Hi Syrpimp
On the USB-8451 the SDA and SDL signal lines are open drain with no programmatic pull up ability.
See the NI-845x Hardware and Software manual on page 36 you have the signal descriptions.
In the same manual if you go to page 45 this is the signal descriptions for the USB-8452 this device gives you the ability to programmatically add pull up resistors.
With your current hardware you will either need to provide external circuitry for the pull up / down resistors.
You could if you needed programmatic pull up / down resistors with some external circuitry you could utilise the static DIO on the 8451 to control an external relay.
Hope this helps
James
CLD & CTD
Simplicity AI
