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Does USB 6221 have active output structure or open drain



I am planning to use USB 6221 instead of USB 6501 DAQ in my application. In case of 6501 (open drain) and added a resistor from pin to gnd (4.7K pull up already present in 6501) to convert 5v digital signals to 3.3V digital signals. I couldnt find the output structure of 6221. Is it open drain or active push-pull. (first option - same as 6501, second option : i need a res divider sturcture from the digital pin)


Is there any major difference (compatability-wise) between 6501 and 6221




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Message 1 of 3

Hello Thames,


The USB-6221 only has a range of 0-5V and this is not programmable, so you will need external components to bring it to your needs.

Compatibility-wise, the two devices will not show differences in your project. As soon as you change the physical channels in your DAQmx tasks, you will be able to run your project with no problems.


On a side note, it seems that with every reply we post for you, another forum thread is spawned! All of these questions could have been answered within a few minutes if you called instead of posting on the forums. Hardware related questions can be dealt with by either our Sales Engineers, or our Technical Support. For software related issues you can speak to our Technical Support as long as you have a Support contract, otherwise indeed you can post on our forums. Do you work with a company or a University? Universities normally have access to our Technical Support anyway. Why don't you try calling us if you have another question; if you are in the UK, call 01635 523545 and ask to speak to our Sales Engineers if you have questions on buying a new product, or our Technical Support if you have questions on a product you already have. You will get your answers much quicker!!


In any case, you are welcome to continue posting on the forums if you prefer it.


I hope we help!

Kind Regards,

Michael S.
Applications Engineer
NI UK & Ireland

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Message 2 of 3

The 6221 is active push-pull when used as an output.


When choosing resistor values to divide-down your voltage, keep in mind that the DIO lines have an internal ~50k Ohm pull-down resistor (20k Ohm minimum).

John Passiak
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Message 3 of 3