I'm writing again on the same subject because I realized I was not very clear and i'd like to add some info. sorry but i didn't find a way to edit or delete my previous post.
So... I built a data acquisition system with a laptop (Samsung NC10) and a NI 6009 OEM plus some varius hardware for the measurement. Previously I already built one with the same laptop but a NI 6009 USB and everything was fine. So I'm pretty sure that the signal I'm measuring and the software is ok as well as the general layout of the system.
This time i wanted to integrate the electronics on a very simple pcb board that basically drives around the signals and the USB power and data.
The NI 6009 USB is connected through the 34 pin connector to the pcb board, so _there's no direct usb cable inserted in the NI board_, but the usb cable is connected to the PCB.
This laptop power supply has no ground. If I use this laptop on batteries everything is fine, if i use it with the power supply connected the usb 6009 stops working very often (the led goes off or stay steadly lit). The strange is that if I connect the power line ground to the pcb everything is fine as well.
I got two kind of errors: Status Code: -50405 and Status Code: -50150.
I made different kind of tests and I can now reproduce this problem. Basically you can hang the NI board by touching its ground (I use the usb connector cage) with a random cable (I use a 1 meter normal, free cable. Notghing is attached to it). This does not happen if i use laptop on batteries or i cannect a ground cable to the laptop or pcb. Also it does not happen if I use a standard usb cable connected to the NI 6009.
Thus I feel the problem is usb cable shilding and /or grounding. I was wondering if anybody has a fast solution, i would not prefer to connect the NI board using a standard usb cable neither I would like to ground the system.
Thanks,
michele
