I managed to link the SMC03A servocontroller board with feedback with a LabVIEW program.
You can find attached the complete source code (VI and SubVIs) that make it working.
I also added a small interface (schematics attached) to the SMC03A in order to implement additional functions to the board and through the Pc serial COM port:
(DTR) ==> Board Power ON/OFF
(RTS) ==> Board Mode Select
(DCD) <== ERROR LED (red)
(DSR) <== STATUS LED (green)
(RI) <== END OF RANGE SWITCHES
(CTS) <== TORQUE LIMIT SWITCHES
(all switches inputs +5V when not activated, 0V when activated)
The interface board is not mandatory to control the SMC03A from LabVIEW since the proposed transistor interface that is described in the SMC03A user manual is sufficient.
The attached LabVIEW code is using VISA functions, this allows it to work with physical COM ports and with virtual COM ports like those you get with RS232-USB adapters.