Hey David,
if you have a router, then it is switched on by the M3 command via the ‘tool-enable’ pin 15 on the 25 pin I/O port (e.g. with a breakout board adapter) of the Onefinity CNC Controller. This works with a relay, e.g. like this one (or with this Remote Control Panel for Onefinity). In this case, the dust collection is turned on by the same ‘tool-enable’ pin 15.
If you have a spindle, it is switched on by M3 command too, but then this is done via the ModBus serial communication port (pin 13 and 14 on I/O port) which is attached to the VFD (the ‘tool-enable’ pin 15 does not work then). Devices that are supposed to run when spindle is running, like dust collection and spindle coolant pump, are then not switched on by the CNC controller, but by the VFD instead, which has output terminals specially made for this purpose. How to connect this is described in the manual of your VFD.
If your question targets whether there is a ModBus command that the Onefinity Controller sends out specifically to turn on dust collector, the answer is no. But this is not necessary, since usually you would always want the dust collector to run as long as the spindle runs, which is the case if you hook the dust collector to an intelligent output terminal of the VFD. However on good VFDs, you can modify the behaviour of the output terminal that controls the dust collection or the spindle water coolant pump. You could insert a delay so that the coolant pump keeps running for a while after the spindle was shut down, or that the dust collection only switches on after spindle reached the set speed.
By the way, the Onefinity Controller is however able to carry out M7, M8, and M9 commands for turning workpiece coolant on, it does this with the L1 and L2 outputs on the back of the controller (pins 2 and 1 on I/O port), to which you can hook a relay with your workpiece coolant system.