I can't externally latch the pins on the parallel port (from a 5 volt source). Does anyone know why this could be??

I am using visual basic to interface w/ the parallel port through Inpout32.dll. I have no problem outputting a high or low from visual basic but when I try to latch the pins externally (5 volt source) they won't change state let alone latch to the state I set them to. Any help would be greatly appreciated.

thank you.

 

You have to ground the pins using the lpt gnd pins 18-...(the pins are ttl high normally) you can use a pullup resistor of 10k 0r so but not usually nesecary (one side of the resistor to the pin side of your contacts, the other to your 5v source). This ensures a ttl high. dont forget the status bit is base +1 eg 0x0379 and the busy pin is inverted logic

 

Sorry, now that I read this I realize I was unclear as to what I want. I am trying to swith the data pins between send and recieve mode useing the program not an external input.