4
\$\begingroup\$

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.

\$\endgroup\$
  • \$\begingroup\$ Don't forget the reset pin as well as the three address lines, looks like that should be tied high as well. \$\endgroup\$ – PeterJ Aug 24 '14 at 11:40
  • \$\begingroup\$ yup, good catch :) thanks, and thanks for fixing the link, too! \$\endgroup\$ – garph0 Aug 24 '14 at 11:51
6
\$\begingroup\$

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.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.