USB 6501 4.7k pull up resistors

[gfsgfdsgsgfds]

I'm able to drive the outputs of a 6501 in push pull but how do I turn off the 4.7k pull up resistor when a pin is used for input?

[mallorim]

Hello,

I do not believe that you are going to be able to turn off or remove the pull up resistor. While this should not be a problem, if you have any concerns, you could post back and explain your circuit and application, perhaps we could help set you up with some sort of work around.

Regards, Mallori M.

[gfsgfdsgsgfds]

Hi, I believe I have a work around but will describe the situation. I'm wanting to drive pins and readback the result. Odd pins are configured to write (push pull) and even to read. All pins had a 1.2k resistor in series and pairs of pins, e.g. 0.0 and 0.1, have their resistors joined (so there was 2.4k between 0.0 and 0.1). The junction of the pair of resistors is the test point.

With the above arrangement the internal 4.7k pullup resistor on 0.0 raises the input voltage to about 1.8V which is sometimes interpreted as a 1. I've dropped my resistors to 330 ohm and that is satisfactory.

With many micro controllers the pullup is switchable and I was hoping it was so with the 6501 but I guess not.
Thanks,
Ken.

[RWatkins]

At this point, the cost of the USB-6501 is about $100, and it costs my client about that for one hour of my services.  Warranty on these devices is a non-issue.  The 4.7K resistors have been pulled for one USB-6501 in an ESD safe workstation with appropriate tooling.  The board has been cleaned with alchohol to remove flux residue, and dried.  We are ready to install weaker pull-up resistors if appropriate.  What is needed now is to know what is appropriate.  I redirect the question:

Are the weak pull-up resistors enabled in the microcontroller in the USB-6501?  This impacts my choice of pull-up resistor replacements.

Roger Watkins

roger@pervalidus.com

[mallorim]

This is a duplicate post. Please refer to this link for further information.
In order to maintain the forums in an orderly manner and to keep problem solutions and information in a consolidated fashion easily searchable by customers, duplicate posts are often linked. Best of luck in future applications.