To see if you have the thing configured correctly, turn your computer off and then run it back up. Check the voltage on the two pins. This is the signal at rest. Now switch the signal using the MDI line - just a single command M7.
Your M7 pin should alter status - if it was 0v it should be 5v - if it was 5v it should be 0v. If it has not moved, then your configuration is wrong.
Allocate M7 to an Output say #3, (Ports and Pins/Spindle setup) then allocate the output to a pin.(Ports and Pins/Output signals)
Do the same with M8 using #4
M7 should turn one on, M8 should turn the other on and M9 should turn both off.