I need more pins on my raspberry pi 3 so that I can use it to manage the lights in my house. I am going to use relays and MCP23017. I need to know how to use 8 of the MCP23017 on my raspberry pi. If you can I also need to know how to use them in python to go in and out like normal.

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    I need help as much as i can get. Feb 1, 2020 at 23:51
  • What do you mean by "help as much as possible"?. The following posts in relay and mcp23017 might take you hours to just skim through: (1) KY-019 2108/2019 posts by tlfong01 raspberrypi.org/forums/viewtopic.php?f=37&t=77158#p1323061, You can also search in rpi.org forum for as much more help as possible. Examples: (2) Search "ky-019" "tlfong01" to get 371 matches, (2) Search "mcp23017" "tlfong01" to get 178 matches. Happy learning and making. Cheers.
    – tlfong01
    Feb 2, 2020 at 2:10

1 Answer 1


You connect pin 12 SCL and pin 13 SDA in parallel to RPi pin 3 SCL & pin 5 SDA.

So the MCP23017 are daisy chained.

You can run up to eight in parallel by setting the A0/A1/A2 pins to a different 3-bit binary value on each MCP23017.


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