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Digitally controlling resistance between GPIO pins
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imagiko:
I am looking to electrically control the resistance between two points that will each be connected to a GPIO pin. I also want to have the option of keeping the points "open".

My idea to achieve this is to use a digital rheostat such as this one from AD:
https://www.analog.com/media/en/technical-documentation/data-sheets/ad5241_5242.pdf

To keep the points open, I think I should use a MOSFET as a switch (one on each GPIO line) to bring the resistance in and out between the GPIOs. Although I am not entirely sure if I should use a p or n channel MOSFET here.

Is this a decent way to achieve an open circuit and a finite, digitally controlled resistance between two GPIOs? Thanks!
ejeffrey:
Yes, a digital pot is a perfectly good way to do this.

To open circuit use an analog switch instead of a single mosfet.
imagiko:
I want to use two MOSFETs, one on each terminal as I want to electronically bring the resistance in and out
mvs:

--- Quote from: imagiko on October 21, 2018, 08:10:52 pm ---I am looking to electrically control the resistance between two points that will each be connected to a GPIO pin. I also want to have the option of keeping the points "open".

--- End quote ---
It sounds a bit odd. May i ask, why do you need programmable resistance between two digital pins?


--- Quote ---To keep the points open, I think I should use a MOSFET as a switch (one on each GPIO line) to bring the resistance in and out between the GPIOs. Although I am not entirely sure if I should use a p or n channel MOSFET here.
--- End quote ---
Source of the MOSFETs will be floating between rails of GPIOs. How do you plan to controll this MOSFETs (apply gate-source voltage)? Isolated control circuit with own power supply?
Analog switch (74HC4066) is IMHO a better solution here.


--- Quote ---Is this a decent way to achieve an open circuit and a finite, digitally controlled resistance between two GPIOs?
--- End quote ---
There are always some leakage and capacitance in semiconductors... You need to define "open circuit".
SiliconWizard:
Yeah. Tell us what exactly you want to achieve, so we can tell you how you can do without it. ;D
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