Hi,
some of the advantages I mentioned of using an external controller like an ESS is that it has three 'ports' worth of IO.
Its normal to have pins 2-9 of port 1 as outputs for your motor drivers. You can however have pins 2-9 in ports 2 &3 as inputs instead
of the more usual outputs. Thus an ESS set up this way has:
Outputs 2-9,1,14,16,17 port1
1,14,16,17 port2
1,14,16,17 port3
total 20 outputs
Inputs 10-13,15 port1
2-9,10-13,15 port2
2-9,10-13,15 port3
total 31 inputs
You can have quite a sophisticated machine with this number of inputs and outputs. The PoKeys E57 or U57 boast even more, some of which can be
used as analogue inputs reporting back to Mach via Modbus.
There is now quite a range of external motion controllers and the mature and seasoned manufacturers producing some very capable gear light years
ahead of the parallel port.
Craig