I am using MCP23017 as a GPIO expander with Arduino in my project. I have too many serial devices and no pins left on Arduino for UART communication.

I am wondering if I can use this MCP23017 GPIO expander pins for UART communication or not?

  • 1
    with SoftwareSerial? no
    – Juraj
    Jul 23, 2020 at 9:33

2 Answers 2


I can think of one way.

In theory you could use the GPIO pins of the mcp23017 to control a couple of 2-way multiplexers. With these multiplexers you could split your Rx/Tx pins to more than one serial bus.

May it be obvious that you cannot used the split busses at the same time. So depending on your specific use-case this may or may not be a solution.


No. No you can't. Serial takes precise timing and fast reactions. Things you can't do with a remote device like that.

Instead there are SPI UART devices specifically for the job, such as the MAX3107.

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