NI USB 6008 how to make power on outputs (DIO) low during startup

[AlanArmstead]

Hello,
The USB-600x devices do not have the ability to set power up states on digital lines.  As seen in the following KB, they have internal pull-up resistors.  If you want these to power up low, you could add external pull down resistors to offset the internal pull-up resistors. 
-Alan A.

[WM_John_Weeks]

Thanks, Alan. That's good to know.

The User's Guide talks about the pull-up resistors; it doesn't mention the implication that you can't set power-up states.

[Jonathan_Brumley]

The 6008 doesn't support setting a power up state for the digital lines.

This feature is supported by the industrial digital DAQ series (PCI/PXI 651x and 652x).

[AlanArmstead]

M Series DAQ devices support power-up states as well;)

-Alan A.

[Salac]

But, if I put pull-down resistor for pull-up compesation I can not work with digital output. USB-6008 goes in high impedance at power on. If I put pull-down R I can solve the problem that digital output are not high at power on, but when I want to use digital ouput for application, I can not any more put digital output high. If You solve this, please send me a scheme.

[Erik_J]

Hi Salac,

The 6008 has a 4.7kOhm pull up resistor internal to the device causing the behavior that you are seeing. However, attaching another "pull-down" resistor is not the answer to achieve a logic low start up state.  Attaching a pull down resistor to the 6008 will essentially create a voltage divider and will cause the device to not work properly.  You have two options that you can go with to obtain a low start up state.  You can either put an inverter on the lines that you need to start low.  Or you can look into another board that does support programmable power up states (such as the PCI 6503, or other devices that support user defined power up states).  Hope that clears up things a bit, feel free to post back if you have any other questions.

Regards,
- Erik

[Santaprene]

Properties are greyed out, is this a "light" version feature?

[Erik_J]

Hi Santaprene,

The Properties for a device allows you to do two things: set a RTSI Configuration and select an Accessory.  The USB-6008/6009 do not have pins for a RTSI cable and they cannot be used with an accessory, so the Properties are greyed out.

Have a nice weekend,
Erik

[finistere21]

We've got a USB-6008, ended up pulling out the 4.7K ohm pull up resistors on our input DIO lines, and wiring in a 820 ohm pull down. Problem solved. ...We just can't change them to outputs without undoing our modification.

[danielegiraud]

I've solved the problem using shottky diodes, resistors and one transistor.

I sacrificed the last one output to drive a small NPN transistor.

@ power on outputs goes high and 2N2222A clamp then low.

Turning off the transistor, other channels DIO can work as input or output without problem.