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I'm a total newbie fooling around with a project of mine.

I want to use an MCP23017 I2C port extender (Data sheet) for my Arduino project.

The chip has three hardware pins that must be externally biased.

I apologize if the question is silly, but, can I just connect the pins to V+ or GND, or do I need to put a resistor in series to limit the current? I looked around a bit but I wasn't able to find an answer.

guyfleeman
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garph0
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1 Answers1

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Yes you can directly connect these pins to GND or V+.

The reason you did not find this explicitly stated is that it is standard that a high-impedance digital input can be connected directly to a logical 0 or 1. When a resistor was needed this would be stated explicitly.

Using a resistor instead of a hard connection might be convenient when you need to change the address on a finished PCB: you can short the pin to the opposite supply rail without damaging anything.

Wouter van Ooijen
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  • _"Using a resistor instead of a hard connection might be convenient..."_ This is often a zero-ohm link/resistor which doesn't impose significant resistance but is useful for its standard form factor. – Benjamin Crawford Ctrl-Alt-Tut May 08 '20 at 19:58