6009 digital input gives output

[TobiasD]

Hello,

I'm having a problem with my NI 6009 device. It is connected to a EASYmx Pro V7 board with input and output pins (6 output and 4 input).

With these input pins i want to read the LED's of this board. P0.0 is connected and labeled as input in MAX and in my VI and works properly. The same for P0.1.

My problem are the P0.2 and P0.3 pins. They are connected exactly the same way as the other 2 pins for reading the LED's but they have an logical 1 output when i give them the "input property" (MAX shows the input property of those pins as logical 1 and LabVIEW just reads a true when connected). After changing them of input to output and turning the output to 0 they switch back to 1 as soon as i hit the start button.

Best regards,

TobiasD

[gregorelectric]

Hello Tobias,

I found this Document which describes your Issue. You have to scroll down a little bit.

Can I Use a Pull-down Resistor to Set the Default State of the Digital Lines on my NI DAQ Device?

http://digital.ni.com/public.nsf/allkb/B4FED0C879BD155F862569ED00142DC7

There it says:

USB-6008/6009/6501
These USB devices have a default power-up state of logic high because they have an internal pull-up resistor. Attaching an external pull-down resistor will not yield a logic low start up state. To achieve a logic low state at power-up, use an inverter on each line to fully invert the logic of that particular line. The logic of that particular line is now inverted for all operations that the inverter is used.

If programmable power-up states are desired look into an M series device such as the USB-625x.

Note: Because the internal pull-up resistor on these USB devices is small (4.7 kΩ) to pull the voltage below 0.8V, a pull-down resistor of 850 Ω or less is required. With such a small resistor  ~6 mA will be pulled from the device when driving the line high with no load connected. Since the device can only supply up to 8.5 mA, that only leaves ~2.5 mA for the load.  It is therefore not recommended to use this method to pull the voltage down to a low state.

Gregor

[TobiasD]

If it really is like that why do 2 of my pins work like they should. I already connected 2 pins to 2 led's so i could read those led's. Those pins don't activate my led's unlike my other pins (if those pins are in their "read" state).

[mikebike]

I use the USB-6501 and I have a similar problem. The 4,7 kohm pull-up resistors cause problems during start-up and if/when the computer loses contact with the device.

The data sheet says that the Power-on state is "Input (high impedance)"

4,7 kohm is not high impedance!

[johnsold]

I agree that it is a bit misleading.  I think that statement is intended to mean "Device is configured as an input, including the 4700 ohm pullup resistor to +5 V, and the output drivers are disabled."  In the absence of the pullup resistor the disabled output driver would be high impedance.

Lynn

[mikebike]

Next problem:

The outputs seem to be open-drain as default. Is there a way to make them push-pull with the NI-DAQ software?

[gregorelectric]

Hey Tobias,

first thing is, doing some research by yourself:

https://www.google.de/search?q=ni+6009+push+pull&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:de:official&...

second: please open a new thread for a new topic

thrird: here is your answer:

Configuring NI Devices to be Open-Drain (Open Collector) or Push-Pull (Active Drive)

http://digital.ni.com/public.nsf/allkb/D9B4018C3E540CE4862570F30068C0DB?OpenDocument

[mikebike]

"The Configuration utility can be found in the NI-DAQmx Base folder (typically Hard Drive»Applications»National Instruments»NI-DAQmx Base"

There is no NI-DAQmx Base in my computer.

And "Properties" is not active (for my USB-6501).

Because of the stupid 4.7 kohm pull-ups, I have added 1 kohm pull-downs on two channels that must be low during start-up and when the computer is not in control.

The actual application is configured for push-pull, but I need to verify that my solution works before I ship the equipment.

My only tool is the NI-DAQ and I'm just the hardware guy....

[AnalogKid2DigitalMan]

Another solution-

Use TTL inverters (7404) or equivalent or even transistors for the critical output lines.

-AK2DM

[mikebike]

That's a bad solution!

Redesigning two pcb's will cost a lot of money, and replacing the already delivered units will cost even more...

We have gone from PCI-card to USB-interface, but these stupid pull-up resistors is not exactly an upgrade.