im working on a project which requires alo i/o pins. For that reason i bought a pcf8574P 8bit I/O expander which uses the I2C protocol. The problem is how to combine the Rasp PI and the arduino.

For example:

I want the Rasp to send data to the Arduino. Currently i'm using serial but i wanted to switch over to I2C because it better, simpler, and faster however how can i use 2 I2C when the Atmega 328P supports only 1 I2C bus?

The plan goes like this:

The PI is master of the arduino and it sends the data. Arduino is the slave

Arduino is master of the IO expander and the expander is slave

Possible solutions:

  1. Use the Serial protocol to send the data and use the I2C for the expander
  2. Make the arduino master of the PI and the expander which i'm not sure if its possible

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