uses pulled up output as well, before the hex inverted schmidt trigger. I even tried a NPN Transistor to sink to ground the output of the C3 when it went high, on a volt meter it looked fine. On a frequency meter it looked fine, but the G540 still would not see it.

I ended up moving the C3 over to a second BOB and it worked flawlessly.